1

Electrooptic Logic AND Gate Using a

Single Microring Resonator

M. Rakib Uddin*, Hafizuddin Helmi, Nur’azmina Lingas and Zainidi Haji Abdul Hamid

Electrical and Electronic Engineering Programme Area, Faculty of Engineering

Universiti Teknologi Brunei (UTB), Gadong, Brunei Darussalam

*rakib.uddin@utb.edu.bn

Abstract - In this paper, an electrooptic logic AND gate is

demonstrated using a single microring resonator. The

main principle of the logic operation is the resonant shift

due to the electro-optic effect which is responsible to

change the effective index of the device material. The

logic operation is justified by simulation with gate output

in the domain of optical spectrum as well as timing

diagrams. Extinction ratio of about 30 dB was recorded

from the gate output spectrum. Timing diagrams test

was performed with a 10 Gbps digital input signal and a

clear AND output was achieved.

Keywords- Silicon photonics; micro-ring resonator;

Photonic AND gate.

I. INTRODUCTION

Photonic technology in computing is important for

future high speed computers and communications [1], [2]. In optical signal processing, like other photonic devices and circuits, optical logic gates have also received considerable attention [3]-[5]. In the field of photonic computer and communications, the logic units are the main building blocks and in communication networks they can enable many advanced functions such as all-optical bit-pattern recognition, all-optical packet header and payload separation, all-optical bit error rate monitoring, all-optical label swapping, all-optical packet drop and so on. Microring resonator has potential applications in photonic computing. In references [6], [7] electro-optic logic gates are demonstrated using microring resonator; however, they used two cascaded rings to achieve the basic logic functions. In this paper, we propose a quite simple circuit using a single mirroring resonator instead of two cascaded rings to get logic AND logic functions. We design, simulate and demonstrate the results of logic AND gate. The gate is designed using a single micro ring resonator. The gate operation is verified by the optical spectrums as well as by the waveforms of 10 Gb/s data inputs.

II. PRINCIPLE OF OPERATION

A micro-ring resonator with external voltage

applied exhibits a property of resonant shift [8], [9]. These changes can be achieved by various methods and amongst all methods, the convenient and instant method is the electric fields passing through the

materials which in turn causes an electro-optic effect, i.e., the material index changes and then the resonance is shifted. Using this behaviour, logic AND gate function is demonstrated. The schematic of the logic circuit using a single ring along with the symbol and the truth table of AND gate is shown in Fig. 1.

Optical Input Optical Gate Output

Gate Inputs (Electrical)

A B

A B Output

0 0 0

0 1 0

1 0 0

1 1 1

A

B Output

(a)

(b) (c)

Fig. 1 The schematic of the logic circuit using a single ring along with the symbol and the truth table of AND gate.

Fig. 1 (a) is the schematic diagram of the single bus waveguide ring resonator. The single bus waveguide microring resonator has only one straight waveguide which has two ports including input port and throughput port. The straight waveguide is closely located with the ring waveguide. The diameter of the ring is dependent on the requirements of the device. The gap between the straight waveguide and the ring is also an important parameter. The coupling coefficient is a function of the gap. The waveguide dimensions are also depends on the design requirements. The typical width of the waveguide is 500 nm and the height of the waveguide is 220 nm. The gap is about 100 nm. An electrical excitation is applied to the ring resonator which is shown by “A, B” in the schematic diagram in Fig. 1 (a). The symbolic diagram of the AND gate is shown in Fig. 1 (b). The truth table of the logic AND functions are shown in Fig. 1 (c). The definition of AND logic is

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the output is logic HIGH only if the inputs are logic HIGH, otherwise the outputs are logic LOW which is shown in the truth table in Fig. 1 (c).

The optical micro ring resonator used for the demonstration in Fig. 1 has a frequency of resonance at λr and with external voltage the resonant shift to λr’. The gate function is based on the resonant shift. The phenomena of the resonant shift is shown in Fig. 2 schematically for different gate voltages of AND operations. When an optical CW light is sent to the ring resonator input port with the wavelength of λr, it gives an optical throughput output with low power, which can be classified as optical logic ‘0’. When sufficient electrical supply is sent to the resonator input port, the ring resonator output optical power increases to the point it can be considered as logic ‘1’.

In Fig. 2 (a), it is shown schematically that for the voltage inputs 0, 0; the resonant shift is not sufficient; So that the optical output is low and is it considered as logic “0”. In Fig. 2 (b), it is shown that for the voltage inputs either 0, 1; or 1, 0; the resonant shift is not sufficient too; So that the optical output is low and is it considered as logic “0”. Whereas when both the electrical inputs are high (1, 1), the resonant shift is sufficient which is shown in Fig. 2 (c). So that the optical output is high enough which can be considered as logic “1”. This is the schematic of logic AND gate operation. In the figure (Fig. 2), the wavelengths λr and λr’ represents the original and the shifted wavelength, respectively.

Fig. 2 The schematic of optical spectrum for logic AND function.

Fig. 2 (a) shows the low logic output when both the electrical logic inputs are low, i.e., both are 0s. In this case, both the light wavelengths are located at the same position which means the measured light intensity at the original wavelength and the wavelength due to two electrical inputs A, B as LOW are same as logic LOW. Fig. 2 (b) shows the schematic of logic low output when either inputs is 0 or 1. If only one input is high, it is not enough to shift the resonance enough to get a higher optical power at the output. So, the output is logic low. In this case both the original resonant wavelength and the wavelength due the either A or B logic HIGH are located closely so that the intensity of the light at throughput port is still logic LOW. Fig. 2 (c) shows the 1, 1 operation. When both the electrical inputs are high, the resonance is shifted enough so that the output is high enough to consider the logic high, ‘1’. In this case it is shown that the original resonant wavelength and the wavelength due to the excited A, B are located at different location which makes sure that the light intensity at the original resonant point is high enough compare to the other three cases. This high intensity is

considered as logic HIGH. In all three figures in Fig. 2 the two dotted lines represent the two logic inputs. Base on this principle, we design our logic device in the simulation environment using a commercially certified software called “Lumerical (www.lumerical.com). In the software, there are four modules. We used the module, “INTERCONNECT” to design and simulated the logic operation of the AND gate based on a single photonic microring resonator. The justification of the logic operation in spectrum domain as well as using timing diagrams are conducted using this software which will be described in the following sections with output results. The design of light source, the ring resonator, electrical signals and the optical spectrum analyser were performed using the same “INTERCONNECT” environment.

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III. LOGIC SIMULATION AND RESULTS

Fig. 3 shows the photonic AND gate input-output

with optical spectrum. A commercially certified simulation software called “Lumerical Solutions” [https://www.lumerical.com/] was used to simulate the logic function. The spectrum results in Fig. 3 show

that the optical intensity is LOGIC HIGH only when both the inputs are LOGIC HIGH which is the truth of AND gate. For four conditions (00, 01, 10, 11), the output intensities are -18 dB, -23 dB, -18 dB and 10 dB. 10 dB is logic high whereas -18 or lower dBs are logic low. So, output is LOGIC HIGH when

-120

-100

-80

-60

-40

-20

0

20

1547 1548 1549 1550 1551 1552 1553

Outp

ut

Po

wer

(d

Bm

)

Wavelength (nm)

0,0

-120

-100

-80

-60

-40

-20

0

20

1547 1548 1549 1550 1551 1552 1553

Outp

ut

Po

wer

(d

Bm

)

Wavelength (nm)

0,1

-120

-100

-80

-60

-40

-20

0

20

1547 1548 1549 1550 1551 1552 1553

Outp

ut

Po

wer

(d

Bm

)

Wavelength (nm)

1,0

-120

-100

-80

-60

-40

-20

0

20

1547 1548 1549 1550 1551 1552 1553

Outp

ut

Po

wer

(d

Bm

)

Wavelength (nm)

1,1

≈ -23dBm

≈ 10dBm

≈ -18dBm

≈ -18dBm

Fig. 3 Simulation results: AND logic output in spectrum domain.

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Fig. 4 Simulation results: AND logic output timing

diagrams.

both inputs are high which is the AND gate truth

function. The spectrum results in Fig. 3 were

measured by the simulation and recorded using the

optical spectrum analyser. The input light was set to a

single wavelength light source to fit a certain resonant

wavelength. Fig 4 shows the timing diagrams of the

AND gate outputs simulated by the software. The

AND gate output was recorded using the through port

of the ring resonator. The timing diagrams also

verifies the AND operation. In Fig. 4, “A” and “B” are

the input waveforms and “AND” is the output. In the

figure it is shown that when inputs are 0, 0, the output

is “0. When inputs are 1, 0, or 0, 1, the output is

also“0”. When both inputs are 1, 1, the output is “1”

which are the truth functions of AND gate.

IV. CONCLUSION

In this paper, we have simulated and demonstrated a

novel scheme of digital micro-photonic logic gate

based on the opto-electronic effect in silicon photonic

micro ring resonator. The AND logic functions were

verified by both the optical spectrum and digital data

signal at the rate of 10 Gbps. Both the optical

spectrum and the digital waveforms, proved the AND

logic operation using a single micro ring resonator. It

is noted that the optical micro-ring resonator can be a

promising micro device for photonic logic design.

Since the AND gate is the basic logic gate, it can be

the basis for the micro-photonic digital building

blocks for future optical computers and

communication applications.

ACKNOWLEDGEMENT

The authors gratefully acknowledge use of Graduate

Studies and Research Office Grant [UTB/GSR/1/2016

(1)] at Universiti Teknologi Brunei (UTB), Brunei

Darussalam.

REFERENCES

[1] H. J. Caulfield and S. Dolev, “Why future supercomputing requires optics,” Nat. Photon., vol. 4, pp. 261–263, 2010. [3] D. A.

B. Miller, “The role of optics in computing,” Nat. Photon., vol. 4, p.

406, 2010. [2] D. A. B. Miller, “The role of optics in computing,” Nat. Photon.,

vol. 4, p. 406, 2010.

[3] H. Yoo H. J. lee, Y. D. Jeong, and Y. H. Won, “All-optical logic gates using absorption modulation of an injection-locked Fabry-

Perot laser diode,” in proc. Photonics in Switching, Greece, Oct. 16-

18, 2006. [4] M. R. Uddin, J. S. Lim, Y. D. Jeong and Y. H. Won, "All-optical

digital logic gates using single-mode Fabry-Perot laser diodes,"

Photonics Technology Letters, IEEE, vol. 21, no. 19, 2010. [5] G. Berrettini, A. Simi, A. Malacarne, A. Bogoni, and L. Poti,

“Ultrafast integrable and reconfigurable XNOR, AND, NOR, and

NOT photonic logic gate,” IEEE Photon. Technol. Lett., vol. 18, no. 8, 2006.

[6] Y. Tian et all, “Simulation and Demonstration of Directed

XOR/XNOR Logic Gates Using Two Cascaded Microring Resonators”, IEEE Photon. Journal, vol. 8, no. 2, 2016.

[7] Y. Tian et al., “Electro-optic directed AND/NAND logic circuit

based on two parallel microring resonators”, Opt. Express, vol.20, no. 15, 2012.

[8] M. Elshoff and O. Rauntenberg, "Design and Modelling of Ring

Resonators used as Optical Filters for Communications Applications,"

Universidad Publica de Navarra, Pamplona, Spain, 2010.

[9] M. Rakib Uddin, and Y. H. Won, "Rib Waveguide-based Athermal Micro-ring Resonator", Optical and Quantum Electronics, Vol. 47, No. 8,

2015.

5

Design of a Half-bridge Synchronous Rectifier with

Current Doubler Resonant Converter for Optimizing

Solar Powered Surveillance System

Ryann Alimuin1, Elmer Dadios2, Aldrich Guiron1, Ramon Asio1, Paul Joshua Miranda1, Razelle R. Vale1 and

Christian John Fernandez1 1Technological Institute of the Philippines – Quezon City

2De La Salle University - Manila

ryann.alimuin@tip.edu.ph, elmer.dadios@dlsu.edu.ph

Abstract — the power optimizer utilizes a resonant converter

which is integrated in a surveillance system. The resonant

converter has a low input voltages boost (increase) and high input

voltages buck (decrease) characteristic for a target specification of

12V. The power optimizer has also a bidirectional property where

it allows the charging of the battery while supplying the load.

Power optimization was achieved through synchronous

rectification in which the losses were significantly reduced since

MOSFETs are used for fast switching. The results show that the

peak efficiency is at nominal at 12V. The efficiency of the power

optimizer was evaluated with varying loads. For an 8V supply

input, the efficiency ranges from 56% to 80%, at 12V input, it

ranges from 54% to 98% and at 17V input ranges from 45% to

98% with load variation from 1Ω to 1000 Ω.

Key Terms: Current Doubler, Load Variation, MOSFET, Power

optimization, Resonant, Resonant converter

I. INTRODUCTION

Power supply has been doing a vital role in each and every

machinery and electronic equipment because it powers up the

whole system. Studies show that using the right and the best

power supply for the system is most important while using the

wrong power supply in the system can lead to major problems

like shortening the lifespan of the system, and worst case, can

destroy the whole system. The most commonly used power

supply nowadays is the Switch Mode Power Supply (SMPS). It

was invented to overcome the disadvantages of the linear power

supply such as large power loss due to the use of large electronic

equipment. Linear Mode Power Supply can only be used as a

step-down regulator, unlike the SMPS, it can step-up and step-

down the voltage. It can convert the input voltage into higher

one or into lower one. SMPS are used especially to have high

supply efficiency for high power application, and to maintain

the lifespan of the battery and its external temperature.

However, the problem in using SMPS which uses Pulse Width

Modulation (PWM) is its hard switching characteristic that is a

major cause of the switching loss [1].

Figure 1 shows the difference in losses between hard

switching and soft or resonant switching.

Figure 1. Current and Voltage waveforms of Hard and

Resonant Switching [2]

Resonant converters are DC-TO-DC designed to overcome the

disadvantages of conventional converters. To achieve high

power density, converters must be designed with high

frequency. Conventional converters can achieve high efficiency

compared to linear but the problem is when the switching

frequency increases also the losses increases due to switching

frequency. Resonant converters can overcome the

disadvantages of the conventional converters because of its

ability to achieve high efficiency by soft-switching. It is

classified into three types Conventional Converter, Quasi-

resonant Converter and Multiresonant Converter (shown in

figure 2).

Figure 2. Classification of Resonant Converter [3]

Resonant converter can overcome the problems with the other

SMPS topologies. Using the soft-switching technique it can

6

reduce losses and can generate EMI better performance. With

the use of synchronous rectification, the efficiency of the typical

resonant converter can be raised more. Synchronous

rectification with current doubler is used to reduce switching

and conducting losses of active switches. Converter operating

at resonant mode can have improved efficiency because the

impedance between input and output are at its minimum [3].

II. FUNCTIONAL DIAGRAM OF THE POWER OPTIMIZER

UTILIZING RESONANT CONVERTER

The power optimizer includes the switching, the resonant

converter circuit, and the rectifier / filter. Soft switching

technique will be used which reduces the possibility of having

very high loss in electronic switches. It is usually a state of Zero

Voltage Switches (ZVS) or Zero Current Switches (ZCS) that

increases the conversion efficiency within power electronics

topologies [3]. The resonant converter circuit uses equal

capacitance and inductance to enhance the wave formation of

either the current or the voltage through the switching

component thus, no power dissipation when switching happens

due to ZVS or ZCS. Rectifier and filter part are used to

smoothen and to have a steady or stable DC voltage output.

Once the power optimizer is placed, the energy harvested from

the solar panel to the battery will be maximized and achieved a

much higher efficiency [4].

Figure 3. Functional Diagram of the Power optimizer

The functional diagram of the power optimizer is shown in

figure 3. First, the input of the converter which is from the solar

panel will be monitored by the voltage sense of the MOSFET

DRIVER. If the sensed voltage is lower than the intended output

voltage, the converter will perform boost mode, while buck

mode will be perform when the output voltage is higher than the

intended output voltage. The buck and boost mode has a

characteristic of synchronous switching which will help to

make a resonant conversion [6]. Regulated output will be done

by filtering the voltage output to lessen the voltage ripple, the

current doubler placed at the end of the converter is used to

provide a lesser voltage ripple [4]. The power optimizer also has

a feature of bidirectional switching [3]. When the output that

from the converter is enough, it will simultaneously supply the

battery and the camera. The bidirectional circuit is also

responsible for monitoring the output voltage of both converter

and battery, and also to ensure that the power that would be

powering up the load will be coming from either of the two that

which has higher voltage output.

III. DESIGN MODELLING OF THE POWER OPTIMIZER

The following equations are used to solve for the parameters of

the resonant converter to provide an efficient power optimizer.

Output power based from target efficiency

PO in Watts

𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) =𝑃𝑜

𝑃𝑖

The value of the output voltage and current based from the

target efficiency must be generalized.

VO = in Voltage

IO = in Ampere

Soft-start Capacitor

When the RUN pin voltage is higher than 1.5V, an internal

1.2µA current source charges soft-start capacitor CSS at the SS

pin. The ITH voltage is then clamped to the SS voltage while

CSS is slowly charged during start-up. This “soft-start”

clamping prevents abrupt current from being drawn from the

input power optimizer. [3]

𝑇𝐼𝑅𝑀𝑃 = 𝑅𝑈𝑁 𝑝𝑖𝑛

1.2 𝜇𝐴−𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑠𝑜𝑢𝑟𝑐𝑒∗ 𝐶𝑆𝑆

Frequency Synchronization and Frequency Setup

The phase-locked loop allows the internal oscillator to be

synchronized to an internal source via PLLIN pin. To set the

frequency of the power optimizer, the PLLFLTR pin should

have an input voltage from 0 V to 2.4 V. [3]

Inductor Selection

𝐿𝐵𝑂𝑂𝑆𝑇 >𝑉𝐼𝑁(𝑀𝐼𝑁)

2 ⋅ (𝑉𝑂𝑈𝑇 − 𝑉𝐼𝑁(𝑀𝐼𝑁)) ⋅ 100

𝑓 ⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋) ⋅ %𝑅𝑖𝑝𝑝𝑙𝑒 ⋅ 𝑉𝐼𝑁(𝑀𝐴𝑋)

7

𝐿𝐵𝑈𝐶𝐾 >𝑉𝑂𝑈𝑇 ⋅ (𝑉𝐼𝑁(𝑀𝐴𝑋) − 𝑉𝑂𝑈𝑇) ⋅ 100

𝑓 ⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋) ⋅ %𝑅𝑖𝑝𝑝𝑙𝑒 ⋅ 𝑉𝐼𝑁(𝑀𝐴𝑋)

𝐑𝐒𝐄𝐍𝐒𝐄Selection and Maximum Output Current

𝐼𝑂𝑈𝑇(𝑀𝐴𝑋,𝐵𝑂𝑂𝑆𝑇) = (160𝑚𝑉

𝑅𝑆𝐸𝑁𝑆𝐸−

∆𝐼𝐿

2) ∙

𝑉𝐼𝑁(𝑀𝐼𝑁)

𝑉𝑂𝑈𝑇

𝐼𝑂𝑈𝑇(𝑀𝐴𝑋,𝐵𝑈𝐶𝐾) = (130𝑚𝑉

𝑅𝑆𝐸𝑁𝑆𝐸+

∆𝐼𝐿

2)

BOOST MODE:

𝑅𝑆𝐸𝑁𝑆𝐸(𝑀𝐴𝑋) =2 ∙ 160𝑚𝑉 ⋅ 𝑉𝐼𝑁(𝑀𝐼𝑁)

2 ⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋,𝐵𝑂𝑂𝑆𝑇) ⋅ 𝑉𝑂𝑈𝑇 + ∆𝐼𝐿𝐵𝑂𝑂𝑆𝑇 ⋅ 𝑉𝐼𝑁(𝑀𝐼𝑁)

BUCK MODE

𝑅𝑆𝐸𝑁𝑆𝐸(𝑀𝐴𝑋) =2 ∙ 130𝑚𝑉

2 ⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋,𝐵𝑈𝐶𝐾) − ∆𝐼𝐿𝐵𝑂𝑂𝑆𝑇

𝑪𝑰𝑵 and 𝑪𝑶𝑼𝑻Selection

𝐼𝑅𝑀𝑆 ≈ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋) ⋅𝑉𝑂𝑈𝑇

𝑉𝐼𝑁⋅ √

𝑉𝐼𝑁

𝑉𝑂𝑈𝑇− 1

NOTE: This formula has a maximum at 𝑽𝑰𝑵 = 2𝑽𝑶𝑼𝑻, where

𝑰𝑹𝑴𝑺 = 𝑰𝑶𝑼𝑻(𝑴𝑨𝑿).

𝑅𝑖𝑝𝑝𝑙𝑒(𝐵𝑜𝑜𝑠𝑡, 𝐶𝑎𝑝) =𝐼𝑂𝑈𝑇(𝑀𝐴𝑋) ⋅ (𝑉𝑂𝑈𝑇 − 𝑉𝐼𝑁(𝑀𝐼𝑁))

𝐶𝑂𝑈𝑇 ⋅ 𝑉𝑂𝑈𝑇 ⋅ 𝑓

𝑅𝑖𝑝𝑝𝑙𝑒(𝐵𝑢𝑐𝑘, 𝐶𝑎𝑝) =𝐼𝑂𝑈𝑇(𝑀𝐴𝑋) ⋅ (𝑉𝐼𝑁(𝑀𝐴𝑋) − 𝑉𝑂𝑈𝑇)

𝐶𝑂𝑈𝑇 ⋅ 𝑉𝐼𝑁(𝑀𝐴𝑋) ⋅ 𝑓

The steady ripple due to the voltage drop across the

ESR is given by:

∆𝑉𝐵𝑂𝑂𝑆𝑇,𝐸𝑆𝑅 = 𝐼𝐿(𝑀𝐴𝑋,𝐵𝑂𝑂𝑆𝑇) ⋅ 𝐸𝑆𝑅

∆𝑉𝐵𝑈𝐶𝐾,𝐸𝑆𝑅 = 𝐼𝐿(𝑀𝐴𝑋,𝐵𝑈𝐶𝐾) ⋅ 𝐸𝑆𝑅

Power MOSFET Selection and Efficiency

Considerations

𝑃𝐴,𝐵𝑂𝑂𝑆𝑇 = (𝑉𝑂𝑈𝑇

𝑉𝐼𝑁⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋))

2

⋅ 𝜌𝑇

⋅ 𝑅𝐷𝑆(𝑂𝑁)

where ρT is a normalization factor (unity at 25°C) accounting

for the significant variation in on-resistance with temperature,

typically about 0.4%/°C as shown in Figure 9. For a maximum

junction temperature of 125°C, using a value ρT = 1.5 is

reasonable. [3]

𝑃𝐵,𝐵𝑈𝐶𝐾 =𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇

𝑉𝐼𝑁𝐼𝑂𝑈𝑇(𝑀𝐴𝑋)

2 ⋅ 𝜌𝑇

⋅ 𝑅𝐷𝑆(𝑂𝑁)

𝑃𝐶,𝐵𝑂𝑂𝑆𝑇 =(𝑉𝑂𝑈𝑇 − 𝑉𝐼𝑁)𝑉𝑂𝑈𝑇

𝑉𝐼𝑁2 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋)

2 ⋅ 𝜌𝑇

⋅ 𝑅𝐷𝑆(𝑂𝑁) + 𝑘 ⋅ 𝑉𝑂𝑈𝑇2

⋅𝐼𝑂𝑈𝑇(𝑀𝐴𝑋)

𝑉𝐼𝑁⋅ 𝐶𝑅𝑆𝑆

Where CRSS is usually specified by the MOSFET

manufacturers. The constant k, which accounts for the loss

caused by reverse recovery current, is inversely proportional to

the gate drive current and has an empirical value of 1.7. [3]

𝑃𝐷,𝐵𝑂𝑂𝑆𝑇 =𝑉𝐼𝑁

𝑉𝑂𝑈𝑇⋅ (

𝑉𝑂𝑈𝑇

𝑉𝐼𝑁⋅ 𝐼𝑂𝑈𝑇(𝑀𝐴𝑋))

2

⋅ 𝜌𝑇 ⋅ 𝑅𝐷𝑆(𝑂𝑁)

𝑇𝐽 = 𝑇𝐴 + 𝑃 ⋅ 𝑅𝑇𝐻(𝐽𝐴)

INTVCC Regulator

Use of the EXTVCC input pin reduces the junction temperature

to:

𝑇𝐽 = 70∘𝐶 + 24𝑚𝐴 ⋅ 6𝑉 ⋅ 34∘𝐶 𝑊⁄ = 75∘𝐶

Output Voltage

𝑉𝑂𝑈𝑇 = 0.8𝑉 (1 +𝑅2

𝑅1)

8

IV. CIRCUIT SIMULATION

Integrated circuits are mostly used as the driver for the

circuit. An LTC3780 is used, it is a synchronous controller that

uses combined buck and boost circuit. Each stage is comprised

of two MOSFET switch. An active switch replaces the diode,

which is the MOSFET to make the converter more efficient. An

inductor separates the buck and the boost. This controller can

achieve 98% peak efficiency. It has phase-lockable frequency

of 200 kHz – 400 kHz. A fault protection comparator is and

foldback current limiter is provided inside the LTC3780. [3]

Figure 4. Schematic Diagram of the Circuit for Power

Optimizer

Figure 5. Voltage Sense Switching Circuit (Bidirectional

Circuit)

The bidirectional circuit is shown in Figure 5. It helps the power

optimizer to extend its capability in storing energy to the battery

while supplying the load.

