Voice Controlled Wheelchair

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Voice Controlled Wheelchair

CHAPTER 1

INTRODUCTION

This topic aims at controlling a wheelchair for handicaps by means of human

voice.The speech recognition system is a useful way of implementation and is easy to

use programmable speech recognition circuit. Programmable, in the sense that user can

train the words (or vocal utterances) he needs the circuit to recognize. This board allows

the user to experiment with many facets of speech recognition technology. It has 8-bit

data out, which can be interfaced with any micro controller for further development.

Some of interfacing applications which can be made are controlling home appliances,

wheelchair movements, Speech Assisted technologies, Speech to text translation, and

many more.

The wheelchair is controlled by voice commands. This can be moved in forward

and reverse direction using geared motors of 60RPM. Also this wheelchair is a type of

robot which can take sharp turnings towards left and right directions. It uses PIC16F72

MCU as its controller. It uses 6V battery.

1.1 BASIC IDEA :

In this topic, the controlling of a wheelchair by speech will be studied. Commands

are spoken into a microphone, followed by an action by the wheelchair. Voice Controlled

Wheelchair is a kind of a mobile robot whose motions can be controlled by the user by

giving specific voice commands. The speech recognition software running on a PC is

capable of identifying the 5 voice commands Run, Stop, Left, Right and Back

issued by a particular user. After processing the speech, the necessary motion instructions

are given to the mobile platform via a RF link.

Department of Electronic & Communication Engineering

K.B.N College of Engineering, Gulbarga

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The speech recognition software is speaker dependant. The special feature of the

application is the ability of the software to train itself for the voice commands(Run,

Stop, Left, Right and Back) for a particular user. The graphical user interface

running along with the software provides a very convenient method for the users to train.

It also provides many other facilities in operating the wheelchair.

In this topic we will be using visual basic (VB6.0) as our speech recognition application.

Figure 1.1: Block diagram of Voice Controlled Wheelchair



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CHAPTER 2

COMPONENT

2.1 MAIN COMPONENTS:

PIC 16f72 Microcontroller

RF 434MHz Tx-Rx

Electro-magnetic Relays

Mike/ Microphone

Geared motors

Serial port- RS232

2.2 OTHER COMPONENTS:

Diode

Resistors

IC 7805- Voltage regulator

Battery

Crystal oscillator

LED

PCB

IC base



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2.3 POWER SUPPLY:

Power supply is the basic requirement of any electronics device.we have used a

6V battery to run the 60RPM geared motors. 9V batteries are used to run the relay circuit

and RF 434MHz Tx-Rx. 12V power supply will be provided by the PC which would beconverted into 5V by Voltage Regulator (7805).

2.3.1 VOLTAGE REGULATOR:

The Digilab board can use any power supply that creates a DC voltage between 6

and 12 volts. A 5V voltage regulator (7805) is used to ensure that no more than 5V is

delivered to the Digilab board regardless of the voltage present at the J12 connector

(provided that voltage is less than 12VDC). The regulator functions by using a diode to

clamp the output voltage at 5VDC regardless of the input voltage - excess voltage is

converted to heat and dissipated through the body of the regulator. If a DC supply of

greater than 12V is used, excessive heat will be generated, and the board may be

damaged. If a DC supply of less than 5V is used, insufficient voltage will be present at

the regulators output.

Figure 2.3.1: Voltage Regulator



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If a power supply provides a voltage higher than 7 or 8 volts, the regulator must

dissipate significant heat. The "fin" on the regulator body (the side that protrudes upward

beyond the main body of the part) helps to dissipate excess heat more efficiently. If the

board requires higher currents (due to the use of peripheral devices or larger breadboard

circuits), then the regulator may need to dissipate more heat. In this case, the regulator

can be secured to the circuit board by fastening it with a screw and nut (see below). By

securing the regulator tightly to the circuit board, excess heat can be passed to the board

and then radiated away

Figure 2.3.2: Regulator Implemented on a PCB

We have used a L.E.D as an indicator that indicates the conversion of ac voltage

into dc. When the transformation is done the L.E.D glows and it continues to do so till

there is supply available for the circuit to work.

