Adaptive fuzzy controller for a class of strict-feedback nonaffine nonlinear systems

A robust adaptive fuzzy control scheme is presented for a class of strict-feedback nonaffine nonlinear systems with modeling uncertainties and external disturbances by using a back-stepping approach. Fuzzy logic systems are employed to approximate the unknown parts of the desired virtual controls, and the approximation errors of fuzzy systems are only required to be norm-bounded. The function tanh(·) is introduced to avoid problems associated with sgn(·). The tracking error is guaranteed to be uniformly ultimately bounded with the aid of an additional adaptive compensation term. Chua's circuit system and Rössler system are presented to illustrate the feasibility and effectiveness of the proposed control technique.