Moreover, series of simulations and testing are needed to

determine if the target specifications are achieved.

Figure 6. Simulation output of the Design

Figure 7. Simulation of the Input and Output Power

The Figure 6 shows the target output power of the design.

Through the use of a power optimizer, the losses must be reduce

and the device must regulate at 12V. While Figure 7 shows the

simulation of the target input and output power of the power

optimizer to prove that the device optimizes the input source

from the solar panel.

The device should also test in various load to make sure

that the reliability is achieve. The power optimizer was tested

in different inputs which are the 12V, 8V, and 17V.

Figure 8. Power Optimizer Efficiency in Various Loads

Since it is used to optimize the harness energy from the sun, the

Figure below shows the output voltage gathered of the solar

panel at 10mins interval time.

9

Figure 9. Time vs Output Voltage of the Solar Panel

The Output power is also important in gathering data. The

figure below shows the time it takes for the device to have an

output power shown below.

Figure 10. Time and Output Power Analysis

The battery is also a part of the design because the power

optimizer has the bidirectional property that allows the

simultaneously charging the battery while supplying the load.

Figure 11. Battery Charging Time based on the Weather

Condition

V. SYSTEM APPLICATION

The power optimizer is to be integrated in a solar powered

surveillance system to prolong the time of consumption of the

CCTV camera. During daytime while the battery is charging it

is also supplying the load. At night since there is not enough

sunlight, the stored energy in the battery will now be used as the

source of energy that will supply to the load. The system is

comprised of a DC-DC converter used for power management.

Resonant converter is utilized because of its soft-switching

capability. The device optimizes the energy harnessed from the

sun and it helps to reduce the switching loss and conduction loss

encountered during conversion.

VI. CONCLUSION

The developed design is an effective tool that can be used for

power management. Multiple designs can be simulated to

increase performance in handling different load requirements.

The system can be integrated into any numerous load networks

and allowed to manage different inputs and output voltages.

VII. ACKNOWLEDGMENT

The authors would like to express their gratitude to the Engr.

Shearyl Arenas for the design guidance, Technological Institute

of the Philippines – Quezon City and De La Salle University –

Manila for the research collaboration and permission on the use

of relevant hardware and software in this activity.

VIII. REFERENCES:

[1] F. Z. X. X. D. J. a. Z. Q. Junming Zhang, "A Novel ZVS DC/DC Converter for High Power Application," IEEE Transactions for Power

Electronics, 2004, pp. 420-429.

[2] B. M., "Resonant Converter Topologies," STMicroelectronics, 1999.

[3] S.-P. Yang, J.-L. Lin and S.-J. Chen, "A Novel ZCZVT Forward

Converter With Synchronous Rectification," IEEE Transactions on

Power Electronics, vol. 21, pp. 912-922, 2006.

[4] A. Skinner, "Choosing the Right Topology," Boddo's Power Systems,

2009.

[5] G. Lakkas, "MOSFET Power Losses and How they Affect Power-Supply," Analog Applications Journal, pp. 22-26, 2016.

[6] K.-H. Liu, R. Oruganti and F. C. Y. Lee, "Quasi-Resonant Converter -

Topologies and Characteristics," IEEE Transactions on Power Electronics, vol. 1, pp. 62 - 71, 1987.

[7] J. S. Glaser and M. A. D. Rooij, "Current doubler Rectifier with Current

Ripple Cancellation," 2006.

[8] S.-M. (. Chen, Tsorng-Juu and K.-R. Hu, "Design, Analysis, and

Implementation of Solar Power Optimizer for DC Distribution System," IEEE, vol. 28, no. 4, pp. 1764-1772, 2013.

[9] L. Technology, "High Efficiency, Synchronous, 4-Switch Buck-Boost

Controller," Linear Technology Corporation, California, 2005.

[10] R. M. H., Power Electronics Handbook, 2001.

10

Electrical Energy from Self-Running

Magnetic Motor

Abdul Halim Ali, Ahmad Najmuddin Che Ismail Universiti Kuala Lumpur British Malaysian Institute

Kuala Lumpur, Malaysia

ahalim@unikl.edu.my

Abstract:

The use of magnetic motor to generate electricity ever since in

the 18 century. In most cases, external resources such as hydro

and wind are needed to power the magnetic motor before an

induce electricity can be produced. In this study, a magnetic

motor is design to self-rotate it’s rotor by naturally repulsion

and the attraction of magnetic field by arranging the

magnets into Halbach array. The self-rotation magnetic

motor sometime it is known as a machine that produce

“Free Electric Energy”. Based from the results the rotor is

rotating at the constant speed that produced the torque

that lead to the development of mechanical power.

Keywords: Induction Motor, Electrical Energy,

Halbach Array, Magnetic Motor.

I. INTRODUCTION

The term “free energy” is not maybe a gas station

giving away gas however this is not the case for Nikola

Tesla where he was the first one to identify “radiant

energy” where energy harvesting the Sun. Nikola Tesla is

the key researcher in free energy theories and invented

most of the free energy devices. Tesla introduced two free

energy theories. The earlier is known as Crooke’s

radiometer and later as “cosmic-ray motor” which he

claimed to be “thousands of times more powerful” as

compare to Crooke’s radiometer. Tesla’s free energy

concept was patented in 1901 as an “Apparatus for the

Utilization of Radiant Energy.” In 1932, Tesla claimed has

successful harnessed the cosmic rays. The radiant energy

receiver stored static electricity obtained from the air and

converted it to a usable form [1, 2]. However, Tesla’s free

energy are not from the magnetic motor generator that

produce the electricity.

In this study, a free energy is created from permanent

magnet motor without utilizes resources from outside such

as burning fossil fuels namely coal, petroleum and natural

gas [3] to induced voltage. The free energy comes from the

naturally repulsion and the attraction of magnetic field that

creates the motion of electric motors. This self-running

electric motors is attached to a turbine motor shaft which

resulting an induced voltage.

The term, "Free Energy" is widely used and

often abused in the industry. Many believe no such

thing of free energy, or whatsoever machine capable to

generate energy out of nothing. In others word, there are

no such things of “perpetual motion machine” that can do

work continues indefinitely without utilizing external.

II. MAGNETIC MOTOR

The first magnetic motor was first deployed in 1880 is

a direct current (DC) magnetic motor when direct current

was the only source of power, until Nikola Tesla invented

the alternative current (AC) magnetic motor in 1889 where

in 1886 the starting era of AC power system in the world.

The induction energy from AC magnetic motors need

external resources for operations such as hydro dams to

and windmills. With the exception of solar

power, 95% of the induction of electricity in the

world comes from electromagnet -based power

generating systems by setting magnets into

motion while wrapping windings of magnet wire

around the magnet to induce electricity. Since

than the research development of an AC magnetic

motor growth has never stop.

The configuration of the magnets in the self -

running magnetic motor in this study using

Halbach array. The simplest Halbach array

configuration as shown in figure 1 is creating

strong magnetic field at one side while cancelling

the field to near zero on the others side of the

array. The magnetic field lines of the Halbach

array is shown in figure 2.

Figure 1: Simple Halbach array configuration

Strongest side of magnetic field

Canceled side of magnetic field

11

Figure 2: The magnetic field lines of Halbach array [4]

The main advantages of using Halbach array where the

magnetic field strength produced is very strong and

increases the efficiency of the magnetic circuit as compare

with others arrays configurations. However, the main

drawback of such configuration it’s difficult to assemble

and the magnets are arranged in a direct or quasi-direct

repelling condition that will act to demagnetize their

neighboring magnets. The Halbach array configuration

major applications of the one-sided flux distribution

ranging from the simple refrigerator magnet to much

complicated application deployed in the Maglev train

(magnetic levitation).

The general description of the Halbach array

configuration magnetization pattern was given by [5], a

simple superposition of two trigonometric functions as

shown in equations 1 & 2

where λ denotes the wavelength and the magnetization

amplitude.

III. SELF-RUNNING MAGNETIC MOTOR DESIGN

The self-running magnetic motor is designed with 3 layers

as shown in figure 3. The basis of the design is based on

[6]. The most inner magnets consists of 10 magnets, the

middle magnets is made of 14 magnets and the outer

magnets is comprises of 21 magnets. The magnets field

arrangements follow Halbach array [7]. The middle and

the outer layers are the stator whereas the most-inner layer

act as rotor. The inner radius of the magnets is at 4.1cm,

the middle magnets radius at 6.4cm and outer magnets

radius at 1.7cm with an air-gap of 0.3cm between the

magnets. The whole radius of the design is at 12.5cm. The

magnets material use “neodymium (NdFeB) n52” is the

strongest permanent magnet commercially available in the

market. The property of the NdFeB n52 magnet is shown

in Table 1 and it is made from an alloy of neodymium, iron

and boron.

Table 1: Property of NdFeB n52 magnet Remanance (Br) Coersive

Force Hcb (Hc)

Intrensic

Coersive

Force Hcj (Hj)

Maximum

Energy Product

(BH) Max

mT G K A/M Oe K A/M Oe KJ/m³ MGOe

1430 14300 796 10000 876 11000 398 50

Figure 3: Self-running magnetic motor with

Halback magnetic field directions

Figure 4 shows the 3D design of the self-running

magnetic motor

Figure 4: The 3D design of self-running

magnetic motor

IV. SIMULATION RESULTS

The self-running magnetic motor design is tested using

Finite Elements simulations tool. The Finite Elements

FEMM4.2 is an open source magnetic motor that provide

wide range of possibilities to simulate the design. Figure 5

shows the magnetic field strength of the self-running

magnetic motor obtained from FEMM4.2

Figure 5: The magnetic field strength

12

Figure 6 shows the simulation results of relative

centrifugal force (RFC) produces by the self-running

magnetic motor. It is notice from the graph for 360 turn it of the self-running magnetic motor produces two cycles response. This is due that the rotor have ten magnets where the arrangement is set into two sets of Halbach array. Each set of Halbach array results in one complete cycle.

Figure 6: RFC waveform

To confirm that the rotor is rotating at a constant speed 10

cycles of 360 were simulated and the results are shown in

in Figure 7 and 8. Constant responses were recorded in

figure 7 showing that the rotor is rotating at a constant

speed.

Figure 7: RCF responses of 10 cycles

Figure 8 shows the harmonics of the 10 cycles. The

harmonics response of the 10 cycles shows the same as of

figure 6. This shows the design of the self-running

magnetic motor the rotor is rotating at the same frequency.

Torque is another important parameter that can be

measured from the simulation. Figure 9, shows the torque

response as expected it’s produced two cycles from 360

turn from the self-running magnetic motor as can be seen in figure 6 of RCF.

Figure 8: RCF Harmonics of the 10 cycles.

Figure 9: Torque response form simulation

From equation (3) the revolution per minute (rpm) of

the rotor in the self-running magnetic motor can be

calculated. The rpm is needed as it is part of the equation

(4) to find the mechanical power.

where

RCF = relative centrifugal force,

r = centrifugal radius in mm

From (3) the rpm can be plotted as shown in figure 10.

13

Figure 10: Revolution per minute (rpm) response

Once torque is obtained the mechanical power can be

calculated by using the equation shown in (4):

The main objective of this study and the most important is

the capability of the self-running magntic motor to induce

electricity. In normal cases the efficiency of the generator

are working around 90% to produce electrical power.

Hence, the electrical power can be derived from

mechanical power as shown in equation (5). The

comparison output of the mechanical power versus

electrical power are as shown in figure 11.

Electrical Power = 0.9 x Mechanical Power (5)

Figure 11: Mechanical power from self-running

magnetic motor

V. CONCLUSION

From the study, it can be concluded it is possible to

induce electricity from self-running magnetic motor.

However, this primarily finding will needs further

investigation before a prototype can be developed.

REFERENCES

[1] https://www.greenoptimistic.com/tesla-free-

energy/#.WgEzRVNx11s (7Nov2017)

[2] https://www.nuenergy.org/nikola-tesla-radiant-energy-system/

(7Nov2017)

[3] M. Casis, et al., "Free-Energy Generator," Pulsar, vol. 1, 2013

[4] https://www.duramag.com/techtalk/halbach-arrays/how-are-

halbach-arrays-designed/ (16Nov2017)

[5] J. Mallinson, “One-sided fluxes – A magnetic curiosity?” IEEE Transactions on Magnetics, vol. 9, no. 4, pp. 678–682, Dec. 1973

[6] Amel Ridha, “Design and Simulation of Free Energy Permanent

Magnet Motor (FEPMM)”, European Journal of Scientific

Research, vol. 138 No 3 March 2016, pp.123-132

[7] C.G.C. Neves, A.F.F. Filho, “Analysis a Magnetic Gear Integrated

Halbach PM Generator”, XVII International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic

Engineering (ISEF2015), Valencia, Spain, 10-12 September 2015.

14

A Review on Voltage Wave Reflection in

Transmission Lines

Awadh.Al-Kalbani Suhar College of Applied Sciences

awadhk.soh@cas.edu.om

Abstract—The paper starts with the traditional literature

theory on Telegrapher equations solution and wave propagation

and reflection along the transmission line. Few books were

referenced on this theory. In the discussion section, the paper lists

how the reflection theory is physically wrong. In the end of the

discussion, the paper argues, the wave in transmission line can be

decomposed in different ways and is best described as a signal

being modulated by the transmission line impedance.

Transmission line problems can be solved with physically correct

theory and basic circuit theory laws.

Index Terms— Reflection coefficient; Telegrapher equations;

Transmission lines; Voltage reflection.

I. INTRODUCTION

Books explain the wave propagation in TEM transmission

lines (TL), e.g. the coaxial cable, as a voltage (or current)

wave propagating and reflecting along the TL. This paper is to

lay the option of using physically correct and less confusing

theory in solving TL problems. Correct analysis of a

transmission line problem, can lead to a new solutions.

II. LITERATURE REVIEW

Figure 1: Lumped-element circuit model

A. TEM Transmission line model

A high frequency transmission line can be modeled by the

“lumped-element circuit” model as shown in Figure 1. The

Transmission line is orienting along the z-direction, Which is

subdivided into differential sections each of length Δz.

Where:

R': The combined resistance of both conductors per

unit length, in Ω/m.

L': The combined inductance of both conductors per

unit length, in H/m.

G’: The conductance of the insulation medium

between the two conductors per unit length, in S/m, and

C’: The capacitance of the two conductors per unit

length, in F/m.

B. Relationship between current and voltage in a

transmission line

Referring to Figure 1, and analyzing one section as shown in

Figure 2:

Figure 2: A section model

The solution of the relationship between the current and the

voltage as Δz→0 , is the Telegrapher equatios:

− 𝜕𝑣(𝑧, 𝑡)

𝜕𝑧= 𝑅′𝑖(𝑧, 𝑡) + 𝐿′

𝜕𝑖(𝑧, 𝑡)

𝜕𝑡

(1)

and :

−𝜕𝑖(𝑧, 𝑡)

𝜕𝑧= 𝐺′𝑣(𝑧, 𝑡) + 𝐶′

𝜕𝑣(𝑧, 𝑡)

𝜕𝑡

(2)

which is in phasor form:

15

−𝑑(𝑧)

𝑑𝑧= (𝑅′ + 𝑗𝜔𝐿′)𝐼(𝑧),

−𝑑𝐼(𝑧)

𝑑𝑧= (𝐺′ + 𝑗𝜔𝐶′)(𝑧).

(3a)

(3b)

the solution to these differential equations is:

(𝑧) = 𝑉0+𝑒−𝛾𝑧 + 𝑉0

−𝑒𝛾𝑧

𝐼(𝑧) = 𝐼0+𝑒−𝛾𝑧 + 𝐼0

−𝑒𝛾𝑧

(4a)

(4b)

where: Vo+

, Io+

, Vo- , Io

- , are constants but are called wave

amplitudes in the traditional TL theory, and:

𝛾 = √(𝑅′ + 𝑗𝜔𝐿′)(𝐺′ + 𝑗𝜔𝐶′) (5)

This is a constant and is called the complex propagation

constant.

γ can be split into real and imaginary parts:

γ=α+jβ (6)

C. Relationship between the current I (z) and the voltage

V (z)

Using equations 3a, and 4a, the following can be produced:

𝐼(𝑧) =𝛾

𝑅′ + 𝑗𝜔𝐿′[𝑉0+𝑒−𝛾𝑧 − 𝑉0

−𝑒𝛾𝑧] (7)

or rearranging:

𝐼(𝑧) =𝑉0+

𝑍0𝑒−𝛾𝑧 −

𝑉0−

𝑍0𝑒𝛾𝑧

(8)

where:

𝑍0 =𝑅′ + 𝑗𝜔𝐿′

𝛾= √

𝑅′ + 𝑗𝜔𝐿′

𝐺′ + 𝑗𝜔𝐶′ (𝛺)

(9)

D. Transmission line circuit

A common Transmission line configuration is shown in

figure 3.

Figure 3: Common transmission line circuit

Notice z=0 is chosen where the load is. Then d=-z, can be

used in the TL voltage and current equations.

A common assumption in TL circuits is α=0, then γ

becomes: γ=jβ

Thus the TL voltage and current equations would become:

(𝑧) = 𝑉0+𝑒−𝛽𝑧 + 𝑉0

−𝑒𝛽𝑧 ,

𝐼(𝑧) =𝑉0+

𝑍0𝑒−𝛽𝑧 −

𝑉0−

𝑍0𝑒𝛽𝑧

(10a)

(10b)

According to the traditional text:

“Vo+

, Io+

, Vo- , Io

- are unknown constants which can be

found in the context of the complete circuit.

𝑒−𝑗𝛽𝑧 is associated with a wave traveling in the positive z

direction, from the source (sending end) to the load (receiving

end). Accordingly, we will refer to it as the incident wave, with

Vo+

as its voltage amplitude. Similarly, the term containing

𝑒𝑗𝛽𝑧 represents a reflected wave with voltage amplitude Vo- ,

traveling along the negative z-direction, from the load to the

source.“ [1]

The same explanation from the next book:

“where Vo+

, Io+

, Vo- , and Io

- are wave amplitudes; the +

and — signs, respectively, denote

wave traveling along +z and –z directions, as is also indicated

by the arrows.”[2]

And this is the same explanation from another book:

“In considering the voltage function that will satisfy (13), it

is most expedient to simply state the solution, and then show

that it is correct. The solution of (13) is of the form:

V(z, t) = f1 (t – z/ ν) + f2 (t + z/ ν ) = V + + V –

where ν, the wave velocity, is a constant. The expressions (t

± z/ν) are the arguments of functions f1 and f2. The identities

of the functions themselves are not critical to the solution of

(13). Therefore, f1 and f2 can be any function. The arguments

of f1 and f2 indicate, respectively, travel of the functions in the

forward and backward z directions. We assign the symbols V

+ and V − to identify the forward and backward voltage wave

components. To understand the behavior, consider for

example the value of f1 (whatever this might be) at the zero

value of its argument, occurring when z = t = 0. Now, as time

increases to positive values (as it must), and if we are to keep

track of f1(0), then the value of z must also increase to keep

the argument (t − z/ν) equal to zero. The function f1 therefore

16

moves (or propagates) in the positive z direction. Using

similar reasoning, the function f2 will propagate in the

negative z direction, as z in the argument (t + z/ν) must

decrease to offset the increase in t. Therefore we associate the

argument (t − z/ν) with forward z propagation, and the

argument (t + z/ν) with backward z travel. This behavior

occurs irrespective of what f1 and f2 are. As is evident in the

argument forms, the propagation velocity is ν in both cases.”

[3]

The following things follow the above assumptions:

- The reflection coefficient at the load, which is used to

measure the energy transfer to the load:

Γ= Vo-/ Vo

+ (11)

best energy transfer to the load happens when Γ=0.

- The characteristic impedance, which is said to give

the relationship between the voltages and the

currents. 𝑉0+

𝐼0+ = 𝑍0 =

−𝑉0−

𝐼0− (Ω) (12)

E. Another term for the relationship between the current

I (z) and the voltage V (z)

𝑍(𝑧) =(𝑧)

𝐼(𝑧)=𝑉0+𝑒−𝛾𝑧 + 𝑉0

−𝑒𝛾𝑧

𝐼0+𝑒−𝛾𝑧 + 𝐼0

−𝑒𝛾𝑧

= 𝑍0(

𝑉𝐿𝐼𝐿+ 𝑍0𝑡𝑎𝑛ℎ[𝛾(𝑙 − 𝑧)]

𝑍0 +𝑉𝐿𝐼𝐿𝑡𝑎𝑛ℎ[𝛾(𝑙 − 𝑧)]

)

(13)

III. OBJECTIVES

- To correct the traditional theory of voltage reflection in

transmission lines.

- Provide a correct explanation to the voltage wave on the

transmission line which may be followed by a corrected

approach in solving TL problems, e.g. matching.

IV. DISCUSSION

A. Reflecting wave don’t occur for the following reasons:

i. Equations 10a and 10b happen to be a

mathematical solution to differential equations.

Both Vo+ and Vo- are obtained from V(0) and

V’(0) (when getting the particular solution to a

differential equation) and not from a V(z) at the

reflection point. Therefore, V(z) can be

decomposed into to sinusoidal waves one a

function of z and the other a function of –z. It

can also be decomposed into different ways not a

function of (-z). Therefore, there is no reason to

extend the mathematical solution into 𝑉0− being a

result of some sort of a physical reflection.

ii. It breaks circuit theory law (i.e. what’s normally

called Ohms law for phasors): 𝑉(𝑧)

𝐼(𝑧) = Z(z) , should always be the case to stasify circuit

theory laws.

However:

𝑉0+

𝐼0+ = 𝑍0 =

−𝑉0−

𝐼0−

does not satisfy circuit theory laws. 𝑍0is generally not the

impedance of the TL.

iii. The Electric Field and the Magnetic Field do not

travel along the TL, that’s why the TL is referred

to as TEM line. e.g. in the coaxial cable case, the

Electric Field travels from the center conductor

to the outer conductor across the cable. Thus the

current following in a TL should not be confused

with the Electromagnetic (EM) wave

propagation. i.e. The EM waves do not travel

from the source to the load. The current travels

from the source to the load.

iv. The theory of the reflecting wave is not

repetitive, units have to be made up and require a

lot of fix’s for different cases. e.g.:

o The reflection coefficient at the load is not

the same throughout the line. Γ(z) depends

on the distance on the line! How this can be

comprehended physically?

o The relationship between the incident

voltage amplitude Vo+

and incident current

amplitude Io+ is 𝑍0 as shown in equation

(12), but the relationship between the

reflected voltage amplitude and the reflected

current amplitude is Io- is –𝑍0 (i.e. with a

negative sign).

o 𝑍0 in equation (9) is assigned to have a unit

of ohms, but it doesn’t really calculate to a

unit of ohms. R’ unit is ohms per meter.

