Predefined performance fuzzy adaptive tracking control for nonlinear stochastic systems with input saturation

In this paper, the problem of adaptive fuzzy output feedback tracking control is investigated for a class of single-input and single-output nonlinear stochastic systems with prescribed performance, input saturation and unmeasured states. Fuzzy logic systems are used to identify the unknown nonlinear system, the input saturation is approximated by a smooth function, and a fuzzy state observer is designed for estimating the unmeasured states. Based on the backstepping recursive design technique and the predefined performance technique, a new fuzzy adaptive output feedback control method is developed. It is shown that all the signals of the resulting closed-loop system are bounded in probability and the tracking error remains an adjustable neighborhood of the origin with the prescribed performance bounds. A simulation example is provided to show the effectiveness of the proposed approach.