Figure 2.3.3.: Power Supply Circuit



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2.4 PIC 16F72 MICROCONTROLLER:

We use microcontroller PIC 16f72, which is at the upper end of the mid-range

series of the microcontrollers developed by Microchip Inc. It is characterized by RISCarchitecture instead of the CISC architecture used, for example, by the Motorola 6809.

The PIC series of microcontrollers are RISC-based processors with an

accumulator (also called the working register, W), which use the Harvard3 architecture;

therefore the microcontroller has a program memory data bus and a data memory data

bus. Separate buses mean that simultaneous access of program and data can be done,

which gives a greater bandwidth over the traditional won Neumann architecture.

Separating the program and data memory, allows instructions to be sized differently than

the 8-bit wide data word. This separation means that the instruction words can be ideally

sized for the specific CPU/application. This is necessary since RISC architectures require

that instructions have the source and destination operands be encoded within the

instruction.

High Performance RISC CPU:

Only 35 single word instructions to learn

All single cycle instructions except for program branches, which are two-cycle

Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle

2K x 14 words of Program Memory, 128 x 8 bytes of Data Memory (RAM)

Pinout compatible to PIC16C72/72A and PIC16F872

Interrupt capability

Eight-level deep hardware stack

Direct, Indirect and Relative Addressing modes



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Special Micro controller Features: 1,000 erase/write cycle FLASH program memory typical

Power-on Reset (POR), Power-up Timer (PWRT) and Oscillator Start-up Timer

(OST)

Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation

Programmable code protection

Power saving SLEEP mode

Selectable oscillator options

In-Circuit Serial Programming (ICSP) via 2 pins

Processor read access to program memory



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Figure 2.4.1 : Pin diagram


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2.4.1 DESCRIPTION OF 16f72:

The PIC16F72 belongs to the Mid-Range family of the PIC micro devices.

The program memory contains 2K words, which translate to 2048 instructions, since each14-bit program memory word is the same width as each device instruction. The data

memory (RAM) contains 128 bytes.

There are 22 I/O pins that are user configurable on a pin-to-pin basis. Some pins

are multiplexed with other device functions. These functions include:

External interrupt

Change on PORTB interrupts

Timer0 clock input

Timer1 clock/oscillator

Capture/Compare/PWM

A/D converter

SPI/I2C



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2.4.2 BLOCK DIAGRAM OF PIC 16f72:

Figure 2.4.2 : Block diagram of 16f72



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2.4.3 MEMORY ORGANIZATION:

There are two memory blocks in the PIC16F72 device. These are the program

memory and the data memory. Each block has separate buses so that concurrent access

can occur. Program memory and data memory are explained in this section. Program

memory can be read internally by the user code. The data memory can further be broken

down into the general purpose RAM and the Special Function Registers (SFRs). The

operations of the SFRs that control the core are described below. The SFRs used to

control the peripheral modules are described in the section discussing each individual

peripheral module.

2.4.3.1 DATA MEMORY ORGANIZATION:

The Data Memory is partitioned into multiple banks that contain the General

Purpose Registers and the Special Function Registers. Bits RP1 (STATUS) and RP0

(STATUS) are the bank select bits.

Each bank extends up to 7Fh (128 bytes). The lower locations of each bank are

reserved for the Special Function Registers. Above the Special Function Registers are

General Purpose Registers, implemented as static RAM. All implemented banks contain

SFRs. Some high use SFRs from one bank may be mirrored in another bank, for code

reduction and quicker access (e.g., the STATUS register is in Banks 0 - 3).



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2.4.3.2 GENERAL PURPOSE REGISTER:

The register file can be accessed either directly, or indirectly, through the File

Select Register FSR.

2.4.3.3 SPECIAL FUNCTION REGISTERS:

The Special Function Registers are registers used by the CPU and peripheral

modules for controlling the desired operation of the device. These registers are

implemented as static RAM. The Special Function Registers can be classified into two

sets: core (CPU) and peripheral.

