Adaptive Dynamic Surface Fuzzy Control for State Constrained Time-Delay Nonlinear Nonstrict Feedback Systems With Unknown Control Directions

This article proposes an adaptive dynamic surface fuzzy control method for a class of nonstrict feedback systems. The systems are subject to state constraints with unknown control directions, time-delay, and external disturbances. The problem of unknown control direction is solved by using the Nussbaum gain technique, and the effect of unknown delay which is time varying is eliminated by introducing compounding type Lyapunov function. Furthermore, based on the fuzzy backstepping method, an adaptive tracking controller is constructed which guarantees that the constrained states are not violated while all the closed-loop trajectory signals remain bounded. The effectiveness of the obtained results is illustrated via simulations.