Velocity obstacle algorithms for collision prevention at sea

It is of critical importance to prevent collisions at sea for navigation safety. Some popular techniques have been proposed and been used in practice, e.g. closest point of approach, collision threat parameters area, etc. However, most of these techniques assume that the target ship keeps a constant velocity which is unrealistic and may easily lead to a false alarm. In this article, Velocity Obstacle (VO) algorithms are applied to support collision avoidance with target ships whose trajectories are non-linear (with time-dependent velocities) and (probabilistically) predictable. In particular, Linear-VO, Non-Linear VO, and Probabilistic VO algorithms are used for this purpose. Compared to traditional approaches, these algorithms are capable of detecting collision dangers with target ships sailing non-linearly and (probabilistically) predictably, finding collision-free velocities in multi-ship scenarios, and preventing collisions. Two scenarios are designed to demonstrate the performance of VO algorithms. The results show that the proposed VO algorithms can facilitate collision detection and offer proper collision-free solutions for ships.