Plc Based Pid Implementation in Process Control of Temperature Flow and Level

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 19-26 © IAEME

19

PLC BASED PID IMPLEMENTATION IN PROCESS

CONTROL OF TEMPERATURE FLOW AND LEVEL

Ramavatar Singh Rathore1, Dr. Anil Kumar Sharma

2, Hirendra Kr. Dubey

3

1M.Tech Scholar, Department of Electronic Instrumentation & Control Engineering

Institute of Engineering & Technology, Alwar-301030 (Raj.), India

2Professor & Principal, Department of Electronics & Communication Engineering


3Alumni, Department of Electronics & Communication Engineering,


ABSTRACT

In the present Industrial scenario the Temperature, Flow, Level, Pressure and density of a

process is controlled using the Proportional-Integral-Derivative (PID) controller which is based on

microcontroller. Out of the above mentioned variables controlling, Temperature control is very

difficult by using ordinary control techniques; hence the motive of our research is to implement

PID controller design along with programmable logic controller (PLC) in order to control the time to

heat up a particular solution to a desired temperature efficiently without sacrificing the stability of

the system. In this work the controlling is based on PLC MISTUBISHI NEXGENIE 1000 NG14RL

along with some Analog cards. In this work the controlling of PID controller is performed by using

ladder diagram in PLC software Codesys ENE server V2.3. The temperature control, flow and level

unit NE40UX are used where the temperature control unit is a special I/O unit that receives inputs

directly from RTDs and special I/O unit that receives inputs directly from flow sensors and level

sensor of plant. Whatever the temperature, flow, level is desired by the user in accordance with that

the set point (SP) is set by the user using the PC. In this work in addition to PLC controlling,

Cascade, Ratio and Feedback loops are also used for controlling the above mentioned process

parameters. For output control unit NE02AX is used for controlling the Input converters and control

valves etc.

Keyword: Flow Control, Level Control, PID, PLC, RTD.

INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING

AND TECHNOLOGY (IJARET)

ISSN 0976 - 6480 (Print)

ISSN 0976 - 6499 (Online)

Volume 6, Issue 1, January (2015), pp. 19-26 © IAEME: www.iaeme.com/ IJARET.asp

Journal Impact Factor (2014): 7.8273 (Calculated by GISI) www.jifactor.com

IJARET

© I A E M E



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1. INTRODUCTION

To fulfil high control performance requirements and advanced control the control engineering

methods used in industries was the proportional, integral and derivative (PID) controller that is

widely used since the last four decades. To simplify the controlling in manufacturing system, process

control system etc., Programmable logic controller (PLC) is widely used as industrial control. From

the several languages described for the PLC programming, the ladder logic is mostly used language.

In past the industries which are using automation in controlling the process Temperature, Flow,

Level, Pressure and density they use a PID controller which was based on microcontroller. After that

for better automation in controlling process of industries PLC was used. Initially the Mitsubishi PLC

was originated for on/off (discrete) process control functions, but now a day’s PLC can also operate

analog PID control functions as its speed and capability has increased. For example Nexgenie 1000

PLC of Mitsubishi can control various parameters. Codesys software is used for controlling purpose.

A computer control system consisting of PLC is designed to improve the level of automation. By

using the PC, desired temperature or set point (SP) is set by the user and the process temperature

based on the SP temperature is maintained by the controller within the PLC.

Regarding from that, the research will be divided in two parts hardware development and

software development. RTD is used as the sensor and also to measure the temperature parameter will

send the digital signal to the PLC in “ON” or “OFF” signal .The main part of this research work is

PLC which can be considered as the ‘brain’ which completely controlled the Temperature, flow and

level with the help of feedback loop, cascade loop or ratio control system.

Fig.1: PLC Design for PID Controlling.

Very complex process control such as used in the chemical industry may require algorithms

and performance beyond the capability of even high-performance PLC. Very high-speed or precision

controls may also require customized solutions. Then in this work we want to overcome the error

which occurs in other controller or in normal digital PLC. The developed controller is implemented

on a heater-furnace system and the algorithms are developed using the ladder functions of the PLC.

