Fuzzy Control Technique In Process Control

Since Prof. L.A.Zadeh of California University established the "Fuzzy Set" theory in 1965 and E.H.Mamdani firstly successfully applied the fuzzy control technology to the boiler and the steam engine control systems in 1974, the fuzzy control technology has been developed quickly and applied widely in control project. The fuzzy control technology therefore has the so formidable vitality, is because it has the merit which other control methods cannot be substituted: First is it needs not the precise mathematical model of the controlled object; Second is its fast controlling speed, good robustness, fuzzy control's rising character is better than other control methods, this point is close to person's response, although the person is not very sensitive to the slight change, they can fast and accurately judge and control to the big change; Third is fuzzy control technology itself has the forecast function, this function may manifest from the fuzzy control rule. The fuzzy control rule originates from expert's experience knowledge. Any expert has full estimate and forecast to the future when they formulates some plan and control strategy, thus we can say fuzzy control itself has the forecast function, this spot will compare to other control methods is most commendable.But fuzzy control also has its own flaw: First, mathematics mechanism is not very clear, generally speaking the fuzzy control fundamental research is falls behind its application. Second, the fuzzy control's core partial - controls rule, excessively relies on expert's experience knowledge, if be short of expert's experience, or has not the entire experience, then this fuzzy controller's control rule has the loophole and maybe appear the unexpected result. Third, the fuzzy control's precision is not high. The main reason is the fuzzy control static error and the zero vibration, which has directly restricted it in the high accuracy control domain application. This article has done some exploratory work for these questions, specifically as follows:1.The design of auto-adjusted fuzzy controller and the rule auto-adapted fuzzy controller. In the fuzzy control system, the performance is decided greatly by the fuzzy control rule and related parameter. Regarding the general control system, the performance is not ideal with the same fuzzy control rule as well as group of fixed invariable parameters, The paper has separately discussed two design methods of auto-adjusted proportion parameter Ku fuzzy controller and the rule auto-adapted fuzzy controller, the experiment indicated that, the control effect is good.2.Eliminating static error, increasing the control precision. While we explore the new control method, we shouldn't neglect the traditional control method's merit. Unifying the fuzzy control and other control methods is good research way in field ofmodern intelligence control. The paper has discussed two methods of unifying the fuzzy control with PID and the intelligent integrator. We obtain the very good control effect in the experiment.3.The application of fuzzy control in the MIMO system. Current literatures about the application of fuzzy control mostly all concentrate in the SISO system. Actually the fuzzy control's bigger superiority is applied in the MIMO system. The paper has discussed fuzzy controller's characteristic of eliminating coupling, and pointed out its merit by an example.