Multimodal event-triggered finite-time prescribed performance control for USVs subject to intermittent actuator faults

This paper examines fault-tolerant control for underactuated surface vessels with intermittent actuator faults. A basic control law is developed by combining the backstepping method with finite-time control, so as to improve the transient recovery capability during fault switching. A Nussbaum-type dynamic gain is incorporated to accommodate the unknown multiplicative actuator effectiveness. This design avoids explicit estimation or inversion of the time-varying actuator effectiveness factor during intermittent fault switching. A prescribed performance function is introduced to impose explicit constraints on the transient evolution and steady-state accuracy of the tracking errors. A multimodal event-triggered mechanism is designed to adaptively adjust the control update frequency according to the degree to which the tracking error approaches the prescribed performance boundary. The proposed control scheme ensures that all closed-loop signals remain bounded. The tracking errors always remain within the prescribed performance boundaries, and Zeno behavior is effectively avoided. Simulation results verify the advantages of the proposed method under intermittent actuator faults.