Adaptive fuzzy control for perturbed strict-feedback nonlinear systems with predefined tracking accuracy

In this paper, the tracking control problem for a class of nonlinear strict-feedback systems with disturbances is addressed. An adaptive fuzzy controller is developed by using the backstepping design technique based on a novel kind of nonnegative integral-type functions. In contrast to the existing results on the uncertain systems with additional disturbances, the features of the proposed control scheme are that it can guarantee the ultimate tracking error achieving an accuracy given a priori and the controller singularity problem is avoided completely. By introducing two novel nth-order continuously differentiable switching functions, the desired actual controller and the virtual control variables are obtained. The convergence of the tracking error is analyzed by using Barbalat’s lemma. It is shown that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded. Finally, a simulation example is given to illustrate the effectiveness of the proposed control scheme.