Collision avoidance fault-tolerant control for dynamic positioning vessels under thruster faults

This paper explores a collision avoidance fault-tolerant control scheme for dynamic positioning vessels in the presence of velocity constraints and thruster faults. First, the collision avoidance problem for multiple static obstacles is described as security zone constraint and integrated into the controller design via an artificial potential function. Second, an indirect error vector including the gradient of potential function and vessel velocity information is constructed, and a time-varying asymmetric barrier Lyapunov function is adopted to concurrently guarantee the satisfaction of velocity constraints. With the help of robust adaptive techniques, the derived controller not only provides robustness against unknown parameters affections, ocean disturbances, and thruster faults, but also has a simple structure and inexpensive online computations for real-time implementation. Finally, the asymptotic convergence of the gradient of potential function and vessel velocity is demonstrated, while a positioning control task for a dynamic positioning vessel is presented to evaluate the effectiveness of the proposed method.