The benefit of this system is that it does not require any external display device which may be HMI,

any voltmeter or ammeters or any other devices, because in this all parameters are set or seen in

ladder logic program on PC.

2. PROGRAMMABLE LOGIC CONTROLLER

A PLC is a digital computer can be used for automation of electromechanical processes such

as control of machinery on amusement rides. PLC is a microprocessor based system which takes

analog or digital inputs from fields does logical calculations as per the user’s logic program and



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accordingly gives analog or digital outputs which could be used for monitoring purpose or process

controlling. PLCs can be used in many machines and industries. Since 1970’s, PLC system plays a

vital role to make human activities easy. It is a type of control system which is when applied changes

the behaviour of a system. When industrial revolution can be started, PLC from the feedback

becomes choice for manufacturing controls. There are different types of PLCs which are used in

industries according to the needs such as ALLEN BRADELY, MISTUBISHI, OMRON and

SIEMENS. The main method of PLC is ladder logic. PLC can be programmed, operated and

controlled by drawing the lines and devices of ladder diagram with a keyboard onto a display screen.

This drawing the converted into computer machine language and run as a user program. It is

basically use to control a process that involved relays. This technique is based on relay logic wiring

schematics. CoDeSys is a complete development environment for the PLC. (CoDeSys stands for

Controlled Development System).

3. PID CONTROL MODEL

There are three basic types of controllers: on-off, proportional and PID. This type of

controller can be provides proportional with integral and derivative control. These adjustments can

be integral and derivative expressed in time-based units; they can also be referred to by their

reciprocals. The proportional, integral and derivative terms can be individually adjusted or “tuned” to

a particular system using trial and error. In this the measure value is compares by PID controller with

a reference set point value. For manipulatable input the error is calculated a new value for a desired

value by feedback process. The PID controller can set process outputs depending upon the feedback

and changing rate of error signal by which the output is accurate and stable. It (PID) has mainly

application in industrial purpose, but now a day it designed for control theory and technology.

Because these has a advanced process. An example of the PID speed control system. The error signal

e can be represents the difference between the speed command and speed feedback. The proportional

control can be multiplies the speed error e by a constant Kp the integral control can be multiplies the

e by a constant Ki to correct steady state error and the derivative control can be reduces the

overshoot and the rise time or,

U(t) = Kp e(t)+ KpKi ∫o e(t)dt + KpKd de(t)/dt (1)

Where: U(t): control signal, Kp: Proportional gain, Ki: Integral gain, Kd: Derivative gain. e(t) will be

an error term ∫o e(t)dt will be a summation of all past error over time and de(t)/dt will be rate of

change of error term.

E (t ) = r(t) – y(t) (2)

Where; r (t): Set point (SP), y (t): Measured value

Fig.2: Typical configuration for a PID control system



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Temperature Control System: If the Measured variable is less than the set point, (MV < SP), it

means, that the temperature of the cold liquid OUTLET is below then that desired. It means that the

amount of heat transfer from the hot water to the cold liquid is less than that desired. There may be

two reasons for that i.e. the temperature of the Hot water may be less, or the flow of hot water may

be less and the flow of cold water may be more. The complete model is shown in Fig.3.

Fig. 3 The Proposed Model of Controller

Level Control System: A Level Capacitance Probe (LIC) senses the level of the tank. A probe

connecting to this transmits the signal. The effective level of the tank is 300mm. For this head, the

output signal range of the Level Capacitance Probe is 4-20mA. Corresponding to the level in the

tank, an electrical signal is transmitted to the Level Indicator Controller (LIC) (ex: if the level in the

tank is 150mm, then a signal of 12mA is transmitted). The controller LIC reads this value (which is

known as the measured variable or MV), compares it with the set point (SP) value. The difference of

these two values; known as the ERROR, is fed to the controller. The liquid is sucked into the Pump

P-1 from Tank T-1 and finally discharged to tank T-2 through Orifice meter (FI) if the level in the

tank T-1 is low then PCV will open up further to increase the amount of flow through it, thereby

increasing the level. If the level is higher, the controller will send a reverse signal to limit the

opening of the PCV-2 and hence to limit the flow.

