Robust adaptive fault tolerant control for a steering subsystem of unmanned underwater vehicles

This paper deals with the robust adaptive fault-tolerant compensation control problem for steering subsystem of unmanned underwater vehicles (UUVs) with actuator time-varying faults, disturbances and parameter uncertainties. A sufficient condition for the existence of reduced-order sliding mode dynamics is derived in the case of actuator faults, and an explicit parametrization of the desired sliding surface is also given. Without the need for a fault detection and isolation (FDI) mechanism, an adaptive sliding mode controller is developed based on the online estimation of an eventual fault to maintain the sliding mode, where the gain of the nonlinear unit vector term is updated automatically to compensate the effects of actuator faults and exogenous disturbances. The simulation demonstrates the effectiveness of the proposed design method.