The Design Of PLC Based Liquid Level Fuzzy Control System

PID controller has a simple structure and good robustness and it is widely used in process control systems, but conventional PID can not be easily regulate itself according to the changes , so the conventional PID control can not get satisfying controlling result.Fuzzy control , which is based on knowledge and independent of accurate mathe model , brings a new way of resolving this problem.In this thesis, firstly , we build a model of water tank of liquid level control system by using the method of experiment , and have designed the two-loop cascade control system, with the fuzzy controller as the main controller and the P controller as the subregulators is designed. Secondly, for the liquid level control system, the fuzzy controller is designed after appropriate membership functions and fuzzy control rulers, and the fuzzy control table is calculated. Finally , the simulations of the designed cascade system are carried out in Matlab/Simulink environment.The performances of conventional PID controller and fuzzy control are compared.In this thesis , based on the simulations, experimentations are carried out on THJ-2 equipment. By S7-300 PLC control system and configuration software STEP7V5.2 designed conventional PID and fuzzy control algorithm. The control system is watchted by the configuration software WinCC5.0. The real control results show that the fuzzy controller has good control performance...