B. An alternative solution to the Telegrapher equations

By substituting equation 3a and 3b into each other:

𝑑2(𝑧)

𝑑𝑧2− 𝛾2(𝑧) = 0

𝑑2𝐼(𝑧)

𝑑𝑧2− 𝛾2𝐼(𝑧) = 0

(14a)

(14b)

For a lossless TL, γ=jβ, therefore equation (14a) becomes:

𝑑2(𝑧)

𝑑𝑧2+ 𝛽2(𝑧) = 0

(15)

Applying Laplace transform to solve the equation:

𝑠2𝑉(𝑠) − 𝑠(𝑧 = 0) − ′(𝑧 = 0) + 𝛽2𝑉(𝑠) = 0

Rearranging:

17

𝑉(𝑠)[𝑠2 + 𝛽2] = 𝑠(𝑧 = 0) + 𝑉′(𝑧 = 0) Therefore:

𝑉(𝑠) = 𝑠(𝑧 = 0) + 𝑉′(𝑧 = 0)

[𝑠2 + 𝛽2]

= 𝑠(𝑧 = 0)

[𝑠2 + 𝛽2]+ 𝑉′(𝑧 = 0)

[𝑠2 + 𝛽2]

Now taking inverse Laplace transform:

(𝑧) = (𝑧 = 0) cos𝛽𝑧 +𝑉′(𝑧 = 0)

𝛽sin 𝛽𝑧

Where (𝑧 = 0) 𝑎𝑛𝑑 𝑉′(𝑧 = 0) are generally

complex values. (𝑧) in equation (16) is readily

decomposed into two waves one is (𝑧 = 0) cos𝛽𝑧

And 𝑉′(𝑧=0)

𝛽sin 𝛽𝑧. Now writing it in time domain:

𝑣(𝑧, 𝑡) = |(0)| cos(𝛽𝑧) 𝑐𝑜𝑠 (𝜔𝑡 + ∠(0)) +

|𝑉′(0)|

𝛽𝑠𝑖𝑛(𝛽𝑧)𝑐𝑜𝑠 (𝜔𝑡 + ∠𝑉′(0))

Equation(17), shows that the transmitted wave

(analogous to carrier) would be modulated by the TL

(or (𝑧)) , instead of being reflected.

To find |(𝑧)| which is detectable by SWR meter, lets

first rewrite (𝑧) 𝑎𝑠:

(𝑧) = (𝑎 + 𝑗𝑏) cos 𝛽𝑧 +(𝑐 + 𝑗𝑑)

𝛽sin 𝛽𝑧

Where, a+jb=(𝑧 = 0) and c+jd= 𝑉′(𝑧 = 0):

Then:

(𝑧) = 𝑎 cos𝛽𝑧 +𝑐

𝛽sin 𝛽𝑧

+ 𝑗 [(𝑏 𝑐𝑜𝑠 𝛽𝑧 +𝑑

𝛽𝑠𝑖𝑛 𝛽𝑧]

Then using Pythagoras law for magnitude and basic

trigonometry for the angel:

(𝑧) =

√[𝑎 cos 𝛽𝑧 +𝑐

𝛽sin𝛽𝑧]

2

+ [(𝑏 𝑐𝑜𝑠 𝛽𝑧 +𝑑

𝛽𝑠𝑖𝑛 𝛽𝑧]

2

tan−1𝑏 𝑐𝑜𝑠 𝛽𝑧 +

𝑑𝛽𝑠𝑖𝑛 𝛽𝑧

𝑎 𝑐𝑜𝑠 𝛽𝑧 +𝑐𝛽𝑠𝑖𝑛𝛽𝑧

Then, |(𝑧)| =

√[𝑎 cos 𝛽𝑧 +𝑐

𝛽sin𝛽𝑧]

2

+ [(𝑏 𝑐𝑜𝑠 𝛽𝑧 +𝑑

𝛽𝑠𝑖𝑛 𝛽𝑧]

2

(16)

(17)

(18)

=

√ [𝑎2 + 𝑏2

2−𝑐2 + 𝑑2

2𝛽2] cos(2𝛽𝑧)

+ [𝑏𝑑 + 𝑎𝑐

𝛽] sin(2𝛽𝑧)

+ [𝑎2 + 𝑏2

2+𝑐2 + 𝑑2

2𝛽2]

If the load is matched |(𝑧)| should become a

straight line against z (as known in TL). So matching

conditions are:

[𝑎2 + 𝑏2

2−𝑐2 + 𝑑2

2𝛽2] = 0 𝑎𝑛𝑑 [

𝑏𝑑 + 𝑎𝑐

𝛽] = 0 𝑜𝑟 𝑏𝑑

= −𝑎𝑐

But 𝑎2 + 𝑏2 = |𝑉 (0)| 2and 𝑐2 + 𝑑2 = |𝑉′(0)|2

Thus the matching conditions are:

|(0)| 2 =|𝑉′(0)|2

𝛽2 𝑜𝑟 |(0)| =

|𝑉′(0)|

𝛽𝑎𝑛𝑑

𝑏

𝑎= −

𝑐

𝑑 𝑦𝑖𝑒𝑙𝑑𝑠→ ∡(0) = ∡[′(0)]

Combining the two conditions:

(0) =′(0)

𝛽

Which happens if the load impedance matches with

Thevenin impedance of the circuit. This statement is

alternative to the traditional theory of reflection

coefficient Γ=0.

V. CONCLUSION

- The voltage reflection theory is not correct though it

works (with few fixes) to solve TL problems.

- The voltage reflection theory is not essential to solve TL

problems. They can be solved using correct

understanding of standing wave and basic circuit theory

analysis.

- A complete corrected theory and methods can be

developed to update the traditional methods for solving

TL problems. e.g. more work can be done to write the

relations of ZL, Zo, (0)𝑎𝑛𝑑 𝑉 ′(0).

VI. REFERENCES

[1] Fawwaz T. Ulaby, Eric Michielssen. Fundamentals of Applied

Electromagnetics. Sixth. London : Pearson, 2014. pp. 54-78.

[2] N.O.Sadiku, Mattew. Elements of Electromagnetics. s.l. : Oxford, 2011. p. 515.

[3] William H. Hayt, J. John A.Buck. Engineering Electromagnetics. s.l. :

McGraw Hill, 2006. p. 307.

18

Development of Dual Axis Solar Cells Tracking

Prototype Based on PVC Foam Material

H. Sharabaty, O. Khazraji Department of Electrical & Electronics Engineering, University of Turkish Aeronautical Association, Ankara, Turkey

sharabaty@ieee.org

Abstract—with a view to evolving additional solar energy and to

raise the efficiency of the solar photovoltaic panels, tracking

systems are used to follow the sun position and to let the solar

photovoltaic panels head for the sun as long as possible. This paper

proposes to use PVC foam material instead of the other materials

such as Iron and Plastic in order to develop a dual axis solar panel

tracking prototype based on AVR microcontrollers. Compared to

other materials, PVC foam withstands more temperatures and can

reduce the design weight and power consumption. In addition, this

work proposes to discretize the tracking operation of sun position

by switching DC relay, and to study the effect of the consumed

energy, by the control circuit and motors, on the total generated

energy of the system, and then to determine the optimal DC relay

timing period. Finally, this work discusses the advantages of

connecting solar cells in series regarding the solar panel output

voltage. The experimental work shows that compared to the static

solar system, the proposed dual axis solar tracking prototype is

more efficient for absorbing higher sunlight by increasing the

average power by 34%. Moreover, the measurements proved that

the optimal interval for discretize tracking system is 20 minutes

that gives the maximum achieved efficiency of the prototype, i.e.

34%. Compared to the continuous tracking system, the optimal

tracking interval saves 89.45% of the consumed energy by the

control circuit.

Index Terms— AVR microcontrollers; Discrete sun tracking;

Dual axis solar tracker; Solar cells; PVC foam material.

I. INTRODUCTION

Solar energy is very effective and efficient to produce

electricity especially in countries where the warm climate is

mostly dominant [1]. The problem here is that the solar

photovoltaic (PV) has low efficiency in producing maximum

output power which is derived from sunlight [2]. To fix this

problem up, several works have been achieved to increase the

efficiency of the output power by using the solar tracking

system that maintains the solar PV panels perpendicular to sun

radiation [2]. This can increase the efficiency of energy

production up to 35% based on annual estimation [3]. The first

proposed solar tracking systems were single axis tracker [4, 5,

6]. Later on, the most efficient algorithm to control the dual-

axis solar tracker which could rotate in direction of azimuth and

elevation were simulated and implemented [7, 8, 9, 10]. The

previous studies show that two types of solar panel tracking

prototypes were proposed:

The first one contains big solar panels and can be used for

energy-generating purposes because the total average of the

generated energy is higher than the total energy of the

consumption [11, 12, 13].

The second type was dedicated for research purposes in labs

and universities and was contains small solar panels. The main

problem here is that the total energy of the consumption of these

small prototypes is higher than the total average of the

generated energy [6, 8, 9].

II. METHODOLOGY AND PROPOSED DESIGN

This part focuses on the design and implementation of the

proposed dual axis solar panel tracker prototype. The

mechanical parts of the proposed system are drawn by

AutoCAD 2017 program because it is considered as the main

part of utilizing the PVC foam in the Computer Numerical

Control machine (CNC). By using the AutoCAD to draw the

required pieces, the commands and the drawings sent to the

PVC foam cutting machine (CNC) in order to cut the required

pieces. Later on, we put Length = 1 meter & Thickness = 1cm

from the PVC foam material under the CNC machine and turn

on the cutting machine. Directly, the CNC started to cut

according to the design, drawings, and scales. The aim of the

proposed dual axis solar panel tracking system is to keep the

solar panel facing toward the sun all the day. Therefore, we

have to track the position of the high intensity of the sunlight

by using the LDRs. The proposed design depends on the

obtained value of the voltage difference between the four LDRs

which are located in a shape of a square on the upper section of

the design. Automatically, the panel will rotate according to the

obtained value. As shown below in figure 1, the proposed dual

axis solar panel tracking system consists of the sensing unit, the

microcontroller unit, and the two servo motors (rotation unit).

Figure 1: Block diagram of the proposed prototype

The components of the proposed solar panel tracking system

are very sensitive. Therefore, it requires precision and

concentration during the work. These components are

19

electrical, electronic and mechanical. The proposed solar panel

tracking system consists of two main circuits. The purpose of

the first circuit is to sense the solar radiation by using LDRs, to

control the Arduino Uno which is the brain of the design and to

control the two servo motors (vertical and horizontal). The

purpose of the second circuit which is the solar panel circuit is

to convert the solar energy into electrical energy and to supply

the electrical energy into the load.

A. Arduino Uno board is the microcontroller and the brain of

our design. It receives analog signals from the LDRs by the

analog pins and sends pulse width modulation signals (PWM)

by the PWM digital pins to the two servo motors (horizontal

and vertical). Therefore, regarding the voltage of this

microcontroller unit, the Input voltage is 9V.

B. Servo motor (MG 946R) is the mechanical component of

the proposed design. It has tough metal gears. We preferred this

type of servo motors because it has high quality and high torque

during the work of the solar panel tracking system. It has three

main wires, the orange wire is for the pulse width modulation

signal (PWM), the red wire is for the operating voltage (V+)

and the last wire is for the ground. There are two servo motors

which are the horizontal and the vertical servo motors. The

horizontal servo motor controls the horizontal angle of the

design (from east to west) while the vertical servo motor

controls the vertical angle of the design (from south to north).

Eventually, the operating voltage for the two servo motors is

7.2V.

C. The light dependent resistor (LDR) is the sensing part of

the proposed design. This part can work as a light sensor to

detect the absence and the presence of light. We chose them

because they can cost a low price, as well as it has high

sensitivity and simple structure. We put four LDRs in the upper

section of the design in a shape of a square. Directly as the

(LDRs) sensing the light, they will give analog signals to the

microcontroller. Moreover, the input voltage to the LDRs is 5V.

The fixed resistors which are connected in series with the LDRs

to form a potential divider circuit. The center point of the

potential divider is fed to the analog pins of the Arduino board.

In practical, we selected four fixed resistances in the proposed

design and the value of each resistance is (360Ω).

D. Voltage regulation (LM2596) is a DC to DC step down

regulation. We chose it because it is adjustable and ideal for the

proposed design and we needed to step down the input voltage

from 9V (adaptor) to 7.2V (servo motor voltage). We regulated

the voltage from the adjustable part by using the screw-driver

and checked the voltage by using the AVO meter.

E. The thermometer is used to measure the temperature of the

solar panel. The unit of this part is Celsius degree. It is very

accurate to the exact temperature. The input voltage for this part

is 5V.

F. We chose a resistance (10W 300ΩJ) as a load which is

connected with the solar cells (series or parallel case). The load

voltage and the current depend on the solar energy absorbed by

the solar panel. Eventually, we measured the output voltage and

the current on both ends of this load by using the AVO meter.

G. 10 solar cells (6V 0.1W) in two cases (parallel and series

connection) cost low prices and give high efficiency in

absorbing the solar energy and converting it into electrical

energy. Even though the output power of the solar panel is quite

small, but the solar panel is enough to show that the sunlight

energy can be grabbed as much as possible because the solar

panel is moving in response to the direction of sunlight that

sensed by LDRs.

III. THE WORKING PRINCIPLE

The working principle of the proposed prototype is when the

sunlight falls on the LDRs, the microcontroller will sense the

variation of light by the analog pins. We have 3 cases:

A. Case 1

When the sun is located on the right or left or up or down the

four LDRs, the voltage value will increase in the analog pins

which are connected on the LDRs toward the sun and will

decrease on the LDRs opposite to the sun. For example, if the

sun is located on the right side of the four LDRs, the voltage

value will increase in the right analog pins and will decrease in

the left analog pins. Then, the microcontroller will calculate the

average of the increasing voltage between the right up LDR and

the right down LDR. Also, it will calculate the average of the

decreasing voltage between the left up LDR and left down

LDR. By applying the subtraction operation on the two

resulting averages, the resulting value from the operation will

take these results as commands to move the horizontal motor to

the right direction and to equalize the voltages of the analog

pins by equalizing the intensity of the sunlight on the LDRs.

Moreover, for the other directions, we can apply the same

operation in order to show the aimed results.

B. Case 2

When the sun is located on the right up or left up or right down

or left down the four LDRs i.e. the effect of the sun will be in

two directions (will not be in one direction). For example, if the

sun is on the right up of the four LDRs, the LDR which is

located on the right upside will be towards the sun and the

voltage of this analog pin will increase. Contrastingly,

regarding the sensor which is located on the opposite side to the

sun (the left down sensor), the voltage of the connected analog

pin will be lower than the other pins. Thus, when the

microcontroller does the calculation, the right analog pins

voltages will be increased and the upper analog pins voltages

will also be increased. Moreover, the vertical servo motor will

move up and the horizontal servo motor will move to the right

till the voltages of the analog pins will be equalized. This

process can be applied to the other directions to show the aimed

results.

20

C. Case 3

In the case of darkness or the same amount of the falling solar

rays on the four LDRs, the voltages of the four analog pins will

be equal and the microcontroller will command the 2 servo

motors to stay in the same position (no motion).

We programmed the Arduino Uno board by using the Arduino

C language to write the codes and command the Arduino C

program (Personal Computer) to send these codes to the

microcontroller board by using external cable. The Flowchart

of the tracking operation is shown in Figure 2.

Figure 2: Flowchart of the tracking operation

The proposed dual axis solar panel tracking system, which has

been practically achieved, is shown in Figure (3).

Figure 3: The proposed prototype

IV. RESULTS AND DISCUSSIONS

In this part, we summarize the acquired results during our work.

We start by comparing our prototype with another prototype

developed by the department of electrical and electronic

engineering at Baghdad University. This prototype was built

for research purposes in Renewable energy laboratory and was

made of iron, plastic and cements materials. Then, we will

compare between the energy resulted from the static solar cells

system and from the dual axis solar tracker by using ten solar

cells with the same output power. We will discuss both cases:

series and parallel connection. After that, we will show the

results of the tracking and static systems of the parallel case and

calculate the average power. Then, we will display the energy

values of the tracking and static prototypes of the series case.

The tracking system will be track the sun by switching the DC

relay for an interval of time (5 mins, 10 mins, 15 mins, 20 mins,

30 mins, 40 mins, 50 mins, 55 mins, 1 hr, 2 hrs, 3 hrs, 4 hrs and

6 hrs) for a duration of 12 hrs while the static prototype will

remain fixed toward the sun at 90 degrees angle all the day. We

will determine the energy consumption and generation of our

prototype for all cases and through them, we will calculate the

efficiency. The measurements have been done in Baghdad

during the period from 10 to 31 August 2016, and the results

were registered according to specific intervals of time from 6

am to 6 pm because sunrise in that period was between 5:21 and

5:35 am, whereas the sunset was between 18:53 and 18:28 pm.

A. Weight of Our Proposed Design

We compared the weight of our prototype with a prototype built

at the University of Baghdad in the laboratory of electrical and

electronic engineering for research experiments of student's

research with the same specifications but made of iron, plastic

and cement as shown in the figure 4 and compare the weight

values of the prototypes illustrated in table 1.

Table 1

Comparison with reference prototype

THK Prototype UOB Prototype

Weight of The Prototype

2.5 Kg

4 kg

Material

PVC Iron+plastic+Cement

Figure 4: The reference prototype and our proposed prototype

Therefore, the proposed design has less weight than the other

design.

B. Parallel Solar Cells Connection

We will connect ten solar cells in parallel to the load to calculate

the average power value as shown in figure 5.

This figure demonstrates the data of power which are collected

by static and rotating solar panels for the First day. The static

solar panel data displays that the maximum power is 0.2045 W.

21

For the meantime, the rotating solar panel data displays that the

highest power is 0.1939 W. From figure 4, the power values

produced by the rotating panel are approximately equal during

the time of testing. But, for the static panel, it can be seen that

the solar intensity increases from 06:00 to 07:00 until 09:00 to

10:00. Then, the solar intensity starts to decrease smoothly until

at 17:00 to 18:00.

Figure 5: Interpretation data of power of solar panel 0.12 W

Figure 4 shows an increase in the total average power which is

collected from the tracker solar panel in comparison to the total

average power which is collected from the static solar panel.

C. Series Solar Cells Connection

We will connect ten solar cells in series case to the load to

calculate the average energy value by switching the DC relay

for multiple intervals of time (5 mins, 10 mins, 20 mins, 30

mins, 40 mins, 50 mins, 55 mins, 1 hr, 2 hrs, 3 hrs, 4 hrs, and 6

hrs) for a duration of 12 hours.

The first case is switching the DC relay by using an interval of

5 minutes for 12 hours

Figure 6: Rotating vs. static system for switching interval of 5mins

The results illustrated in figure 6 shows the obtained energy

from the static and the tracker panels. By using the tracking

system, the maximum energy was 237.4682 J could be reached

from 10:55 to 11:05. Contrastively, without using the solar

tracking system (static system), the maximum energy reached

from 12:00 to 12:05 is 178.47 J. Also, the obtained energy of

the tracker panel at any other time period is more than the

obtained energy of the static panel at the same period. Figure 6

also shows an increase in the total average energy which is

collected from the tracker solar panel in comparison with the

total average energy collected from the static solar panel.

Calculating the area under the envelope of the generated energy

curve for the solar tracking system gives us the total average

energy (Et) = 25871.50 J/Day. As a result, the total average

energy obtained from the solar tracking system that follows the

sun by an interval of 5 minutes for 12 hours is equal to 25871.50

– 10760.94 = 15110.56 J/day. On the other hand, the total

average of the generated energy from the solar static system

(Es) is equal to 11322.85 J/Day. So, we can define the

efficiency of our prototype by:

The efficiency = ((Et-Es)/Es) * 100% ………… (1)

Where

Et: The total average generated energy by the tracking system.

Es: The total average generated energy by the static system.

Using the equation 1, the efficiency of our system by using

switching interval of 5 minutes is 33.45%. These calculations

can be applied to the other cases to show the aimed results.

D. Energy Consumption of the Prototype

Here, we will consider that the continuous sun following system

will switch the DC relay using an interval of 1 second. The

Energy consumption of the control circuit is 10458.72 J and the

energy needed to move the motors for 1 second is 89424 J as

well as the motor needs energy to return to the start after the

demise of the sun by 4.14 J. Therefore, the total energy

consumption in the case of switching DC relay using an interval

of 1 second for 12 hours is 99886.86 J and Figure 7 explains the

total energy consumption for the other different switching

intervals.

00.05

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050

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10300

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rsE

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Figure 7: Energy consumption Curve

The highest total energy consumption appears in the case of

switching the DC relay by using an interval of 5 minutes for 12

hours while the less total energy consumption appears in the

case of switching the DC relay by using an interval of 6 hours

as shown in figure 7.

E. The Generated Energy Gain

We will consider that the difference between the total average

of the generated energy and the total consumed energy as

produced energy gain.

Figure 8: Generated energy gain curve

The highest generated energy gain appears in the case of

switching the DC relay by using an interval of 20 minutes for

12 hours while the less generated energy gain appears in the

case of switching the DC relay by using an interval of 6 hours

as shown in figure 8.

F. Efficiency of The Proposed Prototype

It is the ratio of the difference between the total average of the

generated energy of the tracking prototype and the total average

of the generated energy of the static prototype to the total

average generated energy of the static prototype.

The highest efficiency appears in the case of switching the DC

relay by using an interval of 20 minutes for 12 hours by 34% as

shown in figure 9.

Figure 9: Efficiency curve of the proposed prototype

V. CONCLUSIONS AND RECOMMENDATIONS

In this work, we designed and implemented a dual axis solar

tracker prototype to track the movement of the sun as the sun

rises from the east and sets into the west during the day. The

prototype has been designed by using AutoCAD 2017. The

mechanical parts have been cut by using a Computer Numerical

Control (CNC). The control circuit was achieved by using the

AVR microcontroller and it has been practically tested. We also

proposed to use PVC foam material in order to reduce the

weight of the prototype and decrease the energy consumption.

Likewise, PVC foam material can withstand the high

temperatures of Iraq weather that can arrive at 56. For

decreasing the energy consumption and increasing the

efficiency of the prototype, we propose the discretizing for the

tracking operation of sun position by using a switching DC

relay. The optimal switching interval was 20 minutes that

increased the efficiency of our prototype to 34%. This optimal

tracking period saved 89.45% of the requested energy for the

control circuit in comparison with the continuous tracking

system. Our proposed dual axis solar tracking prototype is more

advantageous for capturing the maximum sunlight with

increasing the average power by 34% in comparison with the

static solar system which using the optimal switching interval. According to the results and the experiments in this work, many

suggestions can be proposed to develop the tracking design for

the future such as studying the optimal switching interval for

larger solar panels. Also, replacing the control circuit of our

prototype system with another control circuit can consume less

energy such as STM32 Nucleo-64 development board with

STM32F401RE MCU.

REFERENCES

[1] A. Zakariah, J. Jamian, M. A. M. Yunus, “Dual-axis solar tracking system

based on fuzzy logic control and Light Dependent Resistors as feedback

path elements,” in 2015 IEEE Student Conference on Research and

Development (SCOReD), 2012.

[2] C. Alexandru, “The design and optimization of a photovoltaic tracking

mechanism,” in 2009 International Conference on Power Engineering, Energy and Electrical Drives, 2009, pp. 436-441.

[3] M. A. Usta, Ö. Akyazi, İ H. Altaş, “Design and Performance of Solar

Tracking System with Fuzzy Logic Controller,” in 6th International Advanced Technologies Symposium (IATS’11), Elazığ, Turkey, 2011, pp.

381-385.

[4] T. Tudorache, L. Kreindler, “Design of a Solar Tracker System for PV Power Plants,” Acta Polytechnica Hungarica, vol.7, 2010, pp. 23-39.

0

5000

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ins

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s

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min

s

30

min

s

40

min

s

50

min

s

55

min

s

1 h

r

2 h

rs

3 h

rs

4 h

rs

6 h

rsGen

erate

d E

ner

gy

Gain

in

J

Switching Interval Time

32.50%

33.00%

33.50%

34.00%

34.50%

5mins

10mins

20mins

30mins

40mins

50mins

55mins

1 hr

Eff

icie

ncy

%

Switching Interval Time

23

[5] A. Dolara, F. Grimaccia, S. Leva, M. Mussetta, R. Faranda, M. Gualdoni,

“Performance Analysis of a Single-Axis Tracking PV System,” IEEE

Journal of Photovoltaics, 2(4), 2012, pp. 524-531.

[6] A. R. Waheed, “Implementation of solar energy tracking system using microcontroller (Unpublished master's thesis),” Electrical Engineering,

University of Technology-Iraq, 2013.

[7] S. Ozcelik, H. Parkash, and R. Challoo, “Two-axis solar tracker analysis and control for maximum power generation,” Procedia Computer

Science, vol. 6, pp. 457–462, 2011.

[8] A. A. Bin Azman, “A solar tracking system with multiple input parameters for efficiency optimization (master's thesis),” Faculty of

Electrical Engineering, Universiti Teknologi Malaysia, 2014.

[9] M. A. Bin Shukor, “Design of low power automatic sun tracking system using arduino uno (master's thesis),” Faculty of Electrical Engineering,

Universiti Teknologi Malaysia, 2015.

[10] K. Vijayalakshmi, B. Narendra, K. S. Anjaneyulu, “Designing a Dual Axis Solar Tracking System for Maximum Power,” Journal of Electrical

& Electronic Systems, 5(3), 2016, pp. 1.

