Event-triggered backstepping optimal fault-tolerant tracking control for strict-feedback nonlinear time-delay systems

This paper focuses on the event-triggered optimal fault-tolerant tracking control problem for strict-feedback nonlinear systems subject to both unknown time delays and non-affine nonlinear faults. Based on a novel identifier-critic-actor framework of the adaptive dynamic programming (ADP) algorithm and the optimised backstepping technique, an event-triggered optimal fault-tolerant tracking control method is obtained such that the closed-loop error tracking system is semi-globally uniformly ultimately bounded (SGUUB) under restricted communication resources, time delays, and faults. To regulate the identifier-based uncertainty compensation, an adaptive authority allocation mechanism is introduced to determine the weight of the identifier-based uncertainty compensation in the control law according to the online identifier reliability and the current tracking demand. Besides, simplified neural network (NN) update rules are derived from the negative gradient of a simple positive function related to the Hamilton-Jacobi-Bellman (HJB) equation. Finally, the effectiveness of the proposed control method is validated through simulation studies, which show improved tracking performance and less resource consumption than existing methods.