MCE-based Direct FTC Method for Dynamic Positioning of Underwater Vehicles with Thruster Redundancy

Abstract

This paper presents an active, model-based FTC (fault tolerant control) method for the dynamic positioning of underwater vehicles with thruster redundancy. Unlike conventional appraoches that rely heavily on state and parameter estimation, the proposed scheme directly utilizes the vehicle’s motion control error (MCE) to construct a residual for detecting thruster faults and failures during the steady state operation of the control system. One of the primary challenges in thruster fault identification is the unavailability of the actual control input under fault conditions. However, by conducting a detailed and rigorous analysis of the MCE variation trends associated with thruster faults, valuable information about this unknown control input can be extracted. This insight forms the foundation of the proposed FTC strategy. As for control reconfiguration, it’s straightforward since the thrust losses can be directly estimated through the fault identification process. Numerical studies with the real world vehicle model are carried out to validate the effectiveness of the proposed method.