Event-triggered adaptive fault estimation and fault-tolerant control for strict-feedback nonlinear systems with full state constraints

This paper addresses the problem of event-based adaptive fault estimation and fault-tolerant control for a class of strict-feedback nonlinear systems with full state constraints. The unknown fault and the to-be-tested states of the system are estimated by an innovative adaptive fault observer based on a modified intermediate variable update law with fault switching function. In addition, an event-triggered mechanism and adaptive fault-tolerant controller co-design scheme is proposed according to backstepping algorithm and constrained technique, which not only eliminates the effect of fault presence but also leads to a significant reduction of communication resources. Through theoretical analysis, the constructed controller ensures that all signals within the system are ultimately bounded, and the state errors converge to the desired neighborhoods. Finally, the effectiveness of the method is illustrated by a simulation example of a single-link robot system.