Thruster fault-tolerant control for dynamic positioning of vessels

This paper proposes a fault-tolerant control (FTC) scheme for dynamic positioning (DP) of vessels under thruster faults. A fault state observer is constructed to estimate the unknown fault states. An integrated FTC design method based on the fault state observer is presented for the DP system using the dynamic surface control (DSC) approach. Furthermore, the FTC forces and moment computed from the designed FTC law are allocated to individual thrusters through applying the Lagrange multiplier method. By means of Lyapunov functions, it is proved that the FTC law can maintain the vessel position and heading at the desired values, while guaranteeing the uniform ultimate boundedness of all signals in the closed-loop DP FTC system of vessels under thruster faults. Finally, simulation studies on a 1:70 scale model of a supply vessel are carried out to demonstrate the effectiveness of the proposed FTC scheme.