Interval Type-2 Sliding Mode Fuzzy Controller with a Time-varying Sliding Surface

Sliding mode control is a nonlinear, deterministic, robust control method and treated as a subclass of variable structure systems theory. The control input is obtained with a high speed, nonlinear feedback that drives the phase trajectory to a predetermined or adaptive sliding surface and then the control input discontinuously switches on this surface. It is easy to apply and quite effective against external disturbances and parameter variations. Thus sliding mode control has wide acceptance in the literature and application to various areas. Fuzzy logic, on the other hand, is a general-purpose method that uses the experience and perception of the human expert of a process. In this study dynamic, deterministic, continuous-time, nonlinear, lumped parameter second-order systems are considered. The main objective of this study is to develop a novel interval type-2 sliding mode fuzzy controller with a time-varying sliding surface. The variation of the sliding surface with respect to time is performed by a coordinate transformation. The conventional sliding mode controller, type-1 sliding mode fuzzy controller and the proposed interval type-2 sliding mode fuzzy controller have been applied to a mass-spring-damper control problem. The simulated results are evaluated and the results verified the efficacy of the proposed interval type-2 sliding mode fuzzy controller.