Adaptive Control for Nonlinear State-Constrained Systems with Time-Varying Delays and Unknown Control Direction

This paper presents an adaptive tracking control strategy for nonlinear state-constrained systems subject to time-varying delays and unknown control direction. In the backstepping process, the challenges of time-varying full state constraints and time-delays are solved by combining the time-varying barrier Lyapunov functions (BLFs) with the Lyapunov-Krasovskii functionals (LKFs). The Nussbaum function and neural networks (NNS) are used to handle the unknown control direction and approximate the unknown functions, respectively. The satisfactory tracking performance can be achieved without violating state constraints under our presented control method. Finally, the simulation study is implemented to illustrate the feasibility of the presented method.