The Design And Realization Of Fuzzy-PID Water Level Control System

PID controller has simple structure and good robustness and it is widely used in process control systems. Conventional PID can not regulate itself according to the changes on-line, so the Conventional PID control of nonlinear systems 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. Fuzzy control has got good effect in many industrial applications, but it has steady errorness. The combination of fuzzy controller and PID controller has certain practical values in the application of liquid-level control system.In this paper, fuzzy and conventional PID control are combined and used in water level control system.Firstly, we build a model of water tank of liquid level control system by using the method of experiment, and have designed the liquid-level control system. Secondly,setting suitable membership function and design the fuzzy control rule,and design the fuzzy controller,and analysis what the quantification of error,the rate of error change,and the change of output influence on for the informence of control system, respectively. Setting suitable membership function and design the fuzzy-PID control rule,and design the fuzzy-PID controller.Thirdly,designing the liquid level cascade control system use the tool of MATLAB/Simulink,with the fuzzy-PID controller as the main regulator and the proportional controller as the auxiliary regulator. When the math plant of control object of liquid level control system,the fuzzy-PID controller,fuzzy controller and PID controller are used as main regulator respectively,comparing the performance of liquid level control system. Fourthly, the algorithm of conventional PID control ,fuzzy control and fuzzy-PID control have been carried out for the experiment equipemt of liquid level control system respectively.We have configurated the liquid control system by the configuration software of MCGS and realized the control algorithm in MCGS by programming. What the controlling result in experiment have testified the performance of fuzzy-PID controller.It is better than PID controller and fuzzy controller for liquid level control system..