Adaptive fuzzy output-feedback control for output constrained nonlinear systems in the presence of input saturation

In this paper, the problem of adaptive fuzzy output-feedback control is investigated for a class of output constrained uncertain nonlinear systems with input saturation and unmeasured states. To address output constraint and input constraint, a barrier Lyapunov function and an auxiliary design system are employed, respectively. Fuzzy logic systems are utilized to approximate the unknown nonlinear functions, and a fuzzy state observer is designed to estimate the unmeasured states. By utilizing the fuzzy state observer, and combining the adaptive backstepping technique with adaptive fuzzy control design, an observer-based adaptive fuzzy output-feedback control approach is developed. It is proved that the proposed control approach can guarantee that all the signals in the closed-loop system are bounded, and the input and output constraints are circumvented simultaneously. A numerical example is provided to illustrate the effectiveness of the proposed approach. (C) 2013 Elsevier B.V. All rights reserved.