Nussbaum Gain Adaptive Control for Nonlinear Systems with State Constraints and Input Saturation

To deal with a class of uncertain nonlinear systems with time-varying full state constraints, input saturation and unknown control direction, a Nussbaum gain adaptive control scheme is provided in this paper. Time-varying asymmetric barrier Lyapunov functions (TVABLFs) are employed to prevent the transgression of state constraints. An auxiliary subsystem is utilized to analyze the effect of input saturation. Nussbaum gain technique is introduced to compensate the influence of unknown control direction and nonlinear terms arising from input saturation. It is shown that all the closed-loop signals are bounded in the semiglobal sense, error signals converge to bounded compact sets around origin, and time-varying full state constraints and input saturation aren't violated. The effectiveness of this method is indicated by a simulation example.