A Study Of Automatic Collision Avoidance Of Ships Based On Dynamic Hierarchical Potential Field Method

How to improve the automation level of ship collision avoidance and reduce the influence of human factors in the collision avoidance process has been a concern of the navigation community.In this paper,the potential field method is used to model the ships' navigational environment,and its application in the automatic collision avoidance of ships is studied.When the conventional potential field method is applied to the dynamic obstacles avoidance planning,it is prone to situations in which the agent cannot circumvent the obstacle or unreasonable avoidance.The dynamic potential field is built by introducing the repulsive potential function of velocity.The simulation results show that the dynamic potential field method can overcome the above defects of the conventional potential field method.The models of Ship collision risk index(CRI)are established by fuzzy inference and fuzzy comprehensive evaluation,respectively.By comparing and analyzing,the fuzzy comprehensive evaluation model is selected and applied to quantify CRI.According to the International Regulations for Preventing Collisions at Sea(COLREGS)and its related research,the avoidance actions of own ship under different encounter situations were determined,and the repulsive potential function of velocity was adjusted accordingly.The collision avoidance process of own ship is divided into three stages:track keeping,avoidance,and track restoration.According to the requirements of different stages,the dynamic hierarchical potential field is built.Dynamic hierarchical potential field method is used to model the ships' navigational environment,and then the appropriate heading command is generated,on this basis,the automatic collision avoidance system is built,the autopilot is used to generate the rudder angle command to control the ship to complete the avoidance,track restoration,and track keeping.The simulation experiments demonstrate that the automatic collision avoidance system in this paper can guide the ship to complete the determined avoidance actions;it can guide the ship to pass the target ship at a safe distance of approach as well as guide the ship to avoid multiple target ships;it has the adaptability to changing navigational environment,and has track keeping ability.