Collision risk identification of autonomous ships based on the synergy ship domain

In this paper, a novel ship domain model termed synergy ship domain (SSD) is proposed. Unlike other ship domains, the proposed SSD is more useful and more flexible to identify the dynamic changes of collision risk. In this paper, the safety passing ship domain is integrated with the early warning ship domain and based on the synergetic theory, the SSD model is constructed so that the collision risk of two vessels under the same encounter situation are the same. Meanwhile, according to the navigation characteristics of autonomous ships, this paper constructs the theoretical framework of dynamic identification of collision risk, and defines two kinds of collision risk thresholds for closed-quarters situation and immediate danger situation. The thresholds can be dynamically changed according to different waters and different needs. This identification framework of collision risk is more adaptable to autonomous ships, compared to other conventional frameworks, it to some extent can meet the requirements of intelligent identification of collision risk. Finally, several computer simulations have been conducted which are based on three encounter situations to identify the dynamic changes of collision risks. Simulation results demonstrate that the proposed SSD is more effectively and more directly to identify the collision risk, and also demonstrate that the real-time collision risk identification based on the SSD are reasonable and dependable.