[11] D. R, B. V, R. R, P. A, D. S, M. P, “Comparison of Efficiencies of Solar Tracker systems with static panel Single Axis Tracking System and Dual-

Axis Tracking System with Fixed Mount,” International Journal of

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Sun Tracking System for Maximum Solar Energy Generation,” American

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Using LabVIEW,” Journal of Automation and Control Engineering, 1(4), 2013, pp. 312-315.

24

Optimum Coordination of using Overcurrent Relay

using Two Phase Simplex and Ant Colony

Optimization Algorithm

Cheyaden Savio Aswin1, Dr.O.V.Gnana Swathika1,* VIT University Chennai, India

*gnanaswathika.ov@vit.ac.in

Abstract— Power Systems are prone to damage due to

overcurrent which is a result of faults like ground faults, line

faults, short circuit etc. To minimize the damage caused by these

faults suitable protection systems must be in place. The

protection systems consist of a primary system and a backup

system with proper coordination between the two systems (i.e.

their tripping time) in order to ensure proper clearance of faults

in minimum time. In this paper, the optimization of overcurrent

relays which are used primarily as backup systems against these

faults are analyzed. The application of Ant Colony Optimization

and Two Phase Simplex Algorithm in radial system is done to

obtain the time multiplier settings of the relays. This enables us to

achieve proper coordination between the overcurrent relays in

the network.

Index Terms— Ant Colony Optimization, Protection, Radial

Distribution, Swarm Intelligence, Two Phase Simplex Method.

I. INTRODUCTION

Electric Power is transmitted to the consumers from

generation centers through distribution systems. The electric power needs to be transmitted at low voltage levels to minimize loss and is stepped down at substation. Using primary feeders this stepped down electric power is fed to the distribution transformers. The type of distribution used depends on location and economics, but it is easier to coordinate current based devices if they are in a radial network [1-4].

A radial network consists of one power source and group of customers in series. All the customers are affected if there is a power failure. In order to minimize the damage to the system and interruption of power supply the importance of reliable protective systems is paramount and this is done keeping in mind that the occurrence of abnormalities in power systems is unavoidable [5-10]. Distribution systems in general, have two lines of defense a primary protection system and a backup system. The primary system acts as the first line of defense against faults the backup system comes into play in case of failure of the primary system [11-14]. The backup system would operate only after a certain period of time known as Coordination Time Interval (CTI) in order to give a chance to the primary system to operate [15-17]. The primary system consists of overcurrent relays. With the help of current and voltage transformers, the relays detect faults. The settings

of the relay must be done in a way that the relay located closest to the fault should have the minimum time of operation. Nevertheless, complex situations may arise which can lead to the faulty operation of relays. Hence, optimum coordination between relays is necessary [18].

This paper implements the use of Swarm Intelligence

Algorithm namely Ant Colony Optimization and Two Phase

Simplex Optimization to find the optimum Time Multiplier

Settings (TMS) of the relays in order to ensure minimum time

of operation of relays.

II. OVERCURRENT RELAY COORDINATION OF A

TWO-BUS RADIAL SYSTEM

There are two types of overcurrent relays: directional and non-directional relays. As Directional overcurrent (DOC) relays, do not require coordination with the relays behind them, they are preferred over the non-directional relays.

Figure1 : A radial two bus system

A radial feeder with two sections and feeders is shown in Fig 1. For a fault at F, relay R2 will be the first to operate. R2 operates after 0.1 sec time after the inception of the fault in order to protect the relay from transient current surges in the relay. Relay R1 should operate after a fixed time interval, CTI, which is equal to the sum of operation time of circuit breaker at bus 2, overshoot time of relay R2 and 0.1 sec. Similarly, these conditions can be expanded to larger networks. Using these constraints, the system is formulated as a Linear Programming Problem (LPP) and solution is obtained using the Two Phase Simplex and Ant Colony Optimization Algorithm. In this manner, we obtain the TMS and time of operation of relays R1 and R2.

25

A. Problem Formulation

DOC relays require two main parameters to operate

namely relay current settings and the time TMS [8]. Relay

settings depend on the maximum load current in the feeder.

TMS is obtained by minimizing the objective function [9-15]:

n

Min z = Σ topi (1)

i=1

where,

topi operating time of the primary relay i, for a fault at i

under the following constraints [2]:

B. Bounds on Operating Time –

topimin topi topimax (2)

where,

topimin the minimum time required for operation of

the relay at i for fault at ‘i’.

topimax time required for operation of the relay at i

for a fault at ‘i’.

C. Coordination Time Criteria –

Coordination time is the minimum time required

between operation of two relays [2].

tbopi -- topi ≥ Δt (3)

where,

tbopi - the operating time of the backup relay i, for a

fault at ‘i’.

Δt - the coordination time interval (CTI) [2].

D. Relay Characteristics –

Normal inverse definite minimum time (IDMT)

characteristics are assumed for all relays [2,5].

𝛼= 𝜆 (4)

(𝑃𝑆𝑀)𝛾−1

where,

λ is 0.14and is 0.02.

Plug multiplier setting (PSM) is given by

PSM = If (5)

CT ratio x Relay Setting

where,

If is the fault current (in A).

topi = λ ∗ (TMS) ∗ ((PSM)γ– 1) −1 (6)

i.e. topi = α(TMS) (7)

Substituting (7) in (1) gives the objective function as:

n

Min z = Σ αi(TMS)i (8)

i=1

The value of TMS is hence determined.

III. TWO PHASE SIMPLEX ALGORITHM

The two phase method is used to solve a linear

programming problem. It is used to retain optimality while

bringing the primal set of equation back to feasibility. It is

useful for re-optimizing a problem after a constraint is added

into a problem or some parameters of the same are changed so

that the previous optimal basis remains no longer feasible [4].

The algorithm is [4, 5]:

A. Algorithm

1. Start.

2. Try and convert the linear programming problem in

maximization form.

3. Check if all constraints are in ≥ form, if not then

convert them into the same.

4. Introduce slack variables to remove inequalities and

transform them into equalities.

5. Create a table by considering artificial coefficients as

basis variables.

6. Initialize the Cq values of non basis variables by

comparing it from the given equation.

7. Now fill up the table by entering all the values of

basis as well as non basis variables and also the RHS

column form the given constraint equations.

8. The Zq values of all the non basis variables are

calculated by the summation of product of cost and

the corresponding non basis values there after

calculate the values of Zq-Cq.

9. Now check whether all the values of Zq-Cq are

positive or not, if so then stop the process.

10. The column having most negative value of Zk-Cq is

taken as key column and the corresponding column

26

variable will be treated as the one that enters the

basis.

11. The values in the RHS column are divided by the

values in the corresponding key column for each row.

The row having minimum such values will be taken

as key row. The values obtained if found to be

negative will not be considered as key row.

12. The row having minimum value obtained from the

previous step, the variable corresponding to that row

leaves the basis.

13. The element corresponding to key row and key

column is taken as pivot element.

14. Make pivot element as one and make the

corresponding elements as zero by using row

transformation method in order to obtain a modified

table.

15. Develop the next improved solution by repeating the

process till all Zq-Cq becomes non-negative.

16. Repeat the same process for the second phase

iterations with the only difference in costs that are

taken as original coefficients of objective function,

until all the values of Zq-Cq becomes non negative.

17. The right hand side (RHS) column values obtained

in the final step gives the optimized solution.

18. end

IV. ANT COLONY OPTIMIZATION ALGORITHM

The Ant Colony Optimization(ACO) Algorithm uses the behavior of forging ants to determine the optimum solution of a problem. While foraging for food ants tend to distribute over an area to speed up the process. To indicate a path has been explored, each ant secrets pheromones while travelling. Thus the pheromone concentration for the most travelled path increases when the ants find the food source and the paths begin to overlap. As more ants follow the path with the highest pheromone concentration the pheromone in the other paths begin to evaporate with time. Thus, they compute the optimal path.

In this paper we applied the traditional ACO algorithm to solve an LPP in the continuous domain by thorough the method of recursive discretization. We used the constraints of the problem to define the boundaries of our solution. The algorithm is explained below.

A. Algorithm

1. Create Initial population of ants;

2. Set the boundaries of space for search using

constraint equations.

3. Discretize continuous domain into clustered points.

At first large size clusters are formed.

4. Spawn the ants at random location in space.

5. While(discretization factor > Set Value)

6. for i=1:n (all n ants)

7. Calculate the desirability of ants next location using

cost function and pheromone presence.

8. Move ant to most desirable point and increment the

pheromone value of that point.

9. end if

10. Ants cannot move from presents location.

11. Choose point with least cost value.

12. Define new space.

13. Decrement discretization.

14. end

First a fixed population of ants are spawned in a space defined by the constraints. The ants begin foraging by moving from one point to another by determining the desirability of the point and choosing the point with maximum desirability. The desirability of a point is determined by the function

Pm,n = (ταm,n)*(ηβ

m,n) (9)

Σ(ταm,n)*(ηβ

m,n)

Where m,n are the x and y coordinates of a point.

τ amount of pheromone on that point and α is the factor which controls the influence of pheromone.

η desirability of point based on cost function defined by the equation to be maximized and β is the factor which controls the influence of the cost function.

After moving to a point the ant updates the pheromone value of the point using the equation.

τmn = (1-ρ)τmn + ΣΔτkmn (10)

where

ρ pheromone evaporation rate

τkmn amount of pheromone deposited by the kth ant.

Δτkmn is calculated by the formulae,

Δτkmn = Q (11)

Lk

where

Q constant factor

Lk cost of the kth ant’s tour which in this case is the value of the cost function.

At the end of each iteration the minimum points of

the function are determined and the point which gives the least

value is defined as the new space for next iteration with an

decrease in the discretization factor.

V. RESULTS

2-bus Radial system

27

Consider the 2-bus radial system shown in Figure 1. It includes a 220 kV, 100 MVA source (also taken as the base kV and base MVA of the system). The CTI for the relay is taken as 0.57 s. The maximum fault current just beyond relay R1 is 2108A and beyond R2 is found to be 1703 A. Using the equations (2) and (4) the values of α are calculated and tabulated as shown in Table 1. Here we assume the upper limit of the TMS of both relays as 1.2 and the lower

R2 being the primary relay operates first when the fault occurs at F. Let R2 operate 0.2 s after the fault inception to ensure that it does not operate for current surges. Relay R1 should operate after the CTI, which equals to the sum of operating time of circuit breaker (CB) at bus 2, overshoot time of relay R1 and 0.2 sec.

TABLE 1

Relay Constants

FAULT LOCATION RELAY RA- Ap

CONSTANTS RELAY RB- Ap

CONSTANTS

JUST BEYOND A 3.21

JUST BEYOND B 7.38 3.57

Let x1 and x2 be TMS values of relay R1 and R2 respectively.

3.57*x1 – 3.57*x2 ≥ 0.57 (12)

Subject to the constraint,

3.21*x1 ≥ 0.2 (13)

And

3.57*x1≥ 0.2 (14)

The upper limit is taken at 1.2.

For (ACO) we set the discretization factor to 1 at first

and then decrement by one tenth of the original value for each

iteration for 5 such iteration to get our value our minimum

point to an accuracy of 10-5. A population is chosen of 50 ants

to start with as this helps to arrive at a minimum point faster.

The results of ACO are compared with the Two Phase

Simplex Algorithm and are tabulated as shown in Table 2.

Table 2 TMS values of relays

TMS of Relays

X1 X2

Two

Phase

simple

x

.215 .056

ACO 0.11574 0.05851

VI. INFERENCE

To optimize the TMS, two algorithms namely Ant

Colony Optimization and Two Phase simplex method have

been compared. It can been deduced that using ACO, the

optimization is higher and more effective

VII. CONCLUSION

The protection of distribution system from

overcurrent faults is very important for power system

protection engineers. OC relays are predominantly used in

radial distribution networks and are expected to identify and

isolate faults instantly. This paper compares the effectiveness

of Swarm Intelligence Algorithm ACO and Two Phase

Simplex Algorithm in finding the optimized solutions for time

multiplier setting and time of operation of relays. These

algorithms can also be conveniently extended to larger

distribution networks. Moreover, to better understand

distribution networks and to perceive its ability to minimize

and isolate faults, other optimization can be undertaken to

obtain case specific results.

REFERENCES

1. O.V.G. Swathika, and S. Hemamalini, “Prims-Aided Dijkstra Algorithm for

Adaptive Protection in Microgrids,” IEEE Journal of Emerging and Selected

Topics in Power Electronics, vol. 4(4), pp.1279-1286, 2016.

2. O.V.G.Swathika, A. Das, Y. Gupta, S. Mukhopadhyay, and S. Hemamalini,

“Optimization of Overcurrent Relays in Microgrid Using Interior Point

Method and Active Set Method,” In Springer Proceedings of the 5th

International Conference on Frontiers in Intelligent Computing: Theory and

Applications, pp. 89-97, 2017.

3. A. Gupta, O.V.G. Swathika, and S. Hemamalini, “Optimum Coordination

of Overcurrent Relays in Distribution Systems Using Big-M and Dual

Simplex Methods,” In IEEE Computational Intelligence and Communication

Networks, pp. 1540-1543, 2015.

4. O.V.G. Swathika, S. Mukhopadhyay, Y. Gupta, A. Das, and S.

Hemamalini, “Modified Cuckoo Search Algorithm for Fittest Relay

Identification in Microgrid,” In Springer Proceedings of the 5th International

Conference on Frontiers in Intelligent Computing: Theory and Applications,

pp. 81-87, 2017.

5. O.V.G. Swathika, S. Hemamalini, “Review on Microgrid and its Protection

Strategies,” International Journal of Renewable Energy Research, vol. 6(4),

pp.1574-1587, 2016.

6. O.V. Gnana Swathika, Indranil Bose, Bhaskar Roy, Suhit Kodgule, and S.

Hemamalini, “Optimization Techniques Based Adaptive Overcurrent

Protection in Microgrids,” Journal of Electrical Systems, Special Issue 3, vol.

10, 2016.

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Controller for Protection in Radial Distribution System. In Springer Advanced

28

Computer and Communication Engineering Technology, vol. 362, pp. 195-

209, 2016.

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Protection for Distribution Systems With High Penetration of Distributed

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9. C. Vassilis Nikolaidis, Evangelos Papanikolaou, and S. Anastasia

Safigianni. “A Communication-Assisted Overcurrent Protection Scheme for

Radial Distribution Systems with Distributed Generation,” IEEE Transaction

on Smart Grid, 7(1), 114-123, 2016.

10. H.H. Zeineldin HH, E. F. El-Saadany, and M.M.A. Salama. “Distributed

Generation Micro-Grid Operation: Control and Protection,” In Power Systems

Conference: Advanced Metering, Protection, Control, Communication, and

Distributed Resources, pp. 105-111, 2006.

11. P. Prashant Bedekar, R. Sudhir Bhide, and S. Vijay Kale, “Optimum

Coordiantion of Overcurrent relays in Distribution system using Dual Simplex

Method”, In IEEE International Conference on Emerging Trends in

Engineering and Technology, pp. 555-559, 2009.

12. Y.G. Paithankar, and S.R. Bhide, “Fundamentals of Power System

Protection,” Prentice Hall of India Private Limited, New Delhi, 2007.

13. Badri Ram, and D.N. Vishwakarma, “Power System Protection and

Switchgear,” Tata McGraw Hill Publishing Company Limited, New Delhi,

2008.

14. B. K. Manohar Singh, B. K. Panigrahi and A. R. Abhyankar, “Optimal

Overcurrent Relay Coordination in Distribution System”, In IEEE

International Conference on Energy, Automation, and Signal, pp. 1-6, 2011

15. K. Deb.”Optimization for Engineering Design –Algorithms and

Examples,” Prentice Hall of India Private Limited, New Delhi, 2006.

16. P.P. Bedekar, and S.R. Bhide, “Optimization of multivariable nonlinear

functions using genetic algorithms,” In IEEE International Advance

Computing Conference, 2009.

17. R. Madhumitha, P. Sharma, D. Mewara, O.V.G. Swathika, and S.

Hemamalini, “Optimum Coordination of Overcurrent Relays Using Dual

Simplex and Genetic Algorithms”, In IEEE International Conference on

Computational Intelligence and Communication Networks, pp. 1544-1547,

2015.

18. Chao-Rong Chen, Cheng-Hung Lee, and Chi-Juin Chang, “Optimal

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Approach”, International Journal of Electrical Power & Energy Systems,

45(1), pp.217-222, 2012.

29

An Improved Rules-based Control of Battery Energy

Storage for Hourly Power Dispatching of

Photovoltaic Sources

M. A. Jusoh and M. Z. Daud School of Ocean Engineering, Universiti Malaysia Terengganu,

21030 Kuala Nerus, Terengganu, Malaysia.

zalani@umt.edu.my

Abstract—Battery energy storage (BES) system is effective in

smoothing and dispatching the fluctuation output from solar

photovoltaic (PV) sources. This paper presents an improved rules-

based control scheme for BES with the goal of minimizing the

fluctuation output from PV sources while ensuring the operational

constraints of BES are regulated at the specified ranges for the

safety purposes. The control scheme is developed based on the

desired operational constraints of BES such as state-of-charge

(SOC) and charge/discharge current limits. The simulation studies

were carried out by using Matlab/Simulink to evaluate the

effectiveness of the proposed control scheme on the 1.2 MW PV

system data obtained from a site in Malaysia. Furthermore, a

comparative study of the proposed control scheme with the

existing methods has been done to address the effectiveness of the

control scheme. The simulation results show that the proposed

control scheme can effectively minimized the output power

fluctuations of the PV sources and dispatching the output on an

hourly basis to the utility grid with the efficiency up to 94.47%.

Finally, the comparison results also illustrates the proposed

control scheme as the most effective controller compared to the

other type of controllers studied previously.

Index Terms—Power fluctuation mitigation; Battery energy

storage; Lithium-ion battery; Photovoltaic system.

I. INTRODUCTION

Solar photovoltaic (PV) energy source is well known for its

unpredictable and inconsistent output due to the intermittent

nature of solar irradiance and temperature [1]. High penetration

of unpredictable and inconsistence of solar PV output into

utility grid system caused many problems including voltage and

power fluctuations and other power quality problems.

Integration of solar PV system with battery energy storage

(BES) system is proven to be effective on minimizing such

problems provided that a proper control scheme is designed and

managed [1-4]. Various types of batteries are potential to be

integrated to solar PV system for power fluctuation mitigation

purposes such as Lead acid (LA), Lithium-ion (Li-ion) and

Nickel Cadmium batteries [5]. However, high cost of BES

system is considered one of the obstacles that require further

attention. For many cases, studies associated to developing a

robust and efficient control method for BES are of significant

importance to provide a cost-effective BES system.

There are many types of control schemes for BES system

were proposed in the literature for the purpose of smoothing

fluctuation output of renewable energy sources. However, few

researches have been focusing on the smoothing fluctuation

output with constant output power dispatching. In [2], the

optimization-based state-of-charge feedback (SOC-FB) control

scheme for the valve-regulated lead acid (VRLA) BES has been

proposed to regulate the SOC of BES according to the desired

operational constraints such as SOC and current limits during

the smoothing and dispatching processes. The authors proposed

genetic algorithm-based parametric optimization with overall

smoothing and hourly dispatch efficiency recorded equal to

84%. Consequently, heuristic optimization-based studies have

been investigated in [3] using other algorithms such as

gravitational search algorithm (GSA), and particle swarm

optimization (PSO). For this case, the results for the fluctuation

mitigation efficiency was measured 89.91% using GSA

approach. However, long computation times and accurate BES

system model were required for the optimization processes. In

[4], a simple approach based on the rules has been proposed.

The rules in the control scheme was determined based on the

desired operational constraint of BES system. The results

showed the proposed rules-based control scheme effectively

smoothing the fluctuation output of PV system. However, it was

failed to sustain the BES power at the desired level. In this

regards, to overcome the associated issues in [2-4], this paper

introduces an improved rules-based control scheme for BES

system. The objective of the study is to develop a simple and

robust control scheme for BES system so that the fluctuation

output can be smooth out and dispatch out to utility grid system.

The rest of the paper is organized as follows: Section II

describes the details of the proposed control scheme and the

simulation set-up. Section III presents the results and discussion

from the simulations. Finally, Section IV concludes the paper.

II. METHODOLOGY

In the present study, a typical AC-coupled PV-BES structure

for power smoothing and power dispatch is presented in Figure

1. The PV and BES systems are parallel connected to the PCC

via bi-directional voltage-sourced-converter, VSC (i.e. PV-

VSC and BES-VSC). The BES-VSC system is responsible in

regulating the fluctuated output of PV system (PPV) through

charge and discharge of BES power (PBES). In order to provide

safety and economical operation of BES system, the BES

operation is subjected to several desired operational constraints

as described in equation (1)-(3), where SOCBES,min and

30

SOCBES,max are the minimum and maximum level of SOC

operating ranges of BES (SOCBES). The IBES,min and IBES,max are

the minimum and maximum allowed current of BES (IBES) and

VBES,min and VBES,max are the operational constraints of BES

voltage (VBES). The SOCBES,min and SOCBES,max are set to 0.3 p.u

and 0.9 p.u, respectively, which is 60% of the total capacity of

BES. The SOCBES constraint is used to prevent the BES from

the over-discharge and over-charge. The IBES constraint is set

to ±1×CBES based on the BES-VSC current limit, while the VBES

constraint is set to 10% of the BES rated voltage. The VBES

operational is used to prevent the BES from the breakdown.

max,min, )( BESBESBES SOCtSOCSOC (1)

max,min, )( BESBESBES ItII (2)

max,min, )( BESBESBES VtVV (3)

Figure 1: General structure of PV-BES system

The BES-VSC employed the current-mode control strategy

that has two loops as presented in Figure 1. The details of

current-mode control are discussed in [6]. The outer control

loop is used to generate the reference current (IBES,ref) signal

either to charge or discharge while inner control loop is used to

generate the switching signals for the BES-VSC. In order to

generate the optimal IBES,ref for output power smoothing and PV

power dispatch, control scheme is introduced in outer control

loop as discussed in the following section.

A. Development of Control schemes for BES system

i. PSO-based SOC-FB control scheme

This optimization-based SOC-FB control scheme of BES

system has been proposed in [2] for hourly power dispatch of

PV system. In this paper, the optimization-based control

scheme is developed for the purpose of comparison of the

control scheme performances. Figure 2 illustrates the overall

diagram of optimization-based SOC-FB control scheme. The

aim of the control scheme is to minimize the deviation between

hourly forecasted power reference, PSET and PPV and generate

the optimal IBES,ref for BES system while ensuring the

operational constraints of BES are regulated at the specified

ranges. As illustrates in the Figure 2, PSO algorithm is used to

find the optimal parameters of SOC-FB control scheme and the

capacity of the BES system. The objective function of the

optimization is determined based on the Equation (4), where the

vector x represents the SOC-FB control scheme parameters

(MSOC, TSOC) and the capacity of BES system (CBES).

( ) −= dt(t)P(t)POF(x) GSET2

min (4)

Figure 2: Optimization-based control scheme

ii. Improved-rules based control scheme

The conventional rules-based control scheme of BES system

for hourly dispatch of PV system output has been introduced in

[4] with the same objective as the optimization-based SOC-FB

control scheme. The conventional rules-based is simple, require

minimal computation times and does not required accurate BES

system model compared to optimization-based control scheme.

However, the conventional rules-based control scheme can only

control the BES from over-charge and over-discharge but not

able to sustain the BES power at the desired level. Such an

imperfection makes the conventional controller unable to

support the continuous BES power required for dispatching

operation of intermittent PV output power.

The rules of the controller are divided into two parts: i.e. rules

for SOCBES constraint, and IBES constraints, respectively. For

SOCBES constraint, the rules are created to guarantee the SOCBES

to be kept within the desired limit (SOCBES,min and SOCBES,max)

during the smoothing and dispatching process. Meanwhile, in

the IBES constraints, the rules are developed to limit the charging

and discharging current of BES at the desired operational limit

(IBES,min and IBES,max). In the present work, some improvements

to the conventional rules-based control scheme have been

suggested and developed. Overall structure of the improved

DC

DC

DC

AC

DC

AC

PV System PV-VSC

BES-VSC DC Bus

PCC

Grid system

Lf 2

Lf 1

PPV

PBES

PG

CB

PV-conv

with MPPT

control

BES

Switching signal

Inner control loop

Power smoothing and hourly power

dispatch control scheme in outer

control loop

Current-mode Control scheme

PSET

’

PPV

31

control scheme is illustrates in the Figure 3. As illustrates in the

figure, the SOC power correction of (PSOC) is added to the

conventional rules-based control scheme to ensure the SOCBES

is maintain at the desired SOC level (SOCBES,ref) from the

beginning of the process until the end. The PSOC in unit of MW

is applied to PBES,tar signal, where positive and negative value

of PSOC represents the shortage and the surplus energy of BES

to maintain SOCBES at SOCBES,ref, respectively.