2.4.3.4 STATUS REGISTER:

The STATUS register contains the arithmetic status of the ALU, the RESET

status and the bank select bits for data memory. The STATUS register can be the

destination for any instruction, as with any other register. If the STATUS register is the

destination for an instruction that affects the Z, DC or C bits, then the write to these three

bits is disabled. These bits are set or cleared according to the device logic. Furthermore,

the TO and PD bits are not writable. Therefore, the result of an instruction with the

STATUS register as destination may be different than intended.

STATUS REGISTER (ADDRESS 03h, 83h, 103h, 183h)



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2.5 RF 434MHz Tx-Rx:

Figure 2.5.1 : RF 434MHz Tx-Rx Figure 2.5.2 : RF 434MHz Tx-Rx

2.6 RELAY DRIVER CIRCUIT ULN 2003

The ULN2003 is a monolithic high voltage and high current Darlington transistor

arrays. It consists of seven NPN darlington pairs that features high-voltage outputs with

common-cathode clamp diode for switching inductive loads. The collector-current rating

of a single darlington pair is 500mA. The darlington pairs may be parrlleled for higher

current capability. Applications include relay drivers, hammer drivers, lampdrivers,

display drivers (LED gas discharge), line drivers, and logic buffers. The ULN2003 has a

2.7k series base resistor for each darlington pair for operation directly with TTL or 5V

CMOS devices.

Figure 2.6.1 : Schematic of ULN 2



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2.6.1 RELAY:

Relays are remote control electrical switches that are controlled by another switch,

such as a horn switch or a computer as in a power train control module. Relays allow a

small current flow circuit to control a higher current circuit. Several designs of relays are

in use today, 3- pin, 4-pin, 5-pin, and 6-pin, single switch or dual switches.

2.7 MOTORS:

An electric motor converts electrical energy into mechanical motion. DC motors

drives the wheels of wheel chair.

Figure 2.7 : Working of DC motors

The DC motor has a rotating ligature in the form of an electromagnet. A rotary

switch called a commutator reverses the direction of the electric current twice every

cycle, to flow through the armature so that the poles of the electromagnet push and pull

against the permanent magnets on the outside of the motor. As the poles of the armature

electromagnet pass the poles of the permanent magnets, the commutator reverses the

polarity of the armature electromagnet. During that instant of switching polarity, inertia

keeps the classical motor going in the proper direction.



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The different direction of motions possible is:

Forward: Both the motors in forward direction

Reverse: Both the motors in the reverse direction

Left: Left motor stopped/Right motor in the forward direction

Right: Right motor stopped/Left motor in the forward direction

In turn: The motors are in the opposite direction

Figure 2.7.1 : torque in dc motor



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2.8 MICROPHONE:

The speech of the user is received by a microphone.This is not a high quality

microphone, and in general, the microphone should be a high quality device with noise

filters built in. The speech recognition rate is directly related to the quality of the input.

The recognition rate will be significantly lower or perhaps even unacceptable with a poor

microphone. Therefore it is reason to believe that the performance of this system will

increase with a microphone with higher quality.

2.9 CRYSTAL OSCILLATOR:

Crystal oscillators are oscillators where the primary frequency determining

element is a quartz crystal. Because of the inherent characteristics of the quartz crystal the

crystal oscillator may be held to extreme accuracy of frequency stability. Temperature

compensation may be applied to crystal oscillator to improve thermal stability of crystal

oscillator.

Figure 2.13: Crystal oscillator

Crystal oscillators are usually fixed frequency oscillators where stability and accuracy are

the primary considerations. For example it is almost impossible to design a stable and

accurate LC oscillator for the upper HF and higher frequencies without resorting to some

sort of crystal oscillator.



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2.10. FEATURES:

Glass passivity

High maximum operating temperature

Low leakage current

Excellent stability

Available in ammo-pack.

2.10.1 DESCRIPTION:

A two-terminal semiconductor (rectifying) device that exhibits a nonlinear

current-voltage characteristic. The function of a diode is to allow current in one direction

and to block current in the opposite direction. The terminals of a diode are called the

anode and cathode. Rugged glass package, using a high temperature alloyed construction.

This package is hermetically sealed and fatigues free as coefficients of expansion of all

used parts are matched.