Flow Control System: The working principle of turbine flow transmitter is such that if a fluid moves

through a pipe and acts on the vanes of a turbine the turbine will start to spin and rotate. The rate of

spin is measured to calculate the flow). The Turbine flow transmitter TFTx senses the flow and sends

out the signal to the controller FIC. The output signal from the TFTx to the FIC is in the range of 4-

20mA. The TFTx is calibrated in a manner; such that, the input flow range of 0-20 lpm corresponds

to an output signal of 4-20mA. The controller FIC compares this value, which is known as the

MEASURED VARIABLE or MV with the set point (SP). The difference in the two values known as

the ERROR is sent to the final Control element i.e. Pneumatic Control Valve. In this case, the final

control element is PCV. If the flow is higher than that which is desired (i.e. MV > SP), the controller

FIC will send a signal such that the output of the PCV decreases, so that the flow through it reduces.

In the reverse case, if the flow is less than the desired (i.e. MV < SP) the output of the controller is

increased such that the flow through PCV is increased.



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4. RESULTS AND DISCUSSION

The temperature control of the proposed model has been controlled using software CoDeSys

ENE server V2.3. The observation and the result obtained are shown in Table- 1 and in fig. 4.

Table - 1 Observation Table of Temperature Control System

S.

No.

Time of

Testing

Controlling

Temperature

in oC

Exact Temperature

according Thermometer

after controlling (A) in oC

Temperature which

controlling by heat

exchanger (B) in oC

Error

E=A-B

1 09.15 A.M. 19 19.07 19.01 0.06

2 10.15 A.M. 31 31.2 31.13 0.07

3 11.30 A.M. 34.2 34.28 34.21 0.07

4 01.00 P.M. 45 45.85 45.1 0.075

5 03.15 P.M. 51.5 51.65 51.57 0.08

6 10.00 A.M. 73.7 74 73.9 0.1

7 12.00 P.M. 78 78.1 78 0.1

Fig. 4 Output Error Waveform of Temperature Control System

Similarly the level control of the proposed model has been controlled using software

CoDeSys ENE server V2.3. The observation and the result obtained are shown in table - 2 and in fig.

5.

Table - 2 Observation Table of Level Control System

S.

No.

Time of

Testing

Controlling

Level in mm

Exact Level according

Level gauge after

controlling (A) in mm

Level which

controlling by PLC

(B) in mm

Error

E=A-B

1 09.30 A.M. 130.00 130.10 130.05 0.05

2 11.15 A.M. 146.20 146.30 146.24 0.06

3 12.35 P.M. 175.50 175.57 175.51 0.06

4 02.00 P.M. 195.00 195.17 195.10 0.07

5 03.15 P.M. 230.70 230.78 230.71 0.07



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Fig. 5 Output Error Waveform of Level Control System

Also the flow control of the proposed model has been controlled using software CoDeSys ENE

server V2.3. The observation and the result obtained are shown in table - 3 and in fig. 6.

Table - 3 Observation Table of Flow Control Cystem

S.

No.

Time of

Testing

Controlling

Flow in lpm

Exact Flow according Flow

gauge after controlling (A)

in lpm

Flow which

controlling by PLC

(B) in lpm

Error

E=A-B

1 09.30 A.M. 1.5 1.53 1.49 0.04

2 11.00 A.M. 2 2.04 1.95 0.045

3 12.10 P.M. 4 4.08 4.03 0.05

4 02.09 P.M. 5 5.06 5.01 0.05

5 03.00 P.M. 6.5 6.58 6.52 0.06

Fig 6 Output Error Waveform of Flow Control System



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8. CONCLUSION

In this research all parameters (temperature, flow and level) have been controlled using the

feedback, ratio and cascade loop and found out the errors as compare to the standard temperature or

flow or level as supplied. After studying the results obtained of Temperature, Flow and Level we

conclude that proposed method provides better efficiency in terms of network lifetime, speed of

controlling parameters and less error in comparison to other methods. For other controller it is quite

difficult to work for the accuracy but in this work using PLC the PID implementation increases the

accuracy of the process in a plant or system.

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Plc Based Pid Implementation in Process Control of Temperature Flow and Level