Prescribed performance adaptive fuzzy output-feedback dynamic surface control for nonlinear large-scale systems with time delays

The adaptive fuzzy decentralized output-feedback control method is proposed for a class of nonlinear large-scale systems. The considered nonlinear systems contain unstructured uncertainties, unknown time-varying delays, and immeasurable states. Fuzzy logic systems are used to approximate the unstructured uncertainties, and a fuzzy state observer is designed to estimate the unmeasured states. Based on the backstepping recursive design technique and the prescribed performance technique, a new adaptive fuzzy output-feedback control method is developed. In order to overcome the problem of "explosion of complexity" inherent in the backstepping control design, the dynamic surface control (DSC) technique is introduced into the control scheme. Based on Lyapunov-Krasovskii functional, it is proved that all the signals in the closed-loop system are bounded and the tracking errors remain an adjustable neighborhood of the origin with the prescribed performance bounds. The simulation examples and comparison with the previous control methods are provided to show the 'effectiveness of the proposed control approach. (C) 2014 Elsevier Inc. All rights reserved.