Adaptive fuzzy control for a class of uncertain nonlinear systems with unknown nonsymmetric dead-zone input

In this paper, an adaptive fuzzy tracking control algorithm is discussed for a class of strict-feedback nonlinear system with non-symmetric dead-zone inputs without considering traditional back-stepping technique. We introduce some new variables and coordinate transforms to convert the strict-feedback form into normal form, and the new states variables are not directly measurable, therefore, an observer needs to be designed to estimate the indirect un-measurable states and the control can be realized without back-stepping scheme. Based on Lyapunov theorem analysis, the designed fuzzy controller can make sure that all the signals in the closed-loop system are uniform ultimate bound-ness and can compensate the effect of unknown dead-zone, at the same time; it has a simple form with only two adaptive parameters to be updated on-line. This proposed control algorithm is considerably simpler than the traditional back-stepping-based ones. Simulation results are presented to verify the effectiveness of the proposed approach.