Abstract-- This paper presents the control of elevator system

using Siemens LOGO PLC. The system is programmed to drive a dc motor for forward and backward motoring mode with sensors at each floor, emergency STOP switch for maintenance purpose or to prevent any accident inside the lift & door switch for safety purpose. The system is also programmed to conserve energy by automatically switch off lights and fans of cabin when motor is in rest state for a specified duration of time. The software used in this elevator system is LOGO! Soft Comfort V7.0. This system can be used for learning the control strategies involved in elevator systems for educational purpose.

Index Terms — Automation, Energy saving, Elevator, Ladder

logic and Programmable Logic Controller (PLC).

I. INTRODUCTION N modern time due to rapid population growth in the urban areas, in multi-stored buildings need for elevators is being increased. With rising life standards and attention towards

safety measures and with the development in modern technologic, elevator systems are getting better, fast and more reliable. In the past, most of the elevator systems were focused on the mounting of elevators, around 1980s the need for elevator maintenance and fault staff had started to increase [1]. For example, splash doors have been replaced by automatic doors system, cards with relay have been replaced by microprocessor electronic cards, in multi storage building single-speed elevators have been replaced by double-speed or speed-controlled elevators. Such developments improve the quality of elevator systems, therefore increase the reliability of elevator system compared to previous years [2]. Elevator control system [3-4], and its logic analysis [5-6] have been creating interest to engineers and its context scheduling [7] is still in research.

Gurmeet Singh is currently pursuing M.Tech.(Electrical Engineering) NIT Hamirpur, H.P., India. He can be reached at: gsingh.ee@gmail.com

Anshul Agarwal is currently the faculty of Electrical Engineering Department, NIT Hamirpur, H.P., India. He can be reached at: agw.anshul@gmail.com.

R.K. Jarial is currently the faculty of Electrical Engineering Department, NIT Hamirpur, H.P., India. He can be reached at: jarial@nith.ac.in

Vineeta Agarwal is currently the faculty of Electrical Engineering, MNNIT, Allahabad, India. She can be reached at: vineeta_agarwal123@rediffmail.com

Mithun Mondal is currently pursuing M.Tech.(Electrical Engineering) NIT Hamirpur, H.P., India. He can be reached at: mithun1214@gmail.com

978-1-4673-5630-5//13/$31.00 ©2013 IEEE

The objective of this paper is to create the ladder logic programming of a PLC controlled elevator system and control strategies involved in an elevator systems can also be used for educational purpose. The two floor elevator system ladder logic is designed using SIEMENS LOGO! Soft Comfort V7.0 software. SIEMENS LOGO! Soft V7.0 software provide simulation mode for testing of your ladder logic program. PLC can make a conventional elevator system into an automatic, energy saving, safe and reliable elevator system by using various math functions, timers, creating interlocks etc. into its program. The inputs in form of sensors, push buttons etc and output in form of motor, light, fan etc are connected to the PLC input and output terminals.

II. PLC LAYOUT PLC is an electronic device that is used to design the control circuits of industrial automation systems. It controls the system via inputs/outputs and is equipped with communication interfaces. The advantage of using PLC based system is to ensure the high reliability, small space requirements, computing capabilities, reduced costs, ability to withstand harsh environments, expandability, high power handling capacity and reduces the human efforts. The layout of the Siemens LOGO Series PLC is shown in Fig. 1. It has digital / analog input and digital outputs. It has 4 digital and 4 analog inputs and all digital outputs are shown in Table 1. These can be used as per the user’s requirement and also can be extended using extension cards [8].

Fig. 1: Siemens Logo PLC.

