Collision-avoidance path planning for multi-ship encounters considering ship manoeuvrability and COLREGs

Ship collision prevention has always been a hot topic of research for navigation safety. Recently, autonomous ships have gained much attention as a means of solving collision problems by machine control with a collision-avoidance algorithm. An important question is how to determine optimal path planning for autonomous ships. This paper proposes a path-planning method of collision avoidance for multi-ship encounters that is easy to realize for autonomous ships. The ship course-control system uses fuzzy adaptive proportion-integral-derivative (PID) control to achieve real-time control of the system. The automatic course-altering process of the ship is predicted by combining the ship-motion model and PID controller. According to the COLREGs, ships should take different actions in different encounter situations. Therefore, a scene-identification model is established to identify these situations. To avoid all the TSs, the applicable course-altering range of the OS is obtained by using the improved velocity obstacle model. The optimal path of collision avoidance can be determined from an applicable course-altering range combined with a scene-identification model. Then, the path planning of collision avoidance is realized in the multi-ship environment, and the simulation results show a good effect. The method conforms to navigation practice and provides an effective method for the study of collision avoidance.