Robust adaptive fuzzy control for a class of uncertain nonlinear systems

A novel scheme of direct robust adaptive fuzzy control for a class of strict-feedback uncertain systems with both unknown virtual control gain functions and unknown nonlinearities is proposed in this paper. By utilizing the approximation capability of fuzzy systems, backstepping technique and integral-type Lyapunov function, each virtual control and the adaptation law of the adjustable parameters in the fuzzy systems are determined in turn. Finally, the control law is determined. In order to improve the control performance of the closed-loop system, the unknown fuzzy reconstruction error bound is adaptively tuned on line. By Lyapunov method, the closed-loop control system is shown to be uniformly ultimately bounded. Simulation results show the effectiveness of the proposed approach.