An Effective Ship Control Strategy for Collision-Free Maneuver Toward a Dock

Ship maneuvering toward a dock is a hot research topic in the field of autonomous ships. How to realize autonomous low-speed maneuver to a designated location under environmental disturbances is the fundamental problem at present. In addition, potential collisions with other nearby vessels and evasive maneuvers that meet maritime regulations increase the complexity of maneuvering. This paper presents an effective ship control strategy for collision-free maneuver toward a dock. In the strategy, a line-of-sight (LOS) algorithm is utilized to steer the ship along a pre-planned path toward the dock. A collision risk factor that takes ship's maneuvering characteristics, ship domain and relative velocity into account is designed for collision avoidance. Evasive maneuvers complying with the main rules of the international collision avoidance regulations at sea can be achieved based on the risk factor. A ship bumper is constructed, based on which the strategy can switch to either “path following” or “collision avoidance”. Numerical simulations for different encounter situations including head-on, starboard-crossing and overtaking under wind perturbations are carried out. The results show the proposed strategy is able to keep the ship domain free during maneuvering and steer the ship to the docking area in a safe and appropriate manner.