DESIGN OF A FUZZY CONTROLLER WITH FUZZY SLIDING SURFACE

Fuzzy logic controllers have succeeded in many control problems that the conventional control theories have difficulties to deal with. However, the design of the fuzzy logic controllers depends to a large extent on the expert's knowledge or on trial and error. Moreover, due to the linguistic expression of the fuzzy controller, it has not been easy to guarantee the stability and robustness of the fuzzy control systems. To overcome these drawbacks, we propose to design a fuzzy controller with the fuzzy sliding surface. The fuzzy rules are defined based on this fuzzy sliding surface, and the output of the fuzzy controller is inferred by the proper compositional rule of inference. Then we show the stability of this fuzzy control system and the boundedness of the tracking error by using the Lyapunov theory. Finally, we apply this fuzzy controller to control a nonlinear time-varying system and confirm the validity of the controller.