Adaptive tracking control of uncertain constrained nonlinear systems with input saturation

In this paper, the adaptive tracking control problem is investigated of uncertain nonlinear systems with input saturation, asymmetric state-function constraints and unknown control gains (UCG). The hyperbolic tangent function is used to deal with input saturation, and the original system is equivalent to a new system with explicit control input. Nussbaum function and fuzzy logic system (FLS) are simultaneously employed to process UCG and uncertain nonlinear functions, respectively. Integrating the barrier Lyapunov function (BLF), a new adaptive fuzzy controller is designed to ensure that all the signals of the closed-loop system are bounded and the states do not violate asymmetric function constraints. Meanwhile, the tracking error converges near the origin. Finally, the availability of the proposed control scheme is demonstrated by two examples.