Control And Implementation Of PLC-based Quasi-isothermal Heat Exchanger System

This thesis deeply studies the application of fuzzy PID control in the waste heat utilization of flue gas. We proposed in this thesis a new quasi-isothermal heat exchanger system which is based on Siemens PLC. This system is based on PLC equipment and uses fuzzy theory and PID control method. By a combination of PLC, IPC, and configuration software, we can construct and implement this system.To adjust parameters in traditional PID control system, we need to get the mathematical model of the controlled object. However, the lag of control process, the nonlinear control parameter and its high-order all increases the difficulty in adjusting the Kp, Ki, Kd parameters and achieving dynamic adjustment in control process.Therefore, this thesis introduces fuzzy sets and fuzzy reasoning theory, and constructs a intelligent fuzzy PID controller by combining traditional PID control and fuzzy control. Fuzzy controller is the core of thee fuzzy control system. Fuzzy control system is an intelligent control system which has fast system response, small overshot, short transition time and some other advantages. In the basis of traditional PID controller, we add in fuzzy sets theory to dynamically change the PID parameters according to the deviation and the deviation changes. Obviously, this is more in line with the real control law of controlled object, and it can make fuzzy control be more widely used.In this thesis’first part we first introduce the background, the signature and the research status of domestic and foreign countries. Then we describe some professional knowledge related to the fuzzy PID-based quasi-isothermal heat exchanger system, such as fuzzy sets, fuzzy reasoning and PID control and so on. On this premise, we propose a system model which is based on PLC and fuzzy PID control and describe in detail its construction process. Finally, according to the model proposed before, we achieve the control and simulation of this quasi-isothermal heat exchanger with the use of PLC programming, PLCSIM and WinCC software.