In order to solve the multi-objective collision avoidance problem of unmanned surface vehicles (USVs) in open waters, this paper takes a medium-sized USV as the object and carries out the research and application exploration of a local path planning algorithm based on the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS).

A virtual obstacle line method is proposed to load the constraints of COLREGS based on the RRT algorithm for meeting the practical requirements of collision avoidance path planning in open water. In light of the problem that the RRT algorithm does not consider the speed dimension, a velocity obstacle (VO) algorithm is introduced. Next, a VO-RRT fusion algorithm is proposed and given the most dangerous obstacle strategy in order to solve the problem of real-time collision avoidance under multi-objective conditions.

The simulation and real ship test results show that the proposed algorithm has better real-time performance and takes less than 50 ms to undertake path re-planning. The collision avoidance path planned by the algorithm meets the relevant requirements of Articles 6, 8 and 13–18 of COLREGS. The proposed method can effectively deal with the multi-target collision avoidance problem in open waters.

The proposed method has good rule compliance, real-time and safety performance, and high practical value.