Adaptive Velocity Obstacle Avoidance for Multi-Vessel Encounters

Numerous methodologies based on velocity obstacles have been developed for marine collision avoidance over the past decade. They are typically limited to one or two ship encounters, sequential ship encounters and/or lack safety guarantees in scenarios involving multiple obstacles. This paper proposes an adaptive collision avoidance strategy based on the velocity obstacle method to safely avoid multiple dynamic obstacles (one, two or more) simultaneously while navigating towards the waypoint in partial compliance with the Convention on International Regulations (COLREGs) rules. Our avoidance strategy is based on the construction of the adaptive velocity cone according to the motion of the dynamic obstacles that ensures safety with the obstacles at all times. We implement the proposed avoidance strategy on a set of standardised scenarios, namely, Imazu problems for multi-vessel encounter situations. We compare our proposed strategy with the standard velocity obstacle method for multiple dynamic obstacles and found that our approach is better than standard in terms of minimum safety distance between the ship and the obstacles.