Adaptive Fuzzy Tracking Control for Nonlinear Time-Delay Systems With Performance Constrained by Deferred Monotone Tube Boundaries

This article presents an adaptive fuzzy output-feedback control method for a class of nonlinear time-delay systems with prescribed tracking performance. Based on proper tuning functions and a pair of monotone tube boundary functions, a novel error transformation is proposed, which can constrain the tracking error within predefined monotone tube boundaries provided that the transferred variable is bounded. To this end, an adaptive output-feedback controller is designed to stabilize the transferred variable. We use fuzzy logic systems and adaptive control techniques to approximate the unknown nonlinear functions, and a reduced-order observer with less dynamics is proposed to estimate the unmeasurable state. In order to reduce the computation burden, we adopt command-filters method, which can avoid the complexity explosion problem in backstepping controller design procedure. Our article presents a way to constrain the tracking error with improved performance indices, such as overshoot, and convergence time. In addition, the method is independent of the initial values. Numerical simulations are given to verify the effectiveness of the proposed approach.