Fuzzy adaptive control of nonlinear uncertain plants with unknown dead zone output

Abstract

This paper focuses on a tracking problem for a class of strict-feedback nonlinear systems with unknown dead-zone output and unmeasurable states. Based on the adaptive backstepping technique, a new adaptive fuzzy control scheme is proposed. It is shown that the proposed control scheme guarantees that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded, the tracking error converges to a small neighborhood of the origin. Moreover, the proposed control method requires only one adaptive law for an nth-order system and the structure of the controllers is very simple, so they are easy to be implemented. The main advantage of this paper is that the unknown dead-zone nonlinearity in the output mechanism of strict-feedback systems is considered. By introducing a Nussbaum function, the problem of unknown virtual control coefficient is resolved, which is caused by the nonlinearity in the output mechanism. Finally, simulation results are provided to show the effectiveness of the proposed approach.