Adaptive fuzzy tracking control for a class of uncertain nonaffine nonlinear systems with dead-zone inputs

This paper considers the problem of adaptive fuzzy tracking control for a class of uncertain nonaffine nonlinear systems with mismatched external disturbances, parameter uncertainties, and nonsymmetric dead-zone inputs. Without the help of the dead-zone inverse function and by incorporating the implicit function theorem, both the adaptive state feedback tracking controller and the adaptive output feedback tracking controller based on high gain observer are designed by utilizing fuzzy logic systems (FLS) to approximate the appropriate nonlinear control input functions. A compounded disturbance is defined in terms of the external disturbance, parameter uncertainty, nonsymmetric dead-zone input, and approximation error of FLS. Under the condition that the upper bound of the compounded disturbance is unknown, novel adaptive laws are introduced to estimate and tune the unknown controller parameters on-line. Furthermore, on the basis of Lyapunov stability analysis, it is also proved that the presented control methods can guarantee that all the closed-loop system error signals are uniformly ultimately bounded. Finally, two simulation examples are provided to demonstrate efficiency of the proposed adaptive fuzzy tracking control approaches.