Industrial temperature control system

An industrial temperature control system is a system that is used to regulate the temperature in industrial settings such as factories, warehouses, and power plants. This type of system can be used to control the temperature of a wide variety of processes, including heating, cooling, and temperature-sensitive manufacturing processes. The system typically includes sensors that measure the temperature, a control unit that processes the temperature data and sends commands to the heating or cooling equipment, and actuators that adjust the temperature by controlling the flow of heat. The system can be operated manually or automatically, and it can be integrated with other systems such as building management systems to provide a holistic approach to temperature control. 

System design

In this design, the temperature control system consists of hardware and software components. 

System hardware

In the hardware part of the system, the acquisition module uses the temperature sensor to measure the measured object temperature, and the temperature signals are converted into electrical signal , which are then transmitted to the temperature transmitter, where the electrical signal is converted into a 4 ~ 20mA current signal, so that the module EM235 in the PLC expansion module can be facilitated as to the analog signal input. EM235 receives data, which will be sent directly to the PLC output control text display (display temperature) and the temperature control device (heating &cooling device). The system block diagram is shown image:

 System software

The software of this system adopts STEP7 for PLC200, the popular programming software by Siemens, for software compilation , and the temperature controller device adopts fuzzy PID algorithm for temperature control, with the simulation to be implemented by MATLAB simulation software.
image shows that the system consists of four modules, i.e., acquisition module, control module, display module and implementation module. The acquisition module includes PT100 temperature sensor and temperature transmitter. PT100 temperature sensor works with a temperature variable that can be converted into a standardized output signal. This instrument is mainly used for industrial process with measurement temperature and control parameters. The temperature transmitter is a signal conversion device, which is responsible for the signals collected by the temperature sensor to be converted to electrical signals of 4 ~ 20mA. This is quite convenient for PLC200’s identification and collection of temperature signal. For control module, Siemens PLC200 is chosen as the core controller, playing the role of the completion of the temperature signal collection, signal processing and signal transmission. Display module using TD200 text display can be better compatible with the PLC to complete the data transmission. This display module displays the current temperature and the desired temperature. Implementation module works by using cold fan and heating resistor, through the PLC-controlled cold air fan and heating resistor to complete the instructions for the temperature rise or fall, and finally, the temperature reaches a constant value.

 Software design

According to the system design requirements, the software program flow is shown in Image.
First of all, the parameters of the temperature control system undergoes wake-up initialization, mainly to set the control temperature and the PID initial value, including the value settings of PID gain, PID integral time, PID differential time and PID sampling time. Then, the ambient temperature is collected through the sensor in a range of 6400 ~ 320000, as the digital signal. As the fuzzy PID algorithm requires real-format temperature signal input, there is the need for A/D conversion of temperature signal prior to the PID algorithm process. The collected digital signal is converted into double integer signal, which is then transformed into a real figure. The actual temperature is calculated by the temperature calculation formula. The measured temperature is taken as the input signal for PID operation, and the output is ready for the control of the heating resistance and cold air fan. In the design, the temperature control is based on the PID control algorithm. PID is the most commonly applied in industrial production, a control method being able to meet the need for high-precision measurement and control systems.Using PID algorithm to achieve the temperature control system can be more stable and reliable .

 Experiment and Simulation

Assume that the system has an open-loop transfer function as G (s) = 1/S (2*S + 5), and a fuzzy control system is established in Matlab, as shown in Figure 4. At this time, the amplifier Gain = -1000, Gain1 = 0.05, Gain2 = 0.01. Select the controlled object and its reference model, and we can get the simulation curve shown:

 Simulation Results of Fuzzy Control System:


In this work, the temperature control system can display the temperature inside the box in real time. The temperature is adjusted by the fan and the heating plate, and the PID control algorithm is introduced to control the temperature of the cabinet to meet the temperature control needs. Using Siemens PLC200 as the controller, the system has high control precision, is stable and reliable, and is not easily affected by external interference. On-site debugging shows that the system can successfully control the temperature of the box. This work is expected to have a good application prospect.

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