Figure 3: Improved rules-based control scheme

B. Simulation set-up and evaluation of the performance of

the control methods

The simulation study is carried out using Matlab software.

The PPV and PSET data are obtained from the daily average of

1.2 MW PV system output measured in Malaysia [2].

Meanwhile, Li-ion-types of PowerSim battery model in

Matlab/Simulink is used as BES energy storage. For the

optimization-based control scheme, the SOC-FB control

scheme is developed in Matlab/Simulink, while the PSO

algorithm for the optimization process is developed in M-file.

During the simulation process, the Matlab/Simulink is linked to

PSO algorithm in M-file and the processes running

simultaneously. The simulation process is terminated when the

PSO algorithm meet the optimal values at the optimal

condition. Meanwhile, for the improved rules-based control

scheme, the rules in the control scheme is implemented in

Matlab/Simulink using Matlab function block, where the

C/C++ code language is used to represent the rules.

In order to evaluate the robustness and flexibility of the

performance of the control schemes, the case studies of the

varying BES capacity are considered. The purpose of the BES

capacity case studies is to verify the effect of the BES capacity

to the control scheme performance. For this cases, the capacity,

CBES, is set to 0.25 MWh (416.7 Ah), 0.3 MWh (500 Ah) and

0.35 MWh (583.3 Ah), respectively. In addition, analysis of

simulation results is also given through evaluation using the

Performance Index (PI) [4], Battery Health Index (BHI) [7] and

Efficiency (ɳ) [2] as given in equations (5)-(7). The value of Nx

of equation (5) represents the number of occurrence of the

deviations, while dPx represents the deviation between, powers

delivered to grid, PG, with respect to power reference set-point,

PSET. The PI0 and PIBES of equation (7) represent performance

index without/with using BES, respectively. For dP criteria, it

is assumed that the deviations up to ± 0.1 MW are acceptable.

Meanwhile, for PI and BHI, a smaller values indicates the high

dispatching performance and the effective usage of BES device

within the safe operating limits.

𝑃𝐼 = ∑ 𝑁𝑥 × |𝑑𝑃𝑥| (5)

=

−=

T

t

refBESBES SOCtSOCT

BHI

1

2,)(

1 (6)

( ) 100/ 00 −= PIPIPI BES (7)

III. RESULTS AND DISCUSSION

The results are divided into two parts. The first part discusses

about the effects of improved control scheme to the dispatching

performance of the PV-BES system, whereas the second part

provides the effects of the BES capacity to the improved control

scheme performance and the PV-BES system dispatching

performance compared to other control schemes.

A. Dispatching performance of PV-BES system by using

improved rules-based control scheme.

Firstly, for the preliminary study, the simulation is carried out

to present the dispatching performance of PV-BES system

without control scheme. This case considers BES size of 0.3

MWh with initial capacity set at 60% of the total capacity. In

addition, it is assumed that the BES system will be disconnected

from the PV system if the SOCBES is outside the desired

operating constraints of BES. Figure 4 shows the results of the

dispatching performance of PV-BES system without control

scheme of BES.

Figure 4: Dispatching performance of PV-BES system without control scheme

From figure 4(a) and 4(b), it is evident that the difference in

accuracy of forecasted power set-point, PSET, affects the

dispatching performance of the PV-BES system without control

schemes. For the case of 100% accuracy of PSET, the output

power fluctuation of PPV is successfully smoothed and

dispatched to the grid while meeting all the desired operating

constraints until 7 PM in the afternoon. However, at 90%

accuracy of PSET, the output power fluctuation of PPV is

7 9 11 13 15 17 19

(a)

Po

wer

(M

W)

0.0

0.4

0.8

1.2

PG (100% accuracy of P

SET)

Time (hr)

7 9 11 13 15 17 19

(b)

SO

C (

p.u

)

0.0

0.2

0.4

0.6

0.8

1.0

SOCBES, max

SOCBES, min

with BES without BES

PG (90% accuracy of P

SET)

32

successfully smoothed and dispatched only from 7 AM to 8 AM

due to the disconnected BES system from the system. The BES

is disconnected from the system due to the SOCBES level that

has reached the SOCBES,min as illustrates in Figure 4(b). From the

results, it can be concluded that without control scheme applied

to the system, larger BES capacity is desired in order to keep

the BES continuously operated within the SOCBES level.

Therefore, to meet the acceptable dispatching performance

using minimum capacity of BES, the SOCBES needs to be

properly controlled.

Figure 5(a)-(d) presents the dispatching performance of PV-

BES system output power, VBES profiles, SOCBES profiles and

IBES profile at 90% accuracy of PSET using 3 different control

schemes, respectively. In this case, an optimal 0.287 MWh (478

Ah) of CBES that has been determined by using optimization-

based control is used. As shown in Figure 5(a), the dispatching

performance of PV-BES system by using improved rules-based

control scheme and optimization-based control scheme can

track the PSET perfectly while keeping the BES operational

constraints at the desired limits. As evident from the Figure

5(b)-(d), all operating constraints of BES are varied within the

desired operating ranges. There are some spikes exist in the

dispatching output mostly between 11 AM and 3 PM because

of the current block inside the controller for safe operation

purposes. Meanwhile, Figure 5(a) also illustrates the poor

dispatching performance of conventional rules-based control

scheme. The conventional rules-based nearly failed to track the

PSET perfectly in between 1 PM to 7 PM due to the insufficient

of BES energy.

Figure 5: Dispatching performance of PV-BES using different control

schemes

Figure 6(a)-(d) illustrates the histograms and the normal

distribution curves of dP for comparing the performances

without deployment of control scheme and with using 3

different control schemes, respectively. From normal

distribution in Figure 6(a)-(d), the percentage of occurrences of

unacceptable deviations are obtained. For the case of without

control scheme, percentage of occurrences of unacceptable

deviations is calculated equal to 42.1%, while for optimization-

based (SOC-FB), conventional rules-based and improved rules-

based control schemes are 0.08%, 3.64% and 0.01%,

respectively. The obtained results prove that, the performance

of the improved rules-based control scheme is better than

optimization-based SOC-FB, and conventional rules-based

control scheme, respectively.

Figure 6: Histogram and normal distribution of dP

Finally, Table 1 gives the details of extracted results from the

Figure 6(a)-(d). From the results, it clearly shows that the

improved rules-based control scheme is more efficient in

dispatching process with the performance index, PI, of 36.83

and efficiency of 94.5% compared to the other control schemes.

Besides that, in terms regulation of the state-of-charge, SOCBES,

using improved control scheme, the SOCBES is maintained at

minimum SOCBES of 0.43 p.u and the BHI measured around

0.0817. From the results, it can be concluded that the improved

control scheme can optimally smoothing the fluctuation of PPV,

and can extend the lifetime the of BES system.

B. Effect of capacity, CBES, to the dispatching performance

of PV-BES system

Table 2 presents the effect of BES sizes on the dispatching

performance for each control scheme, respectively. For the

7 9 11 13 15 17 19

(a)

Po

wer

(M

W)

0.0

0.4

0.8

1.2

PG of Improved rules-based

7 9 11 13 15 17 19

(b)

Vo

ltag

e (k

V)

0.60

0.64

0.68

7 9 11 13 15 17 19

(c)

SO

C (

p.u

)

0.0

0.5

1.0

Time (hr)

7 9 11 13 15 17 19

(d)

Curr

ent

(kA

)

-1.0

-0.5

0.0

0.5

1.0

PG of Optimization-based

PG of Conv. rules-based

0.35

0.16

0.00

-0.1

6

-0.3

5

12

9

6

3

0

dP (MW)

Occ

ura

nce

(%

)

0.14

0 .07

0 .00

-0.0

7

-0.1

4

24

18

12

6

0

dP (MW)

Occ

ura

nce

(%

)

0 .18

0.12

0 .06

0.00

-0.06

-0.1

2-0

.18

80

60

40

20

0

dP (MW)

Occ

ura

nce

(%

)

0.14

0.07

0.00

-0.0

7- 0

.14

30

20

10

0

dP (MW)

Occ

ura

nce

(%

)

(a) Without control scheme (b) SOC-FB Control

(c) Conv. Rules-based control (d) Improved Rules-based control

Mean=0.01962 Mean=0.01803

Mean=0.00978 Mean=0.01931

SD=0.12265 SD=0.02239

SD=0.04425 SD=0.01897

33

unacceptable of dP, the results are evaluated and analyzed

through the normal distribution of dP. For optimization-based

control scheme, the unacceptable of dP is reduced from 0.08%

to 0.01% if the size of BES changed from 0.287 MWh to 0.35

MWh, while for conventional rules-based, the results show

reduction from 3.64% to 2.81%. However, for the improved

control scheme, the unacceptable of dP can be reduced further

to nearly 0%. Based on the results, it can be concluded that by

using improved control scheme, the size of the BES can be

reduced that contributes minimum cost.

Table 1

Results of dispatching performance of PV-BES using different control scheme

(BES=0.287 MWh)

Parameters (A)

Control Methods

Optimization-

based SOC-FB

Rules-based

Conventional Improved

PV capacity (MW) 1.2

BES capacity, CBES

(MWh) 0.287 (478 Ah)

Initial state-of-charge,

SOCi (p.u) 0.6

Terminal

voltage, VBES

(kV)

Max 0.6580 0.6512 0.6593

Min 0.6268 0.6172 0.6285

State-of

charge,

SOCBES (p.u)

Max 0.6000 0.6000 0.6274

Min 0.4033 0.3009 0.4337

Current, IBES (kA) ± 0.478

Performance index,

PI 43.5681 109.0115 36.8371

Battery health

index, BHI 0.0996 0.2525 0.0817

Efficiency, (%) 93.4634 83.6447 94.4732

Table 2

Effects of BES size to the dispatching performance of PV-BES system

Parameters

(unit) BES size

(MWh)

Control Schemes

Optimization-

based SOC-FB

Rules-based

Conventional Improved

Unacceptable

of dP

(%)

0.25 9.58 5.49 0.09

0.287 0.08 3.64 0.01

0.35 0.01 2.81 0

Performance

index, PI

0.25 155.7277 117.2707 45.2869

0.287 43.5681 109.0115 36.8371

0.35 41.0042 98.7146 30.5195

Battery

health index,

BHI

0.25 0.2180 0.2494 0.0923

0.287 0.0996 0.2525 0.0817

0.35 0.0816 0.2539 0.0681

Efficiency,

(%)

0.25 76.6358 82.4056 93.2055

0.287 93.4634 83.6447 94.4732

0.35 93.8480 85.1896 95.4211

In terms of the PI, BHI and efficiency, the results are also

provided in Table 2, respectively. From the PI results, by using

0.35 MWh BES, the PI of improved rules-based can be

achieved up to 30.5. However, for optimization-based and

conventional rules-based, the PI are only reduced up to 41.0 and

98.7, respectively. In terms of the effects of the BES size to the

BES BHI, increased BES size can decrease or in other words,

improvise the BHI for the case using optimization-based and

improved rules-based control scheme, respectively. On the

other hand, the results are totally different to the case of

conventional rules-based controller. The decreasing BHI of the

former controller is due to reduction of the charging and

discharging depth level of BES. By using 0.35 MWh BES size,

the BHI for improved rules-based control scheme is 0.0681,

while for optimization-based and conventional are only 0.0816

and 0.2539, respectively. From the results, it is evident that the

increasing of BES size and the use of improved rules-based

controller can increase the lifetime of the BES. Finally, Table 2

also compares the efficiency of the control schemes. Based on

the results, the improved rules-based control scheme performed

at the highest efficiency compared to the other control schemes.

For example, using 0.35 MWh BES size, the efficiency of

improved rules-based control scheme is 95.4%, compared to the

efficiency of optimization-based and conventional control

scheme at 93.8% and 85.2%, respectively. Overall of the results

show 10.2% improvement of efficiency of the improved rules-

based control scheme compared to the conventional rules-based

controller.

IV. CONCLUSION

An improved rules-based control scheme for BES system to

smooth out and dispatch the fluctuation of PV system on an

hourly basis to the utility grid is presented. The operational

constraints for BES are considered to ensure safe operation of

the system whilst providing power regulation service

continuously. Simulation results shows good performance of

the proposed control scheme compared to other previously

developed methods through the analysis of efficiency that has

been measured around 94.47% (at BES = 0.287 MWh). The

results also show that only proposed control scheme can reduce

the unacceptable deviation completely by using 0.35 MWh BES

system. The BHI also the lowest: i.e. 0.0817 (at BES = 0.287

MWh) compared to other control schemes. The overall results

clearly indicate the capability of the proposed control scheme

in increasing the lifetime of the BES system when it is subjected

to continuous charge/discharge operations particularly in power

fluctuation mitigation of solar PV sources.

ACKNOWLEDGMENT

This work is supported by Ministry of Higher Education

Malaysia (MOHE), Malaysia under the Fundamental Research

Grant Scheme (FRGS), Vot No. 59418 (Ref:

FRGS/1/2015/TK10/UMT/02/1).

REFERENCES

[1] S. Shivashankar, S. Mekhilef, H. Mokhlis, and M. Karimi, "Mitigating

methods of power fluctuation of photovoltaic (PV) sources–A review,"

Renew. Sust. Ener. Rev., vol. 59, pp. 1170-1184, 2016.

[2] M. Z. Daud, A. Mohamed, and M. Hannan, "An improved control method of battery energy storage system for hourly dispatch of photovoltaic power

sources," Energ. Convers. Manage., vol. 73, pp. 256-270, 2013.

[3] M. Z. Daud, A. Mohamed, A. A. Ibrahim, and M. Hannan, "Heuristic optimization of state-of-charge feedback controller parameters for output

power dispatch of hybrid photovoltaic/battery energy storage system,"

Measurement, vol. 49, pp. 15-25, 2014.

34

[4] S. Teleke, M. E. Baran, S. Bhattacharya, and A. Q. Huang, "Rule-based

control of battery energy storage for dispatching intermittent renewable

sources," IEEE Trans Sustain Energy, vol. 1, pp. 117-124, 2010.

[5] M. Delfanti, D. Falabretti, and M. Merlo, "Energy storage for PV power plant dispatching," Renew. Energ., vol. 80, pp. 61-72, 2015.

[6] T. Suntio, T. Messo, and J. Puukko, Power Electronic Converters:

Dynamics and Control in Conventional and Renewable Energy Applications: John Wiley & Sons, 2017.

[7] T. T. Trung, S.-J. Ahn, J.-H. Choi, S.-I. Go, and S.-R. Nam, "Real-time

wavelet-based coordinated control of hybrid energy storage systems for denoising and flattening wind power output," Energies, vol. 7, pp. 6620-

6644, 2014.

35

Analysis of the Coexistence of Wi-Fi Networks and

Real-Time Positioning Systems for Data Trafficking

and Object Positioning.

G. Cuzco1, 2, H. Moreno2 1Universidad Nacional de Chimborazo.

2Escuela Superior Politécnica de Chimborazo.

gcuzco@Unach.edu.ec

Abstract—Due to the increasing behavior of connected devices,

the development of technologies such as wearables, smart cities,

and others, announce a saturation of WiFi networks at 2.4HGz,

reducing their performance and encouraging migration at 5GHz.

This paper describes the implementation of a real-time

localization system with IEEE standard 802.15.4-2011 in order to

determine the coexistence between WiFi networks operating in

the 5GHz band and real-time location systems. An experimental

study has been conducted in open and closed environments; the

location system has been implemented using the DW1000

tranceiver with UWB antenna. Traffic, speed and Cartesian

coordinate’s data were collected in each scenario, traffic and

speed data were collected with Wireshark and Colasoft Capsa

software packages, Cartesian coordinates were collected in

Matlab and in conjunction with the rest of the information

analyzed in SPSS. Being the purpose to analyze the coexistence

between WiFi systems and location systems, it has been possible

to determine the affectation in the dispersion of the data in the

location systems in real time. The results obtained will be useful

when planning electronic systems that use these technologies so it

is recommended to analyze the transmission channels trying to

keep them with conservative guard bands and the need to

improve the algorithms for data management in location systems.

Index Terms— Coexistence of Protocols; IEEE 802.11a; IEEE

802.15; Location Systems.

I. INTRODUCTION

Since its inception, wireless communications have played a

preponderant role to keep us connected everywhere,

depending on WiFi connections to maintain our productivity

standard, thus promoting the development of dedicated

technologies in the area of health, security, home automation

and the leverage of the expression of the internet of things

transforming from a future trend to a reality.

The location systems in outdoor areas are covered by global

positioning systems that we know as Gps [18] that are

responsible for measuring the arrival time of radio signals and

with this information, calculate their position.

Indoors, it is using triangulation methods and algorithms

based on received signal strength or arrival time, which are

used to improve performance by using Ultra Wide Band

(UBW) based transmission systems governed by the IEEE

802.15-2011 standard. Therefore, the analysis of the influence

of wireless channels that operate in the WI-FI bands with the

802.11a standard on the accuracy of a positioning system

which is implemented by triangulation will be considered as a

research problem of radio frequency signal level and other

methods using the Ultra-Wide band technique.

II. METHODOLOGY

A scheme has been used where a communication system

based on two computers operates that uses the IEE 802.11a

standard. In the same way, a real time localization system

(RTLS) has been implemented, which operates with the IEEE

802.15.4-2011 standard.

The systems will always operate under the same specific

conditions controlling the variable of separation between them

and reporting the variables that correspond to each system

which will be detailed later, the general scheme presented can

be seen in figure 1. The tests have been developed in two

scenarios, one in open environments and another scenario

called closed environments.

Figure 1: General operation scheme

A. Communication System

In the antennas used, the transmission channel has been

configured with Access Point mode with a center frequency of

5840MHz with a channel width of 40MHz

.

36

Figure 2: Wireless transmission scheme

SCENARIO A. Closed Environments

The wireless communication system is made up of two

antennas of the Ubiquiti brand, which are separated by a

distance of 6.5m in an office environment. For the analysis of

network traffic, software packages are used: Wireshark and

Colasoft Capsa, which allow monitoring and analyzing

communication networks. The values obtained by each

software are analyzed by IBM SPSS Statistics.

These values will be obtained in three cases: a) Ubiquiti

antenna at 3m from the RTLS system, b) Ubiquiti antenna at

6m from the RTLS system and c) RTLS system deactivated.

SCENARIO B. Open Environments

The wireless communication system is made up of two

antennas of the Ubiquiti brand, which are separated by a

distance of 30m in an open environment, the same ones that

were installed on concrete poles in the sector. For the analysis

of network traffic, it uses software packages: Wireshark and

Colasoft Capsa, which allow monitoring and analyzing

communication networks. The values obtained by each

software are analyzed by IBM SPSS Statistics.

These values will be obtained in three cases: a) Ubiquiti

antenna at 3m from the RTLS system, b) Ubiquiti antenna at

6m from the RTLS system and c) RTLS system deactivated.

B. Real Time Positioning System (RTLS)

The real-time positioning system is composed of three

devices called fixed anchors and an element of similar

characteristics called Tag, the system used corresponds to the

Decawave family. The operating model used is shown in

Figure 3.

Figure 3: RTLS model used

RTLS anchors

The cards assigned as anchors have been installed at the

same height, the differences in mounting height influence in

the reduction of the location accuracy, in the same way the

installation of the anchors with line of sight (LOS) between

the cards

The propagation and detection model has been selected in

which one of the anchors reports the information to the PC

and, the mobile TAG does not exert additional actions, in this

way the anchors provide the necessary information to estimate

the position of the device assigned as TAG .

Tranceiver Decawave DW1000

The function of the tranceptor used is constituted by a single

Ultra-Wide Band (UBW) chip that consists of a transmitter

and an analogue receiver that through a digital tranceiver,

through an SPI interface is linked to the external Host. An

internal switch switches the antenna port to the TX / RX

function, transmission / reception.

Figure 4: DW1000 block Diagram

UWB antenna

The RF connection to the outside of the tracker DW1000 is

made through a pair of 100Ω differential pins which is

designed to work at a frequency of 3 to 8 GHz with an omni-

directional radiation pattern, provides a gain of 2.2 dBi at 4

GHz and 3.3 dBi at 6.5 GHz as seen in Figure 5.

37

Figure 5: UWB Antenna

Figure 6: Radiation Patterns: a) Azimuth plane theta 900, b) Elevation phi

00.

Figure 7: Maximum Gain antenna

III. RESULTS

The results are classified in the following:

1) Results of network traffic analysis

2) Location accuracy results (coordinates)

For this, two scenarios have been chosen: scenario A, closed

environments and; Scenario B, open environments, in each

scenario the two tests are planned, the data transmission and

the location system.

A. Analysis of network traffic

These values will be obtained in three cases:

a) Ubiquiti Antenna 3m from the RTLS system,

b) Ubiquiti Antenna 6m from the RTLS system and

c) RTLS system deactivated

SCENARIO A. Closed Environments

Table 1

Analysis of the network with the Colasoft software

Case Bytes

sent

(MB)

Packet

sent

Lost

Bytes

(MB)

Lost

Packet

Case

A

409,67 283,046 0,008 0,176

409,72 283,097 0,008 0,174

409,67 283,071 0,007 0,172

409,69 283,075 0,008 0,175

409,8 283,827 0,008 0,183

Case

B

409,67 283,082 0,007 0,17

409,67 283,07 0,007 0,169

409,67 283,072 0,007 0,169

409,67 283,097 0,007 0,17

409,7 283,675 0,007 0,169

Case

C

409,68 283,102 0,008 0,175

409,67 283,098 0,007 0,17

409,67 283,071 0,007 0,17

409,7 283,102 0,008 0,176

409,67 283,086 0,007 0,173

a)

c)

b)

38

SCENARIO B. Open Environments

Table 2

Analysis of the network with the Colasoft software

Caso

Bytes

sent

(MB)

Packet

sent

Lost

Bytes

(MB)

Lost

Packet

Case

A

409,69 283,075 0,008 0,175

409,7 283,102 0,008 0,176

409,67 283,097 0,007 0,17

409,72 283,097 0,008 0,174

409,67 283,046 0,008 0,176

Case

B

409,67 283,082 0,007 0,17

409,67 283,07 0,007 0,169

409,8 283,827 0,008 0,183

409,7 283,675 0,007 0,169

409,68 283,102 0,008 0,175

Case

C

409,67 283,072 0,007 0,169

409,67 283,071 0,007 0,172

409,67 283,086 0,007 0,173

409,67 283,071 0,007 0,17

409,67 283,098 0,007 0,17

In each case the trend of the behavior of the information has

been recorded as shown in table 3-1 and 3-2. The channel has

been verified its behavior with the spectrum analyzer as

indicated in figure 6.

Figure 6: Simultaneous behavior

A. Analysis of the position of objects

The real-time positioning system based on the DW1000

decawave tranceiver has been implemented in a closed

environment of 7m * 7m, for which five operating points have

been selected and the coordinates physically marked in both x

and y. The influence on the variable z is not analyzed in the

present project, so it has remained constant at 1m in height.

Table 3

Coordinates to perform the test

POINT X(m) Y(m)

P1 1 3.3

P2 2 2.5

P3 3.5 1.5

P4 4.5 0.7

P5 6.7 -0.4

The data collection is done at the distances established in

the initial parameters and its result is shown in Figure 7.

Figure 7: Fixed coordinates and coordinates with presence of interfering

signal (blue)

Similarly, the location of the antenna of the data link is

modified by moving it to a distance with less affectation, in

this case the distance to the nearest antenna is located at 6m

and the position data is recorded under these conditions.

Figure 8 shows the superimposed data of real position,

position without verified interference and position with the

operation in the conditions described above, the behavior of

the data is visible and is analyzed with statistical measures.

[m]

[m]

39

Figure 8: Fixed coordinates and coordinates with presence of interfering

signal distance two (blue)

As a result of the tabulation of the variations of the

dispersion of the measured data through the standard deviation

as a function of the distance, figure 9 is obtained, where it is

observed that the deviation decreases as the distance increases.

Figure 9: Behavior of the standard deviation

IV. CONCLUSIONS

In the present work an experimental procedure has been

developed to determine the affectation produced by the

wireless networks that operate at a frequency of 5.8GHz

causes the dispersion in the data collected by a location system

that uses the tranceiver DW1000 operating at close

frequencies.

The affectation found depends on the distance between the

two systems, which is more noticeable when they are carried

out in open environments, finding that at a greater distance,

the affectation is less.

