Adaptive fuzzy output-feedback control with unknown dead-zone and high-frequency control gain sign

A robust adaptive output-feedback control scheme is proposed for a class of nonlinear systems with unknown dead-zone and high-frequency control gain sign. The design is based on the approximation capability of the first type fuzzy systems. Combining the Nussbaum gain technique with adaptive backstepping method, the high-frequency control gain sign is assumed to be unknown. By employing the tuning functions, the adaptive law is designed, and the overparametrization is avoided. Furthermore, using the Youngpsilas inequality and parameter adaptive estimation, the parameters of the dead-zone model and the upper bound of the disturbances neednpsilat to be known. By theoretical analysis, the closed-loop control system is proved to be uniformly ultimately bounded (UUB). Simulation results demonstrate the effectiveness of the approach.