PLC Controlled Elevator System Gurmeet Singh, Anshul Agarwal, Member, IEEE, R.K. Jarial, Member, IEEE, Vineeta Agarwal,

Senior Member, IEEE, and Mithun Mondal

I

TABLE I SIEMENS LOGO PLC LABELING

A PLC is divided into parts, as shown in Fig.2 these are the central processing unit (CPU), the input/output (I/O) modules, power supply, and programming device. The CPU is the called as “brain” of PLC, memory is also required for the program (EPROM or EEPROM type plus RAM). The I/O modules form the interface by which field devices are connected to the controller. To enter the desired program into the memory of the processor a programming device is used. The program is done in ladder logic, which is one of the most popular programming languages. Power supply section also supplies DC power to the I/O modules. For large PLC systems, this power supply section does not normally supply power to the field devices. With larger systems, power to field devices is provided by external alternating current (AC) or direct current (DC) sources. For some small micro PLC systems, the power supply may be used to power field devices.

Fig. 2: PLC block diagram.

III. ELEVATOR SYSTEM STRUCTURE The motive of an elevator control system is to control the movement of an elevator according to the user’s requests. It is classified into two parts: A. Electric power driving system

It includes the elevator cabin or car, DC motor and brake mechanism. B. Elevator control system

The elevator’s control system is governed by PLC. The input signals are: car-calls, emergency stop signal, door open/close signal and leveling signal. PLC program contains all logical functions of the elevator system, such as call registration, position judgment of elevator car, choose layer, priority setting.

IV. I/O MODULES AND ELECTRICAL WIRING Elevators were used as vertical traction device, which belong to potential energy load and require frequent start and stop [9]. Elevators are powered by electric motors (DC or AC) that can either drive traction cables or a counter weight systems like a hoist, or pumped hydraulic fluid to raise a cylindrical piston [10-12]. In addition to all these a braking system must also be used [13].The input and output modules of designed elevator system are listed in Table I and Table II. The input devices consists of three floor limit switches, one door limit switch for safety purpose, three floor selector push buttons to select the maximum two floors out of three floors and one emergency stop button to seize the elevator transition instantaneously but PLC will remember its last status and as soon as emergency button is released and the elevator will continue its transition from the moment at which emergency button was pressed. These switches do not consume electricity. These switches are of make break type when it’s open then there resistance in nearly infinite and when they are close then there resistance is around zero. The wiring diagram of PLC is shown in Fig. 3.

TABLE II INPUT LISTING

The output device is a DC motor which can rotate in both direction i.e. clockwise or anticlockwise direction. In ladder logic program interlocks is provided so that elevator moves in one particular direction during transition, otherwise simultaneous operation of motor in both direction can cause wear and tear of motor which can lead to fatal accidents. The other outputs are braking system; fans and lights loads. Fans and lightning loads are connected in parallel to each other i.e. both of them are operate simultaneously. Brakes are applied when motor is switched OFF.

TABLE III

Number Description 1 Rack with 8 inputs (I1 to I8) 4 Digital + 4

Analog 2 Supply rack (L1 – N). 3 Rack with 4 outputs (Q1 to Q4). 4 Multi-character display screen

Input ports Definition Type Location I1 Ground floor call Push button On elevator I2 1st floor call Push button On elevator I3 2nd floor call Push button On elevator I4 Ground floor limit

switch Limit switch Between ground

floor platform I5 1st floor limit

switch Limit switch Between 1st

floor platform I6 2nd floor limit

switch Limit switch Between 2nd

floor platform I7 Door limit switch Limit switch On elevator door I8 Emergency stop Push button On elevator

OUTPUT LISTING

Output port Definition Type Location Q1 Upward

motion DC motor On top of elevator

platform Q2 Downward

motion DC motor On top of elevator

platform Q3 Fan and lights Loads On elevator Q4 Braking system Solenoid On pulley The PLC power supply is 24V DC, all the inputs to the PLC are connected to input ports I1,I2,I3,I4,I5,I6,I7,I8 and all the outputs to the corresponding output ports Q1,Q2,Q3,Q4. The inputs and outputs should be used according to their corresponding addresses while developing ladder logic program.

Fig. 3 Siemens LOGO PLC wiring diagram.