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CHAPTER 3

WORKING

3.1 WORKING:

The speech recognition system is a useful and easy to use programmable speech

recognition circuit. Programmable, in the sense that user can train the words (or vocal

utterances) he needs the circuit to recognize. This board allows the user to experiment

with many facets of speech recognition technology. It has 8 bit data out which can be

interfaced with any microcontroller for further development. Some of interfacing

applications which can be made are controlling home appliances, robotics movements,

Speech Assisted technologies, Speech to text translation, and many more.

Robotics has been of interest to mankind for over hundred years. However our

perception of robots has been influenced by the media and Hollywood. The vast majority

of robots do have several qualities in common. First of all, almost all robots have a

movable body. Some only have motorized wheels, and others have dozens of movable

segments, typically made of metal or plastic. Like the bones in your body, the individual

segments are connected together with joints.

This robot is controlled by voice commands. This can be moved forward and

reverse direction using geared motors of 60RPM. Also this robot can take sharp turnings

towards left and right directions. It uses PIC16F72 MCU as its controller. It uses 12V

battery., mainly useful for industrial applications, surveillance applications. This topic

gives exact concept of controlling a robot by a voice instruction.

The speech recognition system is easy to use programmable speech recognition

circuit. Programmable, in the sense that the system to be trained the words (or vocal

utterances) user wants the circuit to recognize. This board allows us to experiment with

many facets of speech recognition technology. It has 8 bit data out which can be

interfaced with any microcontroller. Some of interfacing applications which can be made



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are controlling home appliances, robotics movements, Speech Assisted technologies,

Speech to text translation, and many more.

Hence this topic uses a speech recognition application installed in a PC. This

application is used through a RS232 port which gives access to the micro controller and

the other hardware circuit. A mike is connected to the PC, when we speak a specific

command whose respective program is stored in the PC through the mike then our

hardware (wheelchair) will move according to the given command. The entire working is

further explained with the help of circuit diagram.

To reduce complexity we have divided the circuit in following parts

1. Power supply

2. PC ( speech recognition application )

3. Motor driving circuit

4. RF transmitter and receiver

5. Microcontroller

3.1.1 POWER SUPPLY:

A battery of 9V is used as the power supply. We are using LM 7805 (IC) for 5V dc. This

is voltage regulator IC. It has 3 pins. One is called input, second pin is common pin &

third pin is output. We can feed 8.5V to 35V unregulated dc at input pin. Input should be

greater than 8V for correct regulation. Second pin is common & generally connected with

ground (- supply). Third pin is output pin & it gives us 5V regulated dc until input pin is

greater than 8V dc.

We are using LM7805 voltage regulator IC because we have one micro-controller in our

circuit. Its voltage range is 2V dc to 6V dc. So we are using 5V dc as international

standard because all digital circuits run on 5V DC.



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Figure 4.1 Circuit diagram of power supply using LM7805

3.1.2 PC (Speech recognition application in VB):

Voice controlled wheelchair requires a speech recognition IC known as HM2007, but this

IC was not available to us. Hence we are using a speech recognition application which isused through VB for recognizing a voice command and performing the required

operation.

Visual Basic (VB) is a third-generation event driven programming language and

associated development environment from Microsoft for its COM programming model.

Visual Basic was derived from BASIC and enables the rapid application development

(RAD) of graphical user interface (GUI) applications, access to databases using DAO,

RDO or ADO and creation of Active X controls and objects. A programmer can put

together an application using the components provided with Visual Basic itself. Programs

written in Visual Basic can also use the Windows API, but doing so requires external

function declarations the language not only allows programmers to create simple GUI

applications, but can also develop complex applications as well. Programming in VB is a

combination of visually arranging components or controls on a form, specifying attributes

and actions of those components, and writing additional lines of code for more

functionality. Since default attributes and actions are defined for the components, a

simple program can be created without the programmer having to write many lines of

code.

For using speech recognition application we have used visual basic which

provides an important Microsoft speech to text converting tool. This tool plays the most

important role in converting a users speech command into text and send respective signal

to the microcontroller to perform the required operation. Fig. 3.9 shows the window of

VB using Microsoft Speech Recognition tool.



