Tracking control of ship at sea based on MPC with virtual ship bunch under Frenet frame

This note focuses on the waypoints-based path following control of underactuated surface vehicles (USV) with the mechanism of static or slow time-varying obstacles avoidance at sea. In order to track curved path while avoiding obstacles, a virtual ship bunch (VSB) method is proposed based on Frenet frame with route optimization and motion limitations. To serve the need of VSB, path curve is parameterized via event triggered online fitting. Through model predictive control (MPC), the planned motion is tracked and optimized under constraints, while stability is guaranteed by Lyapunov theorem. Compared with existing researches, the VSB-MPC scheme has good robustness to model perturbation, the smoothness of manipulation is guaranteed by explicit planning under Frenet frame. Comparative experiments have been presented to demonstrate the merits of the proposed scheme.