Dual-Loop Adaptive Integral Terminal Sliding Mode Fault-tolerant Control for Unmanned Marine Vehicles

This paper addresses a dual-loop fault-tolerant control (FTC) method based on integral terminal sliding mode (ITSM) for the dynamic positioning (DP) of an unmanned marine vehicle (UMV) in the presence of model uncertainties and external disturbances. First, the implemented kinematic controllers in this study achieve local finite-time convergence of position errors to zero, while effectively circumventing the singularity problem typically encountered in conventional terminal sliding mode control (TSMC) approaches. Subsequently, a dynamic controller is designed for UMV by utilizing the output of the kinematic controller as the reference velocity command. An adaptive mechanism is devised to address the issue of unknown parameters in the upper bound of lumped uncertainty, which may involve thruster faults. Finally, based on above controllers, the finite-time stability of the entire closed-loop cascaded system is proved and the effectiveness of the proposed method has been demonstrated through comparative simulation results.