Implementation of PID for Temperature Control Using PLC

The purpose of the automatic control is to be applied mechanisms of operation without constant human interactions.  With a growing demand for control of industrial processes, an effective and efficient method is needed.  In most industrial processes, some specific variables are i

Project Title

Implementation of PID for Temperature Control Using PLC

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

The purpose of the automatic control is to be applied mechanisms of operation without constant human interactions.  With a growing demand for control of industrial processes, an effective and efficient method is needed.  In most industrial processes, some specific variables are important and should be set around a few desired values. For example, the temperature in a chemical process is important to maintain consistent performance. Currently, most temperature control systems use automatic control technology that improves the degree of device automation and control accuracy. It is meaningful to conduct such an experiment to simulate the common control problem. Whatever the process or parameters (temperature, flow, speed, ...) the control principles are similar. The control of a process is done via a closed-circuit i.e. the feedback system.

The smooth operation of the device is always a requirement in industries. Temperature chambers are is one of the most used and critical parts that need to be controlled in the industries.  Programmable Logic Controller (PLC) is a core device that controls all the devices in the conventional industry but PLC works only on binary logic (ON/OFF). For smooth operation in many cases especially temperature control where the challenges like overshoot, rise time, and steady-state error are critical; an algorithm known as Proportional Integral Derivative (PID) is required that helps in controlling the ON time and OFF time to deal such challenges. The PLC is a hardware that is physically connected with the devices and PID is an algorithm that enables the PLC to provide the desired command to the devices. An interactive Human-Machine Interface (HMI) will also be developed to enable the operator to monitor/control the overall system.

The main goal of our project is the “Implementation of PID controller for temperature control of water using a programmable logic controller (PLC)”. This project is based on Industrial automation and has vast applications in many industries like milk industries, chemicals, food, mineral water, and many other industrial manufacturing processes. A prototype consisting of a liquid chamber with a heating element and a temperature sensor will be constructed. The PLC will maintain the temperature of the chamber according to the set point as set by the user using the Human Machine Interface (HMI). A complete analysis using a variety of PID parameters in response to the system will be presented. The performance of the controller is evaluated in terms of settling time, rise time and percent overshoot. 

Project Objectives

1. Mathematical modeling of the temperature control system.
2. Implementation of PID in PLC to provide input to the system while taking into consideration the output of the system as well.
3. Development of Human Machine Interface for controlling and monitoring.

Project Implementation Method

The PLC reads and processes the input from the input field devices (temperature sensor and ADC module that provide input to the PLC) according to the program burned in PLC and gives control signals to solid-state relay which in turn operates the output field device (Immersion Heater) to control the process. Human-Machine Interface (HMI) is a user interface or a dashboard that connects a person to a machine to control/monitor an industrial system. HMI is used to enhance user efficiency and reduce training and skill requirements. The block diagram of the overall system is shown in figure 1;

                                               

                 Fig1.Block Diagram

Software Implementation:

WinProladder software will be used to build the ladder logic of our project. 

Mircosoft VISIO software is being used for flowcharts, block diagrams, etc.

Easybuilderpro software used to develop the Human Machine Interface.

Hardware implementation:

FATEK PLC (FBs-32MAR) Used as Programmable Logic Controller.

FBs-2TC Module Expansion module used for the temperature sensor(thermocouple).

Thermocouple sensor (K-Type) Used for temperature measurement

Solid State Relay ON/OFF Heater when some external voltage is applied.

Immersion Heater It is a device which is installed in a tank to heat a liquid

Heating Tank It contains the liquid.

Benefits of the Project

• An automation system is developed for industrial process control.
• Automated system to reduce human efforts, wages of labor and increase in production rate.
• The system becomes user-friendly with the Human Machine Interface (HMI) design.

Technical Details of Final Deliverable

PID controller is implemented by using ladder logic in FATEK PLC FBs-32MA. For PID control, the control unit takes input from the thermocouple sensor and performs the control action. A setpoint (SP) is provided by the user using a human-machine interface and the controller within the PLC will try to maintain the current temperature based on the set point. Programmable Logic Controller (PLC) reads the temperature value from the thermocouple sensor(k-type) and calculates the difference between the current value and desired value that is known as error. Then this error is provided to the PID function block which will set the value of duty cycle or decide the ON/OFF time of the solid-state relay. The PLC will provide a signal to the solid-state relay to actuate the immersion heater to heat the water. The thermocouple sensor measures the current temperature of the water and produces the output voltage corresponding to the provided input. The output voltage is in the analog form which is converted into digital through analog expansion module FBs-2TC. The digital output of the FBs-2TC module is provided as input to the PLC to achieve the desired temperature value. The process diagram is shown in figure 2.

                                                                     Fig. 2 Process Diagram

The temperature control is a closed-loop process. The PID parameters are updated each time the PLC receives the reading from the temperature sensor to reach a set point. Once the setpoint is reached it continuously reads the sensors reading and sets the PID parameters such that to maintain the required temperature in the chamber. A basic mechanism is presented in the flow chart given in figure 3.  

                                                                  Fig. 3 Flow Chart

Final Deliverable of the Project

HW/SW integrated system

Core Industry

Food

Other Industries

Manufacturing

Core Technology

Others

Other Technologies

Sustainable Development Goals

Clean Water and Sanitation, Decent Work and Economic Growth, Industry, Innovation and Infrastructure, Responsible Consumption and Production

Required Resources

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