In closed environments, the dispersion in the data is greater

in the positioning system even without the presence of

disturbances in the frequency band, this is due to the fact that

due to the method used for localization, it has effects on walls

and objects that change or delay the path of the signals.

. Acknowledgments The authors would like to thanks to the

Corporación Ecuatoriana para el Desarrollo de la

Investigación y la Academia -CEDIA-, for financing the

project “Control Coordinado Multi-Operador aplicado a un

robot Manipulador Aéreo”, – CEPRA-XI- 2017-06, for the

support to develop this paper.

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positioning system. Dept. of Electrotechnics, Faculty of Electrical

Engineering, University Pardubice.

[18] Marek Pola, L. Z. (2015). Measurement on precise indoor

positioning system in Real Enviroment. Dept. of Electrotechnics,

Faculty of Electrical Engineering, University Pardubice. [19] Mohammadreza , Y., & Bradford G., N. (s.f.). Obtenido de

http://www.cs.unb.ca

[20] Mok, E., Xia, L., Retscher, G., & Tian, H. (s.f.). A case study on the feasibility and performance of an UWB-AoA real time location

system for resources management of civil construction projects.

Journal of Applied Geodesy. [21] Popp, J., & Lopez, J. (2015). Real Time Digital Signal Strength

Tracking for RF Source Location. University of Washington, Seattle.

[22] Prieto Blázquez, J. (s.f.). Introducción a los sistemas de

comunicación inalámbricos. Universitat Oberta de Catalunya. [23] W.J. Lee, W. L. (s.f.). IEEE/ASME International Conference on

Advanced Intelligent Mechatronics. Design of Applications on

Ultra-Wideband Real-Time . [24] Xiong, Z., Song, Z., Scalera, A., Ferrera, E., Sottile, F., Brizzi, P., .

. . Spirito, M. (2013). Hybrid WSN and RFID indoor positioning

and tracking system. EURASIP Journal on Embedded Systems. [25] Zhao, L., Psota, E., & Pérez, L. (2014). A Comparison Between

UWB and TDOA Systems for Smart Space Localization. University

of Nebraska - Lincoln.

[m]

[m]

40

CHS Application on Novel Coplanar Routing

Azniza Abd Aziz, Chaitanya Sreerama

azizniza@gmail.com

Abstract— Nowadays, the demands on higher bandwidth

computational performance has rapidly increased. At the same

time, increasing the platform and system size is not an option. This

brings new design challenges since the system bus will suffer signal

integrity degradation and limit performance. As system sizes

shrink, signal channels come closer together and crosstalk noise

will increase further limiting bus performance. In this paper we

will introduce a novel coplanar routing procedure based on the

application of “Crosstalk-Harnessed Signaling” (CHS) that will

achieve a system with higher bandwidth in small form-factor. The

CHS concept will help tackle the crosstalk problem and a Novel

Coplanar routing scheme will help increase the maximum bus

bandwidth per volume. CHS is one of the latest methods

addressing crosstalk issues that offers many advantages compared

to other existing methods. Novel Coplanar routing is an extension

of traditional microstrip routing that offers twice the routing

density compared to CHS microstrip routing. Besides that,

bandwidth per density will double if the Novel Coplanar routing

is applied to CHS 3D Novel routing.

Index Terms— Novel Coplanar routing; Crosstalk; Crosstalk

Harnessed Signaling; 3D Novel routing.

I. INTRODUCTION

In modern technology, the volume of smart phones and

tablets have increased rapidly reflecting higher demands on

internet usage in daily life. But the system needs to scale up and

there are design challenges to be overcome. Electrical signals

will suffer degradation as data rates increase in a densely routed

environment. One of the bottlenecks to system design

bandwidth is crosstalk noise. Thus, mitigating crosstalk helps

to improve the bandwidth demands.

There are multiple ways to mitigate the crosstalk such as

differential signaling, shielding or guard trace. These methods

are costly and inefficient for achieving high data rates

especially on high volume manufacturing(HWM). Besides that,

for differential signaling this requires twice signaling compared

to single ended and the guard trace method due to introducing

extra signals that will increase the board dimensions. Crosstalk

equalizer and eigen-mode signaling based on the modal

decomposition method is a new way to mitigate the

[2],[3],[4],[5]. These two concepts are promising for achieve

dense routing and higher bandwidth, but are very costly and

complex to design. In addition, this requires prior knowledge of

the channel characteristics and have complex termination

schemes.

Crosstalk Harnessed Signaling promises to be a method that

will improve on the modal decomposition and modal

composition schemes. This method was developed through

collaborative research between the University of South

Carolina and Intel. It offers lower cost, simple design, no

complex termination and no training is required on the channel.

This means that one static matrix works for different routing

types. Compared to other crosstalk mitigation schemes, a

different matrix is required for different routing schemes.

However, CHS shows it still works on CHS 3D Novel and

Novel Coplanar routing, which is introduced in this paper.

These two-routing schemes help to offer higher bandwidth per

volume.

II. CROSSTALK HARNESSED SIGNALING

Crosstalk Harnessed signaling (CHS) is a new technique for

mitigating crosstalk that offers better benefits compared to the

modal decomposition and modal composition methods. In this

paper, we will introduce the basic CHS method and then focus

on the CHS application in a new routing scheme. This technique

harnesses the crosstalk instead of eliminating it, thus

differentiating it from other crosstalk schemes. CHS offers

many benefits without requiring a complex transmitter (TX)

and receiver (RX) circuit design, nor complex termination. In

addition, no prior knowledge is required of the channel since

one CHS static matrix works for N channel lines.

Fig. 1 shows the CHS bus diagram [1],

Fig. 1 Crosstalk Harnessed Signaling (CHS) Block diagram

As shown in the figure, the encoder is placed after the

transmitter(TX) circuit and the decoder block is placed at the

end of the channel before the receiver(RX) circuit. The binary

input data is encoded and there are four levels of signals at Q.

In this analysis, 1024 bits have been simulated. 𝑉𝑄 is the

encoded multi-level voltage steps at node Q. [1]

𝑉𝑄 = 𝑉𝑏𝑖𝑡𝑊 (1)

The encoded signals propagate through the channel to node R.

The CHS encoding static matrix, W, spreads each binary across

the line N with specific properties. Thus, the noise that is

coupled from aggressor to victim lines becomes a part of the

41

signals. Then, the data arriving at node R is the encoded

channels at node Q convolved with the impulse response of the

channel. The signals are sampled and recovered at node S by

decoding circuit, 𝑉𝑠

Assuming 𝑉𝑄 = 𝑉𝑅 (with low channel loss and low-reflections),

𝑉𝑆 = 𝑉𝑅𝑊−1 (2)

III. TRADITIONAL ROUTING AND CHS 3D NOVEL ROUTING

The CHS concept has been proved on microstrip routing.

Simulations correlate well with validation [1]. Fig. 2 shows the

eye diagram for a 4-coupled microstrip transmission line having

4-mil spacing between the signal channels at a data rate of 8

Gbps.

Fig. 2 Four-coupled microstrip and eye diagrams with 4 mil trace spacing, six-

inch trace length at 8 Gbps data rate. Binary Traditional Signaling (Red), CHS

(Blue)

Binary traditional signaling requires more than 16 mil spacing

between signals in order to have a good eye opening as

illustrated in Fig. 3. Besides that, CHS is 2.5X faster than binary

signaling and the routing is 2.3X denser [1].

Fig. 3 Comparison between Traditional Binary Signaling (Red) and CHS at

different trace spacing at 8 Gbps

This research has been conducted on stripline routing and CHS

3D Novel routing to investigate the sensitivity of CHS

technique. Both routings schemes show that the CHS concept

is still valid and has advantages compared to traditional binary

signaling. Based on this analysis, CHS can support up to 1 mil

spacing at a conventional dielectric height. By introducing

Novel Coplanar Routing to CHS microstrip routing (~2.3X

compared to traditional binary signaling) and CHS 3D Novel

Routing (~10X compared to traditional binary signaling) the

routing density will double.

However in the CHS concept, conductor one shows eye

degradation for nibble-to-nibble analysis due to common-mode

signaling that is susceptible to the ground return path. In

addition, the first column of the CHS static matrix is associated

with an orthonormal positive vector value [1].

𝐖 = [

1 1 1 1−1 −1 1 11 −1 −1 11 −1 1 −1

] (3)

𝐖−1 = 𝐖𝐓 = [

𝑊11 𝑊21 𝑊31 𝑊41

𝑊12 𝑊22 𝑊32 𝑊42

𝑊13 𝑊23 𝑊33 𝑊43

𝑊14 𝑊24 𝑊34 𝑊44

] (4)

For conductor one, the common-mode noise is additive thus

causing the eye closure. However, for the other conductors most

of the noise is cancelled due to their differential nature. The eye

closure in conductor one is solvable by placing a ground trace

between nibbles or with isolated spacing between nibbles.

Conductor two to conductor four is somewhat “differential in

nature” that will help to improve signal-to-noise ratio by being

“self-referenced” [1]. Thus, eliminating the reference planes

will result in gains to the bandwidth per volume. Note, the

ground planes and power planes that are required for power and

signal integrity have been ignored in this analysis. This

requirement will be included in future research.

IV. NOVEL COPLANAR ROUTING

The new routing scheme that is based on microstrip routing

by eliminating the reference layer and placing the ground

conductor in the signals layer is illustrated in Fig. 4. This new

routing scheme is called “Novel Coplanar Routing”.

Fig. 4 Microstrip routing with reference plane elimination, “Novel Coplanar

Strips”

The electric fields and magnetic fields are shown in the sketches

below for the even-mode and odd-mode configurations between

microstrip and novel coplanar routing. They show different

field distributions between this routing scheme. The traditional

crosstalk is higher on the Novel Coplanar strip compared to the

microstrip routing as shown in Fig. 6 since the fields are

concentrated partially in air. However, for the Novel Coplanar

strip, crosstalk can be reduced by having tight coupling with the

reference signal since the electric field dispersed in the air

42

degrades travelling through different media that close to a

homogenous structure.

Fig. 5 Artist’s concept for electric and magnetic field intensity lines comparison

between Microstrip and Novel Coplanar Strips

Fig. 6 Far end crosstalk comparison between Microstrip, Novel Coplanar Strip

in frequency domain based on two-couple transmission line

The following is an analysis based on Fig. 4 routing. In this

routing scheme, we will expect different impedance values

between traces. Conductor one and four will have lower

impedance values while conductor two and three will have

higher impedances since they are farther from a reference plane.

For a six-inch transmission line, the eye diagram shows

degradation on conductor three compared with a three-inch

channel. This is due to a termination mismatch between signals

that produces more reflection and skew. Based on the CHS 3D

Novel routing approach, this can be solved either by reducing

the channel length or by impedance matching on the routing

scheme.

(a) Three-inch channel length (b) Six-inch channel length Fig. 7 Eye diagram based on Fig. 4 at 8 Gbps data rate (Red- Traditional Binary

Signaling, Blue – CHS)

The eye closing at conductor one is expected due to common-

mode noise that was introduced in the CHS matrix. A reference

signal has been added between signals to solve the reflection,

skew and common-mode issues as illustrated in Fig. 8. This

routing scheme has a symmetrical configuration compared to

Fig. 4 which is an asymmetric configuration. The routing is

close to microstrip routing but offering better density since the

number of layers for the stackup is reduced. The eye diagram

on Fig. 9 shows a better eye opening compared to Fig. 7. In

addition, there is an insignificant impact on the eye opening on

the ten-inch channel length.

Fig. 8 Alternative Novel Coplanar Routing for symmetric configuration

(a) six-inch channel length (b) ten-inch channel length

Fig. 9 Eye diagram at 8 Gbps based on Fig.8 configuration. (Red-Traditional

Binary Signaling, Blue- CHS)

Based on existing research, the common-mode noise will

increase at conductor one in a nibble-to-nibble configuration.

However, with symmetric Novel Coplanar routing the issue is

eliminated based on the edgeside and broadside routing scheme

as illustrated in Fig. 10.

Fig. 10 Novel Coplanar Routing for nibble-to-nibble configurations

This configuration provides a better Return on Technology

Investment (ROTI) compared to traditional routing that will be

shown in the next research paper. Good eye opening has been

observed based on Fig.10 edge-side nibble-to-nibble

configuration as illustrated in Fig. 11 with 2 mil spacing

between signals.

43

Fig. 11 Eye diagram for edgeside nibble-to-nibble configuration at 8 Gbps data rate, ten-inch channel length and 2 mil trace spacing. (Red- Traditional Binary

Signaling, Blue-CHS)

Based on the above analysis, the concept can be extended to

stripline routing as shown in Fig. 12, which demonstrates that

this concept is feasible for this analysis except that the reference

signals need to be added between the common-mode signals.

The stripline configuration shows less crosstalk since the fields

will fringe in the substrate area, which is close to a

homogeneous configuration. In the Novel Coplanar routing

scheme, termination is not an issue and length mismatch can be

supported for up to 100 mils between the signal traces.

Fig. 12 Coplanar Strip approach on stripline nibble-to-nibble routing

In existing research, CHS shows the capability to support the

CHS 3D Novel routing scheme, and can potentially grow an

infinite n number of nibbles vertically or horizontally. There is

the potential that the Novel Coplanar Routing concept can be

applied to 3D CHS Novel routing by eliminating the reference

layer and thus achieving 2X higher bandwidth per volume.

V. CONCLUSION

The CHS concept paves the way for introducing new routing

schemes that will offer higher bandwidth per volume compared

to traditional routing with no design changes required on the

CHS scheme. This paper shows that with this new routing

scheme, the routing density about doubles compared to CHS 3D

Novel routing and CHS microstrip routing. Traditional routing

is not recommended for high speed designs due to high

crosstalk from reflection, and the existing crosstalk solution

does not help reduce the routing density compared to the CHS

method. Nevertheless, this novel routing scheme is relatively

new and further investigation is required to understand the

advantages and sensitivity of the CHS concept. In addition,

proofs of concept need to be conducted in the future. Besides

that, Return on Technology Investment (ROTI) is a new

concept that will be discussed in the next research paper, which

will include the advantages of new routing schemes such as

Novel Coplanar and CHS 3D Novel routing compared to

traditional routing.

ACKNOWLEDGMENT

Special thanks to Professor Dr. Paul G. Huray the author of

the books, Maxwell’s Equations and The Foundations of Signal

Integrity, Dr. Femi Oluwafemi, Stephen H. Hall from Intel,

USA and Tom McDonough from USC for their valuable

guidance throughout this research.

REFERENCES

[1] C. Sreerama, “Novel crosstalk mitigation solutions for high-speed

interconnects to maximize bus band-width and density,” 8th annual signal

integrity symposium, Penn State Harrisburg, PA, Apr. 4, 2014, pp. 1. [2] F. Broyde and E. Clavelier, “A new method for the reduction of crosstalk

and echo in multiconductor interconnections,” IEEE Trans. Circuits Syst.

I, Reg. Papers, Vol. 52, pp. 405-416, Feb. 2005. [3] C. R. Paul, “Analysis of multiconductor transmission lines,” 2nd ed., New

York, NY, Wiley-Interscience, 2007.

[4] S. H. Hall, H. L. Heck, “Advanced signal integrity for high-speed digital designs,” 1st ed., Hoboken, NJ, Wiley-IEEE Press, 2009.

[5] C. Yongjin, H. Braunisch, K. Aygun, and P. D. Franzon, “Analysis of

inter-bundle crosstalk in multimode signaling for high-density interconnects,” ECTC, Lake Buena Vista, FL, 2008, pp. 664-668.

Azniza Abd Aziz received her PhD. In electrical engineering

(signal integrity) from University of South Carolina. Her

current research interest includes Signal Integrity solutions for

high-speed data design. She was an Advanced Signal Integrity

Engineer in Intel, Penang, Malaysia and Senior Signal Integrity

Engineer in Hewlett Packard Enterprise, California, USA with

almost 10 years experiences working on designing, validation

desktop, mobile and server platforms. Currently, she is lecturer

at USM, Malaysia.

Chaitanya Sreerama is a staff hardware engineer at Intel Labs

in Hillsboro, OR. She received her B.S degree in electronics and

communication engineering form JNTU, India in 2001, M.S

degree in electrical engineering (numerical & computational

electromagnetics) from Clemson University in 2004, and PhD.

degree in electrical engineering (signal integrity) from

University of South Carolina in 2014. She has been working at

Intel since 2004, and her areas of expertise include EMI, RFI,

and Signal Integrity. In addition to patents (14) and publications

(4), she has been awarded the 2010 Intel Achievement Award

for her contributions to the company.

44

A Grounded Capacitance Multiplier Based on CCII

J. Vavra Univ. of Defence, Dept. of Electrical Engineering, Kounicova 65, 662 10 Brno, Czech Republic

jiri.vavra@unob.cz

Abstract—The capacitance multiplier is an active block which

emulates the synthetic passive capacitor, whose capacitance is

several times bigger than the reference real capacitance used in

circuit connection. Multipliers are used in the design of

integrated circuits for the realization of high-value on-chip

capacitances. The paper describes one possible way of

multiplying the capacitance with a minimum number of active

and passive components. The proposed circuit uses only one

active element, the second-generation current conveyor (CCII),

and only one grounded passive component – the reference

capacitor, whose capacitance is being multiplied. This idea

connects the circuit theory and microelectronic approach because

capacitance multipliers are using in the design of integrated

circuit area, where the capacitance multiplier can save valuable

space on the chip. For test reasons, the active element is

composed of commercial amplifiers and the verification is

ensured by experimental measurement on the prototype and by

SPICE simulations.

Index Terms— Capacitance Multiplier, Current Conveyor,

Howland current pump, current mode.

I. INTRODUCTION

The capacitor is one of the basic components of analog

integrated circuits, significantly contributing to the accuracy in

design functionality. The implementation capacitors on the

chip require a large area, especially if the capacitor value must

be as big as possible, like the so-called Zero Making Capacity

in Phase Locked Loop constructions [1]. Moreover, the

fabrication of low-noise capacitors of the same dimensions

(CMOS image sensor) brings further technological

complications not only because of limited space on the chip

[2]. Thus the Capacitance Multipliers (CM) play a very

important role in the area of integrated circuits because they

reduce the requirement for die area because they emulate a

larger capacitance using a much smaller capacitor. In the

0.18μm technology, the MIP capacitors (metal-insolator-

polysilicon) [3] require a typical value of 500 μm2/pF. Taking

into account the high absolute tolerance (±20% in the same

technology), correction mechanisms such as trimming are

often required, leading to an even larger circuit area.

There are two different approaches in the CM design, the

voltage and the current approach. The voltage-mode

capacitance multiplier uses the Miller effect [4-6] through

which a high multiplication factor can be achieved but the

circuit is limited to low-frequency operation and low dynamic

range. The current-mode multipliers add a scaled copy of the

current flowing through a reference capacitor to the driving

circuit, simulating a higher total load current, while

maintaining the load impedance's capacitive nature. This is

equivalent to a larger load capacitance.

Recently many proposals of capacitance multipliers using

active building blocks have been reported. Several of them use

as the active building block the second-generation current

conveyor (CCII) [8-12] or other active elements [13-20].

Many of the proposed ideas fail in one or more of the

following aspects: use of two or more active elements,

excessive employment of passive components and floating

passive components or impossibility of tunability.

The main idea of the paper is a maximum simplification of

CM. The paper offers a simple circuit idea of CM with only

one CCII and one grounded working capacitor. This means

one buffer and one current-controlled current source. The

multiplication can be provided by using an input voltage

amplifier or by amplifying the controlled current source (the

ratio of transistors in the current mirror).

II. SECOND-GENERATION CURRENT CONVEYOR (CCII)

CCII is a well-known and often used active building block

which was introduced by Sedra and Smith in 1970 [21]. Fig. 1

(a) shows its schematic symbol and Fig. 1 (b) its

corresponding behavior model.

Figure 1: Schematic symbol and behavioral model of CCII-.

There are two versions of CCII – inverting and

noninverting, which are labeled CCII+ and CCII- respectively,

depending on the direction of output current Iz. In this paper,

the proposed CM uses the CCII- type.

The voltage signal Vy, which is connected to the input

terminal y, is buffered into the low-impedance input x. The

current flowing into the terminal x as current Ix is conveyed to

the high-impedance output z as the output current Iz flowing

into the terminal z (CCII+) or out from the terminal z (CCII-).

The ideal behavior of the CCII- can be described according to

Fig. 1 by a system of equations (1) as follows:

45

1 0 0

0 0 0

0 1 0

x y

y x

z z

V V

I I

I V

=

. (1)

III. PROPOSED CIRCUIT

The proposed CM circuit based on CCII- is shown in Fig. 2;

it is one of the easiest versions of CMs. The ideal function of

CCII does not allow multiplication, because Vx = Vy and Iz = Ix,

so the multiplication factor is 1 – in the ideal case. But if the

CMs are mainly designed for integrated circuit application, the

construction of current mirror or voltage buffer allows

introducing the multiplication coefficients Ab and/or Ac during

the matching. Referring to this idea, Fig. 2, and using (1) the

corresponding flow graph can be calculated as shown in Fig.

3, where the variables Ab and Ac are the gain of input buffer

from Vy to Vx and the gain of the current mirror from Ix to Iz,

respectively. In the common case, these variables are equal to

1, but this can be changed during the preparation of the final

layout.

Figure 2: Capacitance Multiplier based on CCII-.

Figure 3: Corresponding flow graph of proposed CM.

According to Mason’s rule, the input impedance of the

circuit can be derived as follows:

11

1

1

b c

VZ

I sCA A= = . (2)

The equivalent capacitance Ceq follows from (2) and is

given by the following multiplication:

eq b cC CA A= . (3)

The value of Ceq can be set by the value of voltage gain Ab

or by the value of current gain Ac.

Because of the limited dynamic range, the current multiplier

is more suitable than voltage gain.

IV. ANALYSIS OF REAL EFFECTS

In addition to the ideal parameters, each active element

represents some real features which affect the ideal behavior

of the whole circuit. Some of them can play an important role

in interesting frequency range, dynamic range, or in linearity,

i.e. primarily parasitic impedances of each terminal, finite

voltage tracking error b from the high impedance input

terminal y to the low impedance terminal x and finite current

tracking error c from this terminal x to the high impedance

output terminal z. The frequency dependence of voltage and

current gains is not considered because of their application in

the higher frequency range. The final layout of the chip must

be modified so that these effects will not affect the function of

the application. In Fig. 4, all the parasitic influences

considered are shown in red.

Figure 4: Proposed CM with considered parasitic influences of the CCII-.

The parasitic impedances of the terminals y and z work in

parallel connection, thus they can be connected to one pair of

impedances Ryz = Ry || Rz and Cyz = Cy + Cz.

The modified signal flow graph respecting the real effects is

given in Fig. 5:

Figure 5: Signal flow graph of proposed CM with real influences of the CCII-.

The calculation of the overall impedance is routed to a

complicated model composed of an FDNR (Frequency

Dependent Negative Resistor), an inductor, two capacitors and

two resistors. This calculation can be simplified by separating

the coupled impedances Cyz and Ryz, which are connected

directly to the input terminal. The calculation is then very

simple because it is composed of voltage and current gains Ab,

Ac and their real deviations b c multiplied by a serial

46

connection of the parasitic resistor Rx and the reference

capacitor C. This is suggested by the straight line of the signal

flow graph in Fig. 5.

The input admittance of the circuit in Fig. 4 can be written

as follows:

1

b b c cyz yz

x

sCA AY G sC

sCR

= + +

+.

(4)

Equation (4) implies that the admittance Y is made by a

parallel connection of the coupled impedances Cyz and Ryz and

a serial connection of the resistor Rx and the working reference

capacitor C multiplied by the gain variables Ab, Ac and their

real deviations b c. The final equivalent impedance model of

the proposed CM with the parasitic influences considered is

shown in Fig. 6:

Figure 6: Impedance model of proposed CM based on CCII.

where the values of components Cs and Rs are given by the

equations:

s b b c cC CA A = , xs

b b c c

RR

A A = .

(5)

Considering that all the parasitic influences are in their ideal

values (Rx = 0 Ω, Ryz = ∞ Ω, Cyz = 0 F, b = c = 1), then the

resistance Rs equals 0 and the capacitance Cs equals Ceq in

equation (3).

V. CCII IMPLEMENTATION

As mentioned in the Introduction, the CM is most useful in

the area of integrated circuits, where the realization of real

capacitances is quite expensive because of their size on the

chip. For a better verification of the proposed circuit, the

implementation of CCII is required. It must be clear that the

simulation results presented are limited by the real behavior of

integrated circuits. It can be assumed that the on-chip

realization of CCII will generally have better properties,

depending on the CMOS technology used and on matching.

