Hybrid Fuzzy Control of a Class of Nonlinear Systems

In this paper, a hybrid fuzzy controller based on a fuzzy proportionalintegral plus conventional derivative control structure is proposed to control a class of single-input single-output nonlinear systems. The proposed controller is capable of generating both linear and nonlinear outputs so that the closed-loop system is equivalent to a feedback connection of a linear system and a nonlinear element in the error state space. It is shown that absolute stability of the closed-loop system can be guaranteed if the nonlinear output of the fuzzy controller is bounded by virtue of the circle criterion. The proposed controller is used to control an inverted pendulum and the performance is shown to be superior.