A nonlinear fault-tolerant thruster allocation architecture for underwater remotely operated vehicles

:This paper proposes an actuator failure tolerant robust control scheme for underwater Remotely Operated Vehicles (ROVs). A reduced order observer has been introduced for estimating the ROV velocities and a sliding mode control law has been developed using the available position measurements and the velocity estimates provided by the observer to achieve output regulation. A thruster failure is shown to be detectable simply checking the presence of any deviation of the observed sliding surfaces. Moreover, an isolation policy for the failed thruster is proposed. Finally, control reconfiguration is performed exploiting the inherent redundancy of actuators with the implementation of an adaptive input allocation architecture. An extensive simulation study has been performed, supporting the effectiveness of the proposed approach.