Adaptive fuzzy output feedback control of uncertain nonlinear systems with unknown backlash-like hysteresis

In this paper, the problem of adaptive fuzzy output-feedback control is investigated for a class of uncertain nonlinear systems with unknown backlash-like hysteresis and unmeasured states. The fuzzy logic systems are used to approximate the nonlinear system functions, and a fuzzy state observer is designed to estimate the unmeasured states. By utilizing the fuzzy state observer, and combining the adaptive backstepping technique with adaptive fuzzy control design, an observer-based adaptive fuzzy output-feedback control approach is developed. It is proved that the proposed control approach can guarantee that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded (SUUB), and both observer error and tracking error can converge to a small neighborhood of the origin. Two simulations are included to illustrate the effectiveness of the proposed approach.