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3.1.3 MOTOR DRIVING CIRCUIT:

A motor driver is a device or group of devices that serves to govern in some

predetermined manner the performance of an electric motor.

A motor controller might include a manual or automatic means for starting and

stopping the motor, selecting forward or reverse rotation, selecting and regulating the

speed, regulating or limiting the torque, and protecting against overloads and faults.

All types of engine-driven vehicles from automobiles, airplanes, aircraft carriers

and agricultural equipment to ambones may have electric motors to perform a variety of

functions. In electric vehicles, diesel-electric vehicles, and hybrid vehicles, electric

motors are used to propel the vehicle. The motor controllers in vehicle applications areintegrated into the vehicle.

An electric motor controller can be classified by the type of motor it is to drive

such as permanent magnet, servo, series, separately excited, and alternating current. A

motor controller is connected to a power source such as a battery pack or power supply,

and control circuitry in the form of analog or digital input signals.

DC motors are typically controlled by using a transistor configuration called an

"H-bridge". This consists of a minimum of four mechanical or solid-state switches, such

as two NPN and two PNP transistors. One NPN and one PNP transistor are activated at a

time. Both NPN and PNP transistors can be activated to cause a short across the motor

terminals, which can be useful for slowing down the motor from the resistance it creates.

There are two motors in our wheelchair which drive the two wheels in forward, reverse,

left and right directions. The motors are controlled through two identical circuits known

as H-bridge. An H-bridge is an electronic circuit which enables DC electric motors to be

run forwards or backwards.

These circuits are often used in robotics. H-bridges are available as integrated

circuits, or can be built from separate components. The term "H-bridge" is derived from

the typical graphical representation of such a circuit. An H-bridge is built with four

switches (solid-state or mechanical). The first switch is connected from the high voltage

bus to the first terminal of the DC motor.



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The second switch connects the second terminal of the DC motor to the low

voltage bus. The third switch is connected between the high voltage bus and the second

terminal of the DC motor. The fourth and final switch links the first terminal of the DC

motor to the low voltage bus.

When the first and second switches are closed (and the third and fourth are open)

a positive voltage will be applied across the motor between the first and second terminals.

By opening the first and second switches and closing the third and fourth switches, this

voltage is reversed, allowing reverse operation of the motor. Figure 3.9 shows the circuit-

diagram of an H-bridge operating a dc motor.

Figure 3.1.3 Circuit diagram of H-bridge

3.1.4 RF TRANSMITTER AND RECEIVER:

A 434 MHz RF transmitter and receiver are used for making the wheelchair

wireless. The transmitter is connected to the computer which transmits the signal

equivalent to the given command by the user. The RF transmitter is set with the software

part using MAX232 while the RF receiver is set on the hardware part of topic. The

function of RF receiver is to receive the signals from transmitter and provide serial data to

microcontroller to perform the required operation.



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3.1.5 MICROCONTROLLER (PIC16F72):

A microcontroller is an important part of any robot, it receives input signal and

performs the desired operation. The microcontroller we are using is PIC16F72 for taking

the serial data from PC and control the movement of the wheelchair.

This microcontroller is based on RISC (Reduced Instruction Set Computing), it

also uses CMOS technology. It has basically 35 instruction sets, also provides direct,

indirect and relative addressing modes. The clock input is of 20 MHz frequency and

instruction cycle time is 200 ns. It has 28 pins and 3 input and output ports namely port A,

port B and port C. The entire working of the circuit is further explained with the help ofcircuit diagram. In our circuit pin number 8 and 19 are grounded, while pin 1 is connected

to a 4.7K resistance and a switch. Pin number 9 and 10 are used to connect the crystal

oscillator of 4MHz to give the clock signals. Pin number 20 is connected to high voltage

supply Vdc (5V). The pins of port C are used to receive i/p and provide o/p to the H-

bridge. Pin number 15 is connected to RF receiver to receive i/p data from the transmitter,

while pin number 11 and 12 are connected to first H-bridge and so do pin number 13 and

14 to second H-bridge.