Figure 7: Conception of the CM based on CCII-.

For verification reasons, an interesting implementation of

CCII [22] can be used. One approach, based on the

well-known Howland current pump, is presented in [23]. The

final proposed circuit of CM with the Howland current pump

as a CCII is shown in Fig. 7.

Because of the negative feedback of OA1, the voltage on the

working capacitor C precisely follows the input voltage V1,

which is the first basic feature of CCII. The current flowing

through the reference capacitor is forced to flow through the

first sensing resistor RS1. The instrumentation amplifier IA1

senses the voltage drop at this resistor, whose output voltage is

given by the sum of this voltage drop and the voltage level at

the ref terminal. The voltage at the ref terminal is a buffered

copy of the input voltage V1, thus the voltage drop at the

resistor RS2 is only given by the voltage drop at the resistor

RS1, which is sensed by IA1. The result is the input current I1,

which is formed by the current flowing through the reference

capacitor multiplied by the ratio of the sensing resistors RS1

and RS2 assuming the unity gain of IA1 – if RG is omitted:

1

2

Sc

S

RA

R= .

(6)

In Section III, the possibility of tuning the gain

(multiplication factor of CM) is presented. In the

implementation presented, two possible ways of changing the

gain are available. The voltage gain Ab can be changed by

adjusting a higher gain of the instrumentation amplifier IA1.

Thus the RG must be added, otherwise the unit gain of the

instrumentation operating amplifier IA1 is preset. Another

possible way to increase the gain is by changing the ratio of

resistors RS1 and RS2. It can be considered as a current gain Ac.

VI. PRINCIPLE VERIFICATION

For a concrete example, the working capacitance can be

selected C = 1 nF and the multiplication coefficient can be 10

(Ab = 1, Ac = 10). According to (6), the resistor RS1 = 10RS2.

With respect to the limited dynamic range, which is affected

by the value of RS1, the values of these resistors are selected as

follows: RS1 = 33 kΩ and RS2 = 3.3 kΩ. All the amplifiers in

the proposed circuit were selected with respect to giving

preference to accuracy, low power consumption, and low

offset. The precision instrumentation amplifier AD8226 [24]

was selected as IA1. The zero drift CMOS operational

47

amplifiers OPA735 [25] were selected as both operating

amplifiers OA1 and OA2. All active devices were supplied by

±5 V. The amplifiers AD8226 and OPA735 provide low offset

voltage (50 V and 5 V) with low drift (0.5 μV/°C and 0.05

μV/°C). The input differential impedance of the AD8226 is

800 M with a parasitic capacitance of 2 pF, thus it does not

degrade the output resistance of the CCII. The low input bias

current (200 pA) of the OPA735-based voltage buffers

represents a negligible error in setting the output current.

The parameters of the final equivalent circuit in Fig. 6 can

be obtained from a detailed analysis of the Howland current

pump, as is done in [26]. According to this analysis, these

parameters are as follows: Cyz = 4 pF, Ryz = 800 kΩ,

Rs = 0.01 Ω, Cs = 9.99 nF according to (5) and for

low-frequency signals.

For a verification of the proposed circuit, the RC circuit in

series connection was selected. The CM was connected to the

input signal VIN = 1V/10kHz through the resistor R = 1 kΩ.

The operation of CM was tested via transient analysis and

measured on a sample which was assembled using

components as mentioned above. The results of measurement

and the SPICE transient analysis of the proposed RC circuit

for 1 V/10 kHz sinusoidal excitation are shown in Fig. 8. The

ideal waveform is the same as a simulated response. As is

clear from Fig. 8, the amplitude of the measured current

response flowing through the real CM is practically the same

as the current response flowing through an ideal capacitor with

a capacitance of 10 nF and simulated CM. The small visible

deviations are caused by the parasitic resistor Rs.

Figure 8: Measured waveform (I1M) of proposed RC circuit with CM for

1 V/10 kHz sinusoidal excitation in comparison with simulated (I1S) and ideal (I1I) current response.

VII. CONCLUSION

The paper describes the utilization of capacitance

multipliers in a microelectronic area. The capacity of

grounded reference capacitance is transformed to a higher

value by using only one basic active element and one

grounded capacitor. This transformation saves expensive

space on the chip. Disadvantages of this transformation are the

implementation of parasitic impedances and frequency

limitations which are hidden in the active element. The

analysis points out the possibility of eliminating some

parasitic influences, especially in terms of mere changes of the

cutoff frequency.

The proposed capacitance multiplier was analyzed for real

effects, measured on the real specimen and simulated via the

SPICE transient analysis. The measured and simulation results

are in good agreement with the behavior of ideal CM.

ACKNOWLEDGMENT

This work was supported by the Project for the development

of K217 Department, University of Defence Brno.

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49

An Overview of Information Hiding

Techniques; Challenges and Applications

A. Omar Adil Deheyab1, 2, B. B Rahmatullah22 and C. M. Hashim33

1Universiti Pendidikan Sultan Idris , Malysia. Corresponding author: First A. Author (e-mail: oad888@yahoo.com).

Abstract ; Currently, many people communicate with

each other over the Internet, however, information

transmission is not very secure, where there is a high

probability for copying and altering the information

easily. Transmitting the sensitive or private information

needs some kind of protection especially in the public

network unless a secure channel is utilized for the

transmission. Information hiding is one of efficient

technique that provides solution to the problem of

transmitting important data over communication

channels. These techniques should meet various

applications requirements such as high robustness

against attacks, real-time, and high hiding capacity.

Generally, information hiding techniques suffer from

many challenges. This paper seeks to provide an insight

of these techniques, their applications and challenges to

fill the gap of missing such overview.

Keywords: Information hiding; Steganography;

Cryptography; Watermarking

1. Introduction

The Internet is an open network so it is easy to obtain

and transmit all kinds of multimedia information like

audio, video and images freely, which brings many

threats to information security such as piracy, theft,

and ownership issues [47] . Several methods have

been utilized to protect sensitive and critical

information during their storage or transmission.

They mainly depend on cryptography or information

hiding techniques (also called data hiding) [3].

Information hiding is the art of embedding

information inside another medium during

transmission. The information is embedded into a

cover medium (image, audio, video, or text) to create

the embedded medium (in watermarking applications

is called watermarked object, while in steganographic

applications is called a stego object) [14]. The

information hiding scheme requires visual quality of

embedded images, hiding capacity (called payload),

and robustness. The scheme with low image

distortion is more secure than that of high distortion

because it does not raise the attackers’ suspicions.

The scheme with a high payload is preferred because

it assists to transmit more secret data. The robustness

is mainly significant but achieving robustness is

technically challenging in high-payload data hiding

scheme. Generally, visual quality, hiding capacity,

and robustness are conflicting issues; therefore, a

tradeoff among them is desirable. However, the

tradeoff differs from application to application,

depending on users’ requirements and application

domains [14]. Information hiding techniques can be

divided into irreversible and reversible information

hiding. If a data-embedding scheme is irreversible

(also called lossy), then the secret data only can be

extracted and the original cover image cannot be

restored. On the other hand, a reversible (also called

invertible, lossless, or distortion-free) data-

embedding scheme allows recovering the original

cover image completely upon secret data extraction.

This technique plays a vital role in many

applications, such as military and medical images

[14,46, 34] . Information hiding techniques (called

information hiding or information embedding) can be

categorized into two types: steganography and

watermarking according to the applications that

information hiding is utilized for [48, 3].

Cryptography is considered as a hiding technique. It

can be interwoven with steganography and

watermarking. The goal of cryptography and

steganography is to conceal the data, but their

implementation methodologies are varied. The

watermarking and steganography methodology is

same, but their goals are varied. Watermarking

concerned with digital data copyright protection,

while steganography deals with digital information

hiding[5].

2. Steganography

Steganography is a term derived from the Greek

word steganos which means covered or secret and

graphie that means writing or drawing i.e., covered

writing [2,10]. Steganography refers to hide

50

information in a cover medium without changing its

original quality to prevent its detection from

unauthorized attempts which makes it a main choice

for secret communication [12,45,2]. In other way,

steganography prevents the intruder from suspecting

the secret information in the cover object. The cover

medium (also called host or carrier) usually may be

any digital medium such as an image, audio, or video

file. However, images are widely used as a cover for

steganography because of its prevalence in daily

applications and high redundancy in representation

[27,35]. The hidden message (also called payload)

may be of any type such as text, image, audio, or

video [21,17]. The two important properties of

steganography are (i) good visual/statistical

imperceptibility of the payload which is essential for

security of hidden communication and (ii) payload is

essential to convey large quantity of secret

information. Steganography has to satisfy capability

and the transparency requirements. Capability means

embedding large payload into media. Transparency

indicates an ability to prevent distinctions between

stego and cover image by perceptual or statistical

analysis [38]. The security of a steganography system

increases if the payload remains unreadable to an

attacker even if he has knowledge about the

embedding method [35]. Steganography techniques

can be classified into two major categories such as

spatial domain techniques and transform (frequency)

domain techniques. In spatial domain techniques the

secret message is hidden inside the image by

applying some manipulation over the image various

pixels [45]. In transform domain techniques the

image is transformed to frequency domain and the

secret message is hidden in the coefficients [1].

Steganography methods in spatial domain include

LSB steganography, RGB based steganography, pixel

value differencing steganography, mapping based

steganography, palette based steganography, collage

based steganography, spread spectrum

steganography, code based steganography, and others

[45]. Steganography methods in transform domain

include DCT (Discrete Cosine Transfer), DWT

(Discrete Wavelet Transfer), and DFT (Discrete

Fourier Transfer) [40]. Spatial domain techniques

offer higher payload but are prone to various normal

attacks such as JPEG compression, noise attacks, and

low-pass/high-pass filtering and geometric attacks

such as image resizing, cropping and rotations by

different angles. Transform domain techniques

provide lower payload but can resist various attacks

[32].

2.1 Steganography Challenges

The major challenge in steganography is how to

produce stego images with high imperceptible, and

how to increase the amount of payload capacities in

the stego image [4]. The message must be hidden in

the cover image in such a way that the generated

stego-image does not deviate much from the original

image, visually and statistically [17]. Steganalysis is

devoted to defeat steganography and detect its

presence. Therefore, steganography must pay more

attention to the visual quality, the statistical

imperceptibility, the capacity of embedded data, and

the resistance against detection [48,31]. Visual

quality is a significant issue, in some applications

such as law enforcement, military image systems, and

medical diagnosis, where a small image distortion is

unacceptable [14].

Another significant challenge is the limited

embedding rate in the transform domain, and the

vulnerability of spatial domain to various attacks like

JPEG compression, high pass filtering, low pass

filtering, cropping etc [21,16,4]. There are many

steganography algorithms proposed by many

researchers, however, some of these algorithms are

very complicated due to the long time needed to hide

secret data such as DWT, while the others are simple

methods with low complexity as in LSB [4]. It is

worth mentioning that steganalysis tools development

degrades steganography schemes performance, thus

researchers should develop secure steganography

techniques to defeat attackers and steganalysis [31].

2.2 Steganography Applications

Steganography has different convenient applications.

The applications include copyright control of

materials, enhancing robustness of image search

engines and smart IDs (identity cards). Other

applications are video-audio synchronization,

companies’ safe circulation of secret data, TV

broadcasting, TCP/IP packets, medical imaging

[15].The steganography can also be used for secure

exchange of secret messages between sensitive

organizations, securing online banking, and voting

systems, nefarious use by attackers to send viruses

and Trojan horses, as well as secret communication

between terrorists and criminals [32].

3. Watermarking

The development of the computer and network

technology facilitates the production, distribution,

acquiring and copying digital media products such as

digital text, image, video and audio. Therefore, it is

mandatory to protect digital media copyright of the

media owner and consumer [28]. One of the effective

solutions is the digital signature, which can be

51

embedded in data by using watermarking. Digital

watermarking is an effective solution for copyrights

protection with the extensive productions of digital

multimedia in the information technology era [29].

Digital watermarking is one of the common methods

for authentication digital images. Digital

watermarking inserts a sign or logo into the cover

image that can confirm the originality of the image

after extraction [8]. Digital watermarking concept is

similar to steganography; they both hide a data inside

a digital media. However, the difference between

them is their goal. Watermarking hides a data related

to the actual content of the digital signal where both

data and digital signal are important, while

steganography has no relation between digital signal

and data. The digital signal used as a cover to hide

the data i.e. the data is mainly important only [26].

Hiding the watermark is not necessary for all

scenarios, and high capacity is also not necessary as

signatures are usually small. Generally, watermarking

protects digital data from copyright violation and

counterfeiting, by embedding a digital signature with

less distortion in the cover image. However, this

distortion is not acceptable in case of military and

medical images [14,47]. Moreover, watermarking

schemes are also desirable for protection of the

content and the integrity of images due to their ability

of recovery, as well as tamper detection [7]. The

watermarking can be visible or invisible. In visible

watermarking technique, human can perceive the

watermark, while in invisible watermarking

technique the watermark cannot be perceived by

human. The invisible watermark is established by

alteration made to the pixels that cannot be

perceptually noticed [19]. There are three basic

requirements for invisible watermarking. One of

them is that the distortion to the pixels of host image

(due to embedding of watermark) should be too small

to be noticed. The second requirement it should be

robust in case of various attacks, and finally high

security should be provided to the watermarking

scheme [30].

Watermarking technologies are categorized

according to implementation domain to spatial

domain or frequency (transfer) domain. In spatial

domain, data embedding is performed directly

through pixel modification, while in frequency

domain, data is embedded in the coefficient. The

transfer domain schemes are more computational

complexity comparing to the spatial domain but

provide better robustness than spatial domain

schemes with lesser payloads [43,9]. As the

watermarking is considered as an information hiding

technique, it can also be divided into irreversible and

reversible. The reversible watermarking scheme must

have the ability to recover the watermark even if the

watermarked image has undergone un-intentional

attacks [46]. Digital image watermarking generally

classified in three main groups Robust, Fragile and

semi-Fragile [33,7,19,8]. Robust watermark has the

ability to resist certain malicious attacks or general

image processing operations like cropping, filtering,

compression, etc. [50,51]. It is used for copyright

protection and finger printing applications. Fragile

watermarking is very sensitive to any changes to the

watermark image. It will be destroyed if its content is

slightly tampered. It is used for authentication and

tamper detection. Semi fragile watermarking has the

ability to endure some un-intentional changes such as

the lossy compression and channel noise but it is

fragile against malicious attack [16,42,40].

3.1 Watermarking Challenges

The robustness of digital watermarking schemes is

critical [14]. It is also critical to develop general

technique for all the digital media that is robust

against various attacks [16]. Generally, achieving the

watermark requirements in terms of imperceptibility,

robustness, and high capacity is necessary. However,

it is difficult to maintain balance between

imperceptibility, robustness and capacity [16]. Some

other challenges of watermark are identified as

follows [2]:

• It is destroyed if anyone manipulates the

image.

• The watermark may become unreadable due

to some operations like compressing,

resizing

• It protects the copy right but doesn’t prevent

copying of image. However, it can trace and

detect the copied image ownership.

Although watermarking is an easy tool to protect

ownership of data, but a lot of fraudulent cases are

reported [23].

3.2 Watermarking Applications

The watermark used as a significant tool in various

applications. Traditionally, watermarking has been

used to certify a document's authenticity for

passports, money and certificates, copyright

protection, document authentication, monitor

broadcast news stories, advertisements and internet

promotions [49]. In the following are different

applications for digital watermarking [43,25,31]

• Copyright Protection: to identify the image

source and its authorized user

52

• Data Authentication: Digital signature is a

common data authentication approach

• Fingerprint: increase the stiffness of the

image against alteration or elimination

• Copy Control: keep the security and control

during information distributing and

publishing

• Device Control: used to control access to the

resource using a verifying device

• Fingerprinting: carry the information about

legal recipients

• Tracking: track the users, identify illegal

content, track transactions

• Temper detection: reveal all the changes

which have been made. It is similar to

authentication

• Broadcast monitoring: broadcast the

conversation over some radio and television

• Completeness: detect the modification in

data. This is also an authentication

• Intellectual property protection

4. Cryptography

The term cryptography has come from the Greek

word “kryptós”, which means hidden and “gràphin”

which means “writing”. Therefore, the cryptography

meaning is “hidden writing [2,37]. Cryptography is

the protecting data process by changing it (plaintext)

into an unreadable format called cipher text. The

changing process of data to another format is called

encryption. Decryption is the process of recovering

the original data from the cipher text by using a

secret key. Cryptography is crucial to secure data

from illegitimate access by attaining their

confidentiality, authorization, non-repudiation,

integrity, and availability [17,44]. In cryptography,

the sensitive information is written in such a way that

only the intended recipient can recover it [20]. An

unauthorized party knows the existence of private

data, but his challenge is how to decipher the

encrypted data [17,20]. Cryptography scrambles and

disorganizes information in such a way it cannot be

recognized by attackers during storing and

transmitting. Modern cryptography is heavily based

on mathematical and computer science practice

[38,24]. The cryptography can be divided into

symmetric-key (Private key) cryptography and

asymmetric-key (Public key) cryptography. In

symmetric key cryptography, same key is used by the

sender and the recipient for encryption and

decryption, while in asymmetric key cryptography,

each sender and recipient use two keys, public key

for encryption and a private key for decryption. The

symmetric key cryptography is generally preferred

for large data such as image and video. Asymmetric

key cryptography has higher computation costs.

Examples of symmetric key cryptography are data

encryption standard (DES), triple DES, RC2, RC4

IDEA, AES, Blowfish and Skipjack. Examples of

asymmetric key algorithms are Diffie-Hellman, RSA

and Merkle-Hellman [6,39,40]. Symmetric

algorithms are much faster than asymmetric ones

[18]. The quality of encryption is tested by its

capability to defend different attacks like known

plaintext attack, cipher text only attack, statistical

attack, deferential attack, and brute-force attack, etc

[6]. Cryptography strength depends on the key size,

the more key size; the more expensive computing

power is required to decrypt cipher text [37].

4.1 Cryptography Challenges

Despite outstanding functionalities and security

pledge of cryptography techniques, utilizing

cryptography to provide effective security in practice

is a challenge. Practical settings regularly raise

threats that are not sufficiently reflected by traditional

security modeling of cryptographic [36]. The most

secure cryptographic systems can be rendered fully

insecure by a single specification or programming

error [11]. Although cryptography algorithms are

very useful, it is also breakable. Encrypted data can

sometimes be broken by cryptanalysis, also called

code breaking [44]. All cryptographic based

algorithms have some advantages and disadvantages

related to time and security problems [39]. For

example, traditional symmetric algorithms, such as

DES, AES, and Blowfish require more time, storage

and mathematical computation [13]. Cryptographic

algorithms are cost and computation power intensive.

For example, asymmetric ciphers are computationally

needs more hardware and software [18]. Generally,

cryptographic methods Limitations include 1) it takes

a long time to detect the code 2) huge computational

complexity, 3) cipher form attracts the attackers’

attention, resulting in modification or decryption of

secret data [10,31]. However, cryptography can

prevent the unauthorized access to the important data,

but it cannot prevent the legal person from copying

the decrypted data [25] . Last but certainly not least

while cryptography is very powerful for securing

data; the cryptanalysts could success to break the

ciphers by analyzing the contents of cipher text to get

back the plaintext.

4.2 Cryptography Applications

Cryptography is very significant to provide security

against statistical attacks and other types of attacks

53

when data are exchanged between two parties on a

network [44]. Therefore, it is used for security

purposes in wide applications including [22]:

• Governments’ applications such as

diplomatic missives, military purposes, army

plans.

• Industrial applications such as mobile,

Internet, wireless communication, e-

commerce applications

• Data applications, such as electronic mail,

electronic data interchange (EDI), transfer of

Domain Name System (DNS) and routing

information, electronic forms, and digitally

signed documents, information security

• Financial applications such as payments,

electronic checks, and online banking

5. Conclusion

To protect sensitive and confidential data from illegal

access and illegitimate use during their storage or

transmission through public network like the Internet,

several protection techniques are used such as

steganography, watermarking, and cryptography.

Even these techniques are important and necessary

for various and wide applications, they suffer from

some challenges that affect their performance. This

paper introduces an overview on these techniques and

reviews some of their significant challenges. The

paper also presents different applications for of these

techniques, which are significant to various research

works.

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55

Virtual Rehabilitation System for Carpal Tunnel

Syndrome Through Spherical Robots

Jorge S. Sánchez, Jessica S. Ortiz, Paola M. Velasco, Washington X. Quevedo, Daniel Castillo-Carrión,

Aldrin Acosta F, Julio Tapia, Cesar A. Naranjo, Franklin M. Silva M and Víctor H. Andaluz Universidad de las Fuerzas Armadas ESPE, Sangolquí-Ecuador

jssanchez, jsortiz4, pmvelasco1, wxquevedo, dacastillo, gaacosta, jctapia3,canaranjo, fmsilva, vhandaluz1@espe.edu.ec

Abstract—This article presents the development and

implementation of a virtual tool for performing rehabilitation

exercises in persons that suffer from the carpal tunnel syndrome,

using robots (Sphero - Ollie) as haptic devices. This tool presents

different scenarios with interactive games, in which you can

perform the rehabilitation movements of the wrist of the hand,

these movements are registered by the robots, the same ones that

transmit the data of speed, position and signals of correction of

the exercises realized to the platform of virtual reality, in order to

obtain the evolution of the same. The results show the favorable

acceptance of the use of this tool as an alternative for carrying

out rehabilitation exercises in people suffering from carpal tunnel

syndrome.

Index Terms— Virtual Reality, Teaching methods, Carpal

tunnel syndrome, Rehabilitation.

I. INTRODUCTION

The study of cumulative trauma disorders that occur in

work environments as part of work routines and activities has

been a constant topic of analysis [1]. The main reasons for

disability and early retirement are caused by musculoskeletal

disorders that are produced in work environments, this type of

injuries mainly affect the muscles, tendons, nerves and blood

vessels, and that produce a great variety of physical disorders

such as contractures, strains, fiber breakage among others [2-

3], one of the most common is carpal tunnel syndrome.

Carpal tunnel syndrome, CTS, is considered a neuropathy

with a prevalence of 3% to 6% of the adult population [4];

similar studies show that unnatural postures when making

violent and irregular movements like lifting heavy loads, cause

negative effects on health, or they are also motivated by the

repetitiveness of movements and body contractions product of

forced postures when executing a certain task [5]. The Carpal

Tunnel Syndrome is a disease that originates inside the tunnel

formed by the carpus and the transverse carpal ligament

located in the wrist, as a consequence of the pressure under the

various tendons and the median nerve found there, causing

inflammation with pain, weakness and burning in the hands

and fingers, as well as tingling with numbness of the fingers.

[4], [6-7]

Treatments to this ailment, begin to make modifications in

their work routines in order that, while they perform their

work, your wrist remains in a neutral position (with the wrist

joint straight and not down), and that depending on the degree

of ailment the specialist doctor can include the application of a

splint that is used at night, anti-inflammatory medications

(corticosteroids) that relieve pain and numbness; however, if

your CTS symptoms are severe or do not improve with the

treatments mentioned, surgery should be used to free the

carpal tunnel and eliminate the pressure exerted on the median

nerve [8].

Currently, with the advance of science and technology, new

alternatives are being analyzed to heal this type of ailment.

The National Institute of Neurological Disorders and Stroke

(NINDS) is the main sponsor of the federal government of

biomedical research in neuropathy using technology as:

transcutaneous electrical stimulation, ultrasound, biofeedback,

orthosis, that have been used with patients who have CTS and

that its application has been effective [9]. Emerging

technologies such as Virtual Reality, VR, are beginning to be

applied in this type of disorders, allow to develop different

interactive scenarios capable of creating a simulation that

involves all the senses, in real time in the form of digital

images and sounds, giving the sensation of presence in this

virtual environment [6], [10-11]; there are applications that are

already being applied as is the case of the Mobile Mixed

Reality System (MoMiReS): a 3D game based on smartphones

that generates physical interactions with a wireless glove that

lead to a set of repetitive movements to rehabilitate problems

originated in the wrist of the hand, with games specifically for

the treatment of CTS, achieving high system approval ratings

[12-13].

In this context, the article proposes the development of a

virtual tool, in which interactive games are implemented in

which the rehabilitation exercises are allowed, for the CTS,

using robots that allow interaction in the proposed games with

the aim of completing rehabilitation to reduce the discomfort

caused by this syndrome.

This article is divided into 6 Sections including the

Introduction and References. Section 2 present the Problem

formulation, in which the traditional rehabilitation exercises

are described in a fast way; describes of the development of

the proposal in Section 3; in section 4 the usability analysis of

the proposed tool is presented and finally the conclusions are

detailed in Section 5.

