Fault detection and accommodation of saturated actuators for underactuated surface vessels in the presence of nonlinear uncertainties

Abstract

This paper investigates a fault detection and accommodation (FDA) problem of saturated actuators for trajectory tracking of underactuated surface vessels (USVs) in the presence of nonlinear uncertainties. A robust fault detection observer and a time-varying detection criterion are presented to detect the actuator faults distinguished from uncertainties in nonlinear dynamics and external disturbances. Then, we develop an adaptive fault accommodation scheme using the dynamic surface design to compensate the detected faults. For the fault accommodation control, the auxiliary variables and their dynamics are derived to consider the saturation problem of actuators with the nonholonomic property of USVs and to analyze the stability of the sway dynamics clearly. To ensure that tracking errors are globally uniformly ultimately bounded, the projection algorithm is employed for the design of the bounded virtual and actual control laws. The effectiveness of the proposed FDA system is demonstrated by simulation results.