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3.1.6 CIRCUIT DIAGRAM:

U 1

1

9

1 0

2 0

2

3

4

5

6

7

2 1

2 2

2 3

2 4

2 5

2 6

2 7

2 8

1 1

1 2

1 3

1 4

1 5

1 6

1 7

1 8

M C L R / V P P

O S C 1 / C L K I N

O S C 2 / C L K O U T

V D D

R A 0 / A N 0

R A 1 / A N 1

R A 2 / A N 2

R A 3 / A N 3 / V R E F

R A 4 / T O C K I

R A 5 / S S / A N 4

R B 0 / I N T

R B 1

R B 2

R B 3

R B 4

R B 5

R B 6

R B 7

R C 0 / T 1 O S O / T 1 C K I

R C 1 / T 1 O S I

R C 2 / C C P 1

R C 3 / S C K / S C L

R C 4 / S D I / S D A

R C 5 / S D O

R C 6

R C 7

C r y s t a l O c s 4 M h z

R F R e c e i v e r

5 V

R 1

4 . 7 K

M o t o r 1

5 V

M o t o r 2

S W 1

5 V

P I C 1 6 F 7 2

5 V

5 V

V C C

Figure 4.4 Circuit diagrams of micro controller and motor driver.

The working of voice-operated wheelchair can be explained in the following steps-

Step 1- The very first step requires installing the software used for voice recognition i.e.

VB 6.0 along with the additional Microsoft direct text-speech tool on a computer.

Step 2- After installing the software we check the working of our software part by

speaking through mike, if the front end of VB recognizes the command then it shows a

message box in which the spoken command is written.

Step 3- Once the speech recognition part is installed and checked then comes the

connecting of RF transmitter to the serial port of PC using MAX232 and a 9V battery is

also connected to the transmitter for running it. The transmitter receives serial data from

the PC and transmits it.

Step 4- Now we connect the 9V batteries to RF receiver, two H-bridge circuits and the

voltage regulator. Now our hardware is ready to receive command and move according to

the user.



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Step 5- Now when the user speaks a command in to mike then a transmitted signal is

received is then it is send to the i/p pin of port C (C4 i.e. 15) and the microcontroller reads

the command and compares the values of port C according to the following table.

Operation C0 C1 C2 C3

Forward High Low High Low

Backward Low High Low High

Right Low High High Low

Left High Low Low High

Table 4-1: Direction of wheelchair

As the above table describes the various movements of wheelchair due to the high

and low values set by the microcontroller to the o/p pins of port C i.e pin number from

11-14 (C0, C1, C2, C3). The pin C0 and C1 of port C are connected to the H-bridge

which operates motor1 while pin C2 and C3 are connected to the other H-bridge which

controls movement of motor2. Thus the two motors move according to the data on o/p

pins of port C and our wheelchair moves in the required direction.



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CHAPTER 4

CONCLUSION

The goal of this topic to develop a speech controlled wheelchair application for

the handicapped and physically paralyzed patients. The goals were fulfilled with quite

good results. In this case Visual Basic was used, a programming language that is easy to

learn and use but yet powerful enough to make wheelchair control systems. With fairly

limited code it is possible to reach high wheelchair control performance. The bottleneck

of the performance lies on the speech recognition part of the system. For users with a

strong accent the performance will not be very high. For people with a good accent, and

even for native speakers, it takes a while to learn how to speak to achieve good results.

When this is learned, the speech recognition performance will be quite high,

although not perfect. The performance can be increased by training the system to a

specific voice and defining a strict grammar were the developer also have in mind what

words can be confused. But the security of the system can be increased, for instance by

implementing a confirm mechanism. Still much of the performance results depend on the

speech recognition programming, which hopefully will improve further.



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REFERENCES

1. Electronic Devices - Robert L. Boylstead and Louis Nashelsky - Pearson

Education Publication - 8th Edition

2. http://www.electronics4u.com/

3. http://www.projectsabtracts.com/

4. http://www.techtriks.wordpress.com/

5. http://www.ideaprojects.com/

6. http://www.datasheetcatalogue.com

7. http://www.alldatasheets.com

Department of Electronic & Communication Engineering 27

Voice Controlled Wheelchair

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