II. PROBLEM FORMULATION

The CTS are considered as an occupational disease, some

56

authors [14] consider that the etiology of the CTS is largely

structural, genetic and biological, and that environmental and

occupational factors, such as the repetitive use of the hand,

generate this syndrome. Some of the work factors that have

been better related to the development of STC are those that

cause an increase in pressure in the carpal tunnel due to

inadequate estimation of the load on the hands. Examples of

tasks related to the STC stand out the specific position of the

hand during the performance of the task (dorsiflexion flexion,

extension and substitute), the resistance to overcome with the

fingers the grip and possession of an object, the pressure on

the hand, the repetitive movements and the work with

vibratory tools. These factors are frequently observed in the

work of people employed in meat processing, assembly of

sub-assemblies, packaging of products, or employees such as

supermarket cashiers and people who work with computers. Among the traditional exercises used as therapy to reduce the CTS are: i) Extend and stretch the wrists and fingers out, ii) Stretch both wrists forward and relax the fingers, iii) Make a frozen fist and turn to the left and iv) With your fist frozen, gently bend each wrist down. [15]

Figure 1. Extension and Stretching Exercises

Many of the traditional rehabilitation exercises can be performed on an individual basis, so that people suffering from this syndrome lose interest in carrying out rehabilitation exercises in a continuous manner, not complying with the time of the rehabilitation period indicated.

For the above, we propose a virtual tool that helps to

perform the rehabilitation exercises in a different way, through

interactive games in which these exercises can be done in an

entertaining way using robots as haptic devices that help in

carrying out the exercises and allow to record the speeds and

scopes of the movements, with which you can generate

historical evolution of the realization of them

III. PROPOSAL DESCRIPTION

The bilateral interaction between the patient and the virtual

environment is carried out through a spherical robot which is

controlled and manipulated by the patient while performing

the rehabilitation tasks determined by the virtual work

environment. The development of the virtual environment will

allow the spherical robot to emit an input signal to the virtual

environment that is analyzed to indicate whether the patient

successfully fulfilled the defined task by increasing the

complexity of the treatment, otherwise the instructions of the

rehabilitation process are repeated. In Fig. 2, the block

diagram proposed for the development of the virtual

environment is shown, which is divided into five parts.

System inputs, the input devices of the carpal tunnel

rehabilitation treatment system allow the capture of signals to

be interpreted and perform a predetermined action. The

devices used as inputs are: i) GearVR, this virtual device

allows the immersion of the patient in the virtual environment,

stimulating him to perform the rehabilitation treatment

proposed by the specialist; ii) Robot Sphero, this electronic

device allows bilateral interaction between the patient and the

virtual interface. Through the manipulation of the robot the

information is sent to fulfill the proposed rehabilitation task

while the virtual environment closes the control loop feeds the

patient through the robot Sphero the movement that must be

executed to perform the proposed task.

Figure 2. Block diagram of the virtual environment

Outputs: he system consists of electronic devices that emulate

movements, environments, sounds, among others; these output

devices are: virtual reality helmet, audio speakers and the

spherical robot that executes the movements according to the

fulfillment of the patient's rehabilitation treatment.

Virtual environment: the virtual reality environment is

developed in order to motivate the patient to carry out the

rehabilitation treatment proposed by the specialist, according

to the evolution of the patient, the complexity of the treatment

57

is increased allowing to record a record of compliance and

advances of the patient; the virtual environment was

developed on the Unity 3D platform, where it has the

respective programming of scripts that allow interacting with

the inputs and outputs of the system.

Control stage: the proposed control for the rehabilitation

treatment provides the patient's interaction in the virtual

environment through the feedback of position and speed by

means of the robot Sphero. The Sphero robot is capable of

sending and receiving signals with respect to the reference

system ( ),R X Y Fig. 3; As the patient manipulates the robot in

a coordinated and cooperative way, he will receive the

positions directly XP , YP and orientation 𝜓 allow for

monitoring in the execution of the treatment in order to

improve the rehabilitation process.

Figure 3. Reference system of Sphero Robot

Virtualization, the virtual rehabilitation environment provides

the patient with the necessary information, so that the

fulfillment of the tasks is understandable and friendly, i.e., the

environments created have a high level of immersion and

interaction with the patient. Immersion considers visual,

auditory and correction signals XF , YF , these are the ones in

charge of motivating and helping the patient in fulfilling the

tasks; while the interaction is effected through the Sphero

robot that sends the position XP , and orientation 𝜓 to the

virtual environment.

For the rehabilitation treatment of the carpal tunnel, is work in

two scenarios illustrated in Fig. 4, i) Safe box scenario,

instruction is presented that allows to open the safe for the

purpose that the patient moves from right to left the wrist; ii)

Labyrinth scenario. the exercises performed allow to stretch

the release of the pressure exerted by the median nerve.

(a) Safe box scenario

(b) Labyrinth scenario

Figure 4. Rehabilitation Scenarios

IV. METHODOLOGIC AND ANALYSIS

This section presents the methodology for the application of

interactive games using simulated instructions and actions,

using virtual reality and the Sphero robot, which are oriented

towards patients with STS depending on the intensity level of

the syndrome. The games present a series of exercises where it

is possible to control hand movement and record patient

information such as: i) intensity of movement ii) direction of

movement iii) duration of the exercise. Thus, is possible to

analyze the progress of rehabilitation, as well as the patient's

acceptability to the use of virtual environments as an

alternative treatment for STS. Depending on the specialist's

recommendations, two types of games have been proposed:

A. Game of Safe box

The game shows a safe that must be opened, entering the

correct combination, for this purpose the instructions to be

followed by the patient are indicated, i.e. position and

orientation. Each time a task is completed, the results are

displayed to record the progress of therapy. The game

interface is shown in the Fig4.

(a) Instructions

58

((b) Turn 30o to the left

(b) Turm 60o to the rigth

(c) Turm 55o to the left

(d) Error in instructions

Figure 5. Environment Game of Safe box

In this game, the patient must hold the Sphero simulating the

wheel to make movements from left to right, with many

repetitions given randomly, thus is possible to improve the

mobility of tissues that are being rehabilitated.

B. Game of Labyrinth

Applying an interactive virtual environment, it is proposed to

use the Sphero to mobilize within a labyrinth, in this game

obstacles and rewards are presented, so that in the course the

patient can be gaining points each time he catches a group of

coins, while if he collides with an obstacle will be penalized

returning to the initial location (see Fig.5).

Figure 6. Environment Game Labyrinth

While the game is running, the patient makes slight

movements from left to right and back and forth, if the patient

deviates from the predetermined path or collides with an

obstacle, the Sphero robot will send a correction signal that is

generated by means of force feedback.

Finally, to establish the interest in these games, a usability test

was carried out with two groups of people: i) patients (Qp)

who have undergone CTS treatment, and ii) physiotherapists.

For the first group, 4 CTS patients were considered who

59

combined traditional rehabilitation with two rehabilitation

sessions using the virtual tool. The second group included 3

physiotherapists, who interacted with the games so that they

could evaluate the experience in relation to the environment

and familiarization with the application. Fig. 6 shows the

results obtained for the questions posed with ten being the

highest weighting and zero the lowest weighting.

Table 1: Questions to evaluate the usability of the virtual

environment

Questions

Qp1. How familiar are you with handling devices that allow

immersion in virtual environments?

Qp2. Is the management of virtual environments easy?

Qp3. Is the execution of the games simple and intuitive?

Qp4. Are the limitations given by external noise (light, depth)

imperceptible?

Qp5. Does the equipment used cause no discomfort?

Qd1. Are patients motivated with this type of tool to perform

rehabilitation therapies?

Qd2. Does the system facilitate obtaining information about

the progress of rehabilitation?

Qd3. Does the incorporation of new games facilitate the

development of exercise routines?

Qd4 Does the system facilitate the detection of errors in

rehabilitation?

Qd5. Can the system be implemented for rehabilitation due to

similar traumas?

Figure 7. Questions results

In Fig. 6, it can be observed that both patients and

physiotherapists have acceptance for the use of this type of

exercise games to perform CTS therapies, also show the

possibility that they can be applied for the recovery of other

types of trauma.

V. CONCLUSION

In this work, a virtual system has been developed to

quantify the value of the CTS rehabilitation treatment variable

through a Sphero robot. The Sphero robot accepts linear and

angular displacements as inputs, while as outputs it provides

force and torque, which are used for system feedback

according to the type of rehabilitation movement the patient

performs.

The results obtained in the virtual environment implemented

for people suffering from STS show the efficiency of the

proposed system; the system developed was tested with

patients of different gender and age, under the supervision of a

physiotherapist who verified the validity of the movement, and

the results obtained were counteracted with traditional

therapies.

The system presents two series of virtual exercises, one in

which repetitive movements are performed to strengthen the

tissues and measure the patient's hand's ability to move; and

the other game presents a playful environment, giving the

patient greater security since it participates in the therapy as a

game and not as a therapeutic procedure, this method aims to

change the usual position of the hand or generate shocks that

help reduce pain or discomfort produced as a symptom.

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Randmized Controlled Trials, Archives of Physical Medicine and

Rehabilitation, 2017 [4] Stocker, R. L., Macheiner, A.: Capitate Non-Union: One of the Causes

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Chirurgie: Organ der Deutschsprachigen Arbeitsgemeinschaft fur Handchirurgie, vol. 48, no 3, p. 171-174, 2016.

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syndrome. BMC musculoskeletal disorders, vol. 17, pp.115-125, 2016. [6] Fernández-de-las-Peñas, C., Fernández-Muñoz, J. J., Palacios-Ceña, M.,

Navarro-Pardo, E., Ambite-Quesada, S., & Salom-Moreno, J.: Direct

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D., and Andaluz, V.H.: Assistance System for Rehabilitation and

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60

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61

Virtual Assistant of

Training Routines Physical Movements

Fernando A. Chicaiza, Christian P. Carvajal, Luis Lema-Cerda, Washington X. Quevedo, Marcelo Álvarez,

Jessica S. Ortiz, Jorge S. Sánchez and Víctor H. Andaluz Universidad de las Fuerzas Armadas ESPE, Sangolquí-Ecuador

fachicaiza@ingenius-scitech.com; chriss2592@hotmail.com

lalema, wxquevedo, rmalvarez, jsortiz4, jssanchez, vhandaluz1@espe.edu.ec

Abstract— This article proposes a virtual system to stimulate

the executing of physical movements routines for both, the upper

and lower limbs. The system contemplates some virtual

environments for human-computer interaction, depending on the

type of routines of exercises that the user wishes to perform, i.e.,

workout routines to lose weight, define and mark muscles, and so

on. For any selected workout routine, the interface allows

visualizing both the routine of movements that must be made by

the user, as well as the real movement executed by them. This

information is relevant for the purpose of i) stimulating the user

during the execution of movement routines, and ii) evaluating the

movements made so that the virtual personal trainer can

diagnose the evolution of the user. The visual environment

developed is based on a systematic application which the user

first analyzes and generates the necessary movements in order to

complete the defined task. The results show the efficiency of the

system generated by the human-computer interaction oriented to

the physical movement of motor skills.

Index Terms— Virtual Assistant, Virtual Reality, Training

Routines, Physical Movements.

I. INTRODUCTION

In recent years, human beings have turned to extreme

monotony in their daily activities, due to excessive comfort

provided by technology, static transportation within vehicles,

and so on, which has repercussions in extreme situations of

sedentary life [1], [2]. The World Health Organization [3]

states that one of the main causes of mortality worldwide is

the lack of physical activity, through the adoption of

cardiovascular disease, cancer and diabetes; it specifically

denotes that [4] is alleged to account for 6% of deaths

worldwide, 21% of breast cancer, 27% of colon cancer and

27% of cases of diabetes approximately. Similarly, a study

developed by the same organization [5] identifies that more

than 81% of adolescents and 23% of adults do not have a

sufficient level of physical activity and whose

recommendation stipulates at least 60 minutes a day of

different types of physical activity.

Starting from this precept, part of the population has

evolved positively towards outdoor sports in controlled

spaces, whose evolution is determined at different levels,

considering the need for mobility [6], the benefits of

cardiovascular characteristics and even the degrees of

association in search of a greater benefit that lead to an

increase in physical activity [7]-[9]. However, the lack of

time, the economic factor, the search for immediate results,

the absence of a personal trainer, eating disorders related to

balanced diets, number of meals per day and even meal times,

influence evidence towards a better physical condition.

Within the contributions of science there are several

applications, tutorial videos which can help people to develop

physical activities with better techniques[11], even within the

social communities are promoted certain miraculous

sequences that will allow the individual to identify results in

an almost immediate manner[12]. The practice of physical

activities in controlled environments, such as the home, gym

or parks, allow people to develop previously programmed

sequences of physical exercises. It is important to consider

that without the presence of a personal trainer, the risks of

injury are high; therefore, the analysis of these behaviors has

been investigated by many fields of science where studies of

systems based on fixed and mobile sensors focused on the

prognosis of human health, the impulse of VR exergames,

which allow to take advantage of virtual reality games to

create customized applications through different work

environments [13]-[20].

As described in previous paragraphs, this work proposes the

implementation of a bilateral virtual system between user-

computer applied to physical movement training routines of

upper and lower extremities. The application is developed in a

3D graphic engine which allows interaction and immersion of

the operator in friendly environments that stimulates the

execution of different training routines aimed at weight loss

and definition of muscles. The developed system allows the

user to assess the routine of exercises performed based on the

exercises proposed by the virtual personal trainer.

This article is split into 7 Sections, including Introduction

and References. Section 2 presents the structure of the

proposed virtual system; while the valuation of movements

performed by the user and the virtual training interface are

presented in Section 3 and Section 4, respectively. The

experimental results that validate the proposal are shown in

Section 5; and finally, the conclusions are detailed in Section

6.

62

II. VIRTUAL STRUCTURE SYSTEM

This paper presents the development of an application in a

3D virtual environment that offers users an alternative to

perform some assisted physical activities routines for upper

and lower extremities. In addition, the proposed application

allows routines to have a pre-evaluation of the execution of

movements during a pre-established routine; this information

will allow the personal trainer to carry out detailed studies and

analyzes of the progress of each user, and thus determine the

evolution of the user before the different physical routines of

exercises developed by the user.

The virtual personal trainer, developed in this work, allows

to have a feedback of movements through points that

represent the exoskeleton of the user, see Figure 1.

Figure 1: Skeleton tracking

This virtual system is safe and also entertains the user while

he/she is working out. Figure 2 describes the interaction of the

user with the proposed system, establishing as the main

element of the communication the visual feedback that

encompasses the two main actions within a virtual

environment, observe and act.

The interaction between the patient and the system is

established through bilateral communication, i.e., first a

graphical interface shows the movement of the exoskeleton

that the user must execute; second the user generates the

movement trying to complete the preset routine. In real time

the Kinect 2 device tracks the user's skeleton in order to

determine if the movements performed resemble those pre-

defined by the virtual personal trainer. In addition, in the

virtual environment where the user executes his physical

activities routine, the mirror effect was implemented which

through visual feedback will allow the user to correct the

movements he is executing in order to successfully perform

the defined session, i.e., the user's neuronal system becomes

in the controller of a closed-loop control system. The visual

environment developed for this type of virtual personal trainer

provides a systematic application which the user first analyzes

and generates the necessary movements in order to complete

the defined task.

NEURAL

SYSTEMVISION

MOTOR

SKILLS

UNITY 3D

(COMPUTER)

VISION

SENSOR

GRAPHICS

PATIENT MACHINE

VISUAL FEEDBACK

Figure 2: Training System block diagram

The virtual system developed is implemented on Unity 3D

graphics engine; environments in which several scenarios are

considered in order to stimulate the user's neuronal system

when executing the physical movements routines. It proposes

the valorization of the movements made by users with the

purpose of validating and diagnosing the progress the

evolution of the user before the different routines

implemented.

The programming for the operation of the scene in virtual

reality and in augmented reality graphically shown in Figure

3, which links the components with the mechanics of

movements performed by a person in front of a body tracking

device.

Figure 3: Training System Scheme

In section i) the scenes in Virtual and Augmented Reality

are developed which are chosen in the user interface at the

moment of starting the application. There are also objects that

show the data captured by the Kinect device, as well as

cameras and auxiliary objects.

63

Section ii) corresponds to SCRIPTS, where you have the

main application controller which operate all interactions and

displays information in virtual reality and augmented reality

environments by management the inputs: Kinect, Oculus

SDK, and Input / Output plugin. It uses an algorithm that

reads the positions of joints in space and overlays them to the

color image that the Kinect device captures. By means of

position comparators it is determined if the user's movements

are correct. It also has a controller to export the data acquired

from the user to databases so that external analysis can

perform analyzes that require dedicated calculation potential.

In section iii) of Outputs, the resulting responses of inputs

and interaction with the user interface are received in audio,

video and tracking outputs.

III. TASK EVALUATION

The development of the application is based on the

technology Kinect v2 that allows to measure objectively and

accurately the positions of the main joints of a human body.

The Figure 4 shows the skeleton of the user represented by 24

points, the position x - y - z of the reference points is

obtained through the function Skeleton Frame Ready with

respect to a global reference 3R< > frame located on the

Kinect device.

For the evaluation of the movements during the execution

of the test, the final positions of the reference points in the

extremities, the vectors used are; pqa for the arm ,where

:p represents the exact point of reference of s =shoulder,

e =elbow, w =wrist, h =hand, t = thumb y ht = tip of the

hand; and the position of the arm r = right or l = left, that is

the vector ( ), ,sr sr sr srx y za = would represent the position of

the right shoulder; of similar shape for the leg pql , where

:p represents the exact point of reference of h =hip,

k =knee, a =ankle, and f =foot ; and :q r = right or l =

left; for the central part of the body the references are

considered: ht for the head, sht for the central part of the

shoulders, st for the central part of the spine y ht for the

central part of the hip.

Figure 4: Representation of the assessment of the test and Tracking points

through Kinect v2

The application used is executed within the vector space of 3R< > . To measure the angles of the limbs in different

positions we use metrics defined in an Euclidean Space, for

the angle measurement the expression is used

cosi j

i j

v v

v v = , where

iv and

jv are obtained from the

difference between the coordinates of the reference points,

e.g., i sl el

v a a= − and j el wl

v a a= − , to obtain the modulus of

the vectors representing the limbs we use the definition of

norm i i i

v v v= , with these data you can evaluate each

of the tests that are required, Fig 4.

IV. VIRTUAL TRAINING INTERFACE

The application developed in Unity presents a user interface

with two profiles: i) The Trainer Gym; and ii) User, in which

the workout is tracked.

The gym trainer profile requests user input and password,

in order to contrast with the credentials stored in the database,

once access is authorized, forms are displayed that allow the

administration of information and user therapies, in which

CRUD operations (Create, Read, Update, Delete) are applied

with the corresponding records. In this profile you can find the

search option to find registered users and continue with the

appropriate physical training, the system allows you to select

from among several training levels to be applied in a virtual

way and finally present a report in which the Advances of the

person who meets the exercise routine.

2: [compare:true]

login and

password

3:

[con

ectio

n:tru

e]

Use

r inf

orm

atio

n

4:

[conectio

n:tru

e]

User

info

rmatio

n

4: [Training

given:]

Charged TrainingVirtual

System

1: [conection:true]

get login and

password

5:

[con

ectio

n:tru

e]

traki

ng

info

rmat

ion

Figure 5: Diagram of the user interface

The profile of the user asks for entering the username and

password and start the training routine, Figure 5. The

exercises can be done in an environment outside the office

and even at home if you have the necessary equipment, for

which they have defined two environments: Virtual reality

focused on people who want greater immersion in the virtual

environment by incorporating images and sounds that provide

a greater stimulus when performing the exercises, in this

64

environment you have the possibility to observe the

movements and ensure the correct realization of them; The

Augmented Reality is aimed at people who do not accept

invasive devices, in this environment the data obtained from

the Kinect is shown, which form a vectorized skeleton that

indicates the user's current position, in parallel, the user's

image it is shown in real time and the graphic of a reference

profile is superimposed with the image of the person who

performs the exercise, which allows to know the anatomical

position of each part of the body, as shown in Figure 6; the

information generated is stored in a database for further

analysis.

2: [compare:true]

login and

password

3: [T

rack

ing]

data

1:

[conection:true]

get login and

password

Figure 6: System Virtual functional diagram

The information stored in the database is processed using a

computational tool for statistical analysis, the evaluation of

the results can be shown graphically and numerically, in this

way the gym trainer can apply this information at the next

level of training.

V. RESULTS

The application results are split into two parts: a sequential

set of windows which allow the choice of various parameters

prior to the execution of an exercise and experimental tests,

both of them presented in this Section.

Interface panels: The set of sub windows are divided into

home panel, personal trainer, scenarios, and exercises, which

provide the configuration of the work environment.

Home panel: It is the main window that stores user

information (Figure 7) in order to generate historical data of

avatar type, scenario, and exercises that are frequently

selected. Otherwise, it is allowed to add information about

new users.

Figure 7: Home panel

Avatar panel: The objective of the avatar is to guide the

exercise to avoid wrong executions that may cause damage to

the performer's joints, as well as show the speed of execution

to properly develop the task. Figure 8 shows the kind of avatar

that can be selected, from which action figures and

professional trainers are presented.

Figure 8: Selectable avatar types

Scenarios: The main purpose of this selection is to

familiarize the user with the place where the exercises are

performed. The scenarios (Figure 9) are completely

virtualized so the user can have a high degree of immersion,

where they can visualize the avatar executing the exercises in

the entire virtual space. The options show a gym, a park and a

castle, the first two with people and the third option without

people.

Exercises: The exercise panel (Figure 10) is completely

varied. Tasks to exercise muscles of the upper extremities

(biceps brachial, triceps brachial, deltoids) and lower

(quadriceps, biceps fémoral, calf muscles), abdominals, grand

pectorals, back and gluteal muscles are shown by the chosen

avatar, so the user has a clear perspective on the exercise

which is going to select.

Figure 9: Selectable scenarios types

65

Figure 10: Selection of exercises

Work environment: Once the parameters for the execution

of exercises have been selected, the work environment

includes the avatar, the scenario, and the type of exercise. In

addition to this, the environment shows a screen where the

user can visualize their execution, with the aim of giving

feedback to the visual information which is lost due to the

inclusion of virtual reality glasses.

The work environment additionally displays a panel for

modifying the characteristics of the current music track, as

well as changing either the next or previous track or album

stored in an internal database of the program. The

modification for the change in the music tracks is carried out

with a set of corporal movements that the algorithm

recognizes.

Experimental tests: The results of the interface created in

virtual reality are validated with real tests developed by a

group of people. To detail the designed environment, this

section presents a group of captures of the execution of two

exercises: the first one for arms and another one for legs.

The first task (Figure 11) requires the user to exercise the

biceps muscle, a routine that is constantly being evaluated by

the Kinect sensor. The correct execution requires the user to

keep his back in a safe position while descending and

ascending a dumbbell. For the exercise to be successfully

developed, the number of repetitions and the speed of

execution must be as close as possible to the guiding avatar.

The coincidence in the execution of the exercise is evaluated

online by an internal comparison algorithm, which

accumulates the amount of time the user stays in the desired

positions. When the threshold of expected positions exceeds

an acceptable factor, the result of the task is considered

successful, otherwise, the interface shows a message of

erroneous execution.

The second task shown (Figure 12) as an example is called

dumbbell lunges, which consists of working out quadriceps,

glutes, and biceps fémoral. The internal algorithm calculates

the amount of fat burned depending on the exercise and the

user's weight. This information is included in the lower right,

allowing the user to know the evolution of the exercise.

Likewise, the training environment includes options to back

home, which allows the user to select new routines or select

another avatar as a training guide.

Remark: The whole information of the exercise, fat

burned, execution time, heart rate and other configurations are

automatically stored in a database.

a)

b)

c)

Figure 11: Execution of the first experimental test

a)

b)

c)

66

Figure 12: Execution of the second experimental test

VI. CONCLUSION

This work proposes a virtual reality application for routines

of physical movements aimed at losing weight, tone and

define muscles. The implemented system considers a sensor

for the tracking skeleton of the user, sensors for the

acquisition of bioelectric signals and virtual reality immersion

glasses. The virtual environment is configured with the user

personal data, which allows selecting the avatar in order to

stimulate the correct execution of physical movements

proposed by the virtual personal trainer. Additionally, the

system allows immersion and interaction with the virtual

environment, with the purpose of knowing the user's

bioelectric information, e.g., number of fat burned, heart rate

per minute and execution time of the exercise.

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