V. OPERATIONAL SEQUENCE The Fig. 4 and Fig. 5 shows the elevator structure developed with I1, I2 and I3 are ground floor, 1st floor and 2nd floor call switches; I8 is an emergency switch; I4, I5 and I6 are limit switches used to detect current lift position. The sequence operation for elevator system is shown in flowchart of Fig.6 and is describe as follow:

• When the person enters in the elevator, light and fan switched ON automatically.

• Desired floors selected by person. • Then the door is closed, motor is switched ON and

brakes released. • The direction of rotation of motor depends upon floor

selected; current elevator position and when the directions are different then the floor selected first will get the higher priority.

• When the selected floor is reached then the limit switch of selected floor gets activated and switch OFF the motor.

• Brakes get activated.

• Selected floor is reached, passenger out of lift and door is closed.

• When none of the floor call switches are pressed up to 40 seconds time duration, then elevator’s cabin fan and light will automatically be switched OFF which will save electricity.

• The whole elevator system is halted by emergency stop button in case of emergency or for maintenance purpose. During this process the elevator’s cabin fan and lights will be ON.

• If there is a power failure during elevator transition, PLC will remember the sequence last status. When power is restored elevator will operate automatically as per there past status.

Fig.4 Floor calls with emergency stop button.

Pulley

Elevator Cabinor Car

CounterWeight

I4

I6

I5

2nd Floor

1st Floor

Ground Floor

Fig.5 Elevator structure

Fig. 6 Flowchart for elevator system

VI. MECHANICAL DESIGN An elevator model is developed which uses a DC motor to pull up the elevator cabin. The dimensions of cabin or car are as follows: Height = 73 mm. Length= 55 mm. Width= 31 mm. Material for cabin construction: Aluminum. Density of Aluminum= 2710 kg/meter3. Weight of cabin= 550 grams (approx.) Weight of counterweight= 500 grams. Radius of pulley = 5 cm Torque required to pull the elevator cabin (Tc) = force × perpendicular distance. = (0.550×9.8) × (0.05) = 0.2695 N-m. Torque provided by counterweight (Tw) = force × perpendicular distance. . = (0.500×9.8) × (0.05) = 0.245 N-m. Net torque required (T) = Tc – Tw = 0.2695-0.245 = 0.0245 N-m. Therefore, the net torque required (T) is supplied by traction motor of specification 0.0300 N-m (0.3 Kg-cm).

VII. IMPLEMENTATION The PLC and motor control panel is shown in Fig.7 and its inner view of the control panel is shown in Fig.8. Ladder logic program is tested for various floor levels, automatic cabin fans and lights are OFF when no one is inside the lift, braking applied when motor is OFF, if there is a power cut when lift is in transition then lift will resume transition when power is restored. Fig. 9 displayed the front view of the lift. When there is a call for 1st and 2nd floor, but the elevator is in ground floor then under this condition the LOGO! Soft comfort view is depicted in Fig. 10. With LOGO! Soft comfort provide online mode in which we can easily get the status of elevator on personnel computer (PC). This system helps us to easily monitor the condition and status of elevator system.

Fig. 7 PLC and Motor control panel

Fig. 8 Inner view of control panel Fig. 9 Lift front view

Fig. 10 Designed view of LOGO! Soft comfort when lift is operated upward.

VIII. CONCLUSION A novel elevator system has been proposed on LOGO! Soft Comfort V7.0 software and implemented on PLC. The PLC controlled elevator system is found to be working effectively and it is the need of modern world, where everything is becoming automatic. The overall system developed can be used in industry, hospital, buildings or can also be used for education purpose. The PLC based elevator system is an efficient tool to conserve electricity when elevator is not in use. The overall system ensures high reliability. Tests have been carried out to show the effectiveness and flexibility of the proposed method.

IX. ACKNOWLEDGEMENT The authors are thankful to the Technology Information Forecasting and Assessment Council and Centres of Relevance and Excellence (TIFAC-CORE) at NIT Hamirpur for providing the necessary facilities to perform the research work.

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