Robust fault–tolerant tracking with predefined performance for underactuated surface vessels

• A prescribed performance design methodology for underactuated surface vessels is firstly developed in this paper.
• The proposed FTT scheme is simply designed without employing the adaptive technique to compensate for uncertainties and requiring the repeated differentiation of virtual controllers.
• The proposed approach can ensure transient performance at the moments when unknown multiple faults occur.

This paper investigates a robust fault–tolerant tracking (FTT) problem of uncertain underactuated surface vessels (USVs) with unknown faults in nonlinear dynamics and saturated actuators. All nonlinearities, external forces, and faults in USVs are assumed to be unknown. Compared with the existing literature, the main contribution of this paper is to present a predefined performance design methodology for FTT of USVs that are nonholonomic systems. The predefined performance bounds, which characterize the convergence rate, maximum overshoot, and steady-state response of control errors, are integrated with error surfaces in consideration of underactuated constraints. A new FTT control scheme using the integrated error surfaces is designed without applying any function approximators to estimate unknown nonlinearities including faults and requiring the repeated differentiation of virtual controllers where auxiliary variables are derived to ensure the predefined performance of underactuated systems. Thus, compared with the previous controllers for USVs, a simple controller design can be derived regardless of unknown nonlinearities, their faults, and actuator faults. It is shown that tracking errors are preserved within bounds guaranteeing predefined transient and steady-state performance.