Collision Avoidance Decision System For Inland Ships Based On Velocity Obstacle Algorithms

With the continuous growth of China's economy,the continuous prosperity of logistics and freight transportation and the gradual deepening of North-South trade,inland shipping has increasingly become an irreplaceable important mode of transportation,which plays a vital role in regional economic integration and cargo trade liberalization.However,in the increasingly high-intensity and high-density transportation environment of inland rivers,the problem of ship safety is becoming more and more serious..For a long time,ship collision is the most serious factor affecting ship navigation safety and causing accidents.This problem is not only reflected in the wide sea area,but also more significant in the inland river environment with narrow and long waterways.The collision accident of ships in inland rivers not only caused huge economic losses,but also directly threatened the life safety of crew members.Due to the complex environment of inland river waters,the traditional collision avoidance algorithm applied to wide sea areas is difficult to meet the practical needs.Aiming at this problem,this paper proposes an inland river collision avoidance decision model based on improved velocity obstacle algorithm(VO),which aims to assist ships to meet the inland river collision avoidance rules and realize independent collision avoidance operation under the condition of ship maneuverability;At the same time,the algorithm has certain reliability,real-time and stability to ensure that effective collision avoidance instructions can be obtained in different situations.The main work of this paper is as follows:(1)This paper summarizes the relevant knowledge of inland river environment and inland ship collision avoidance in China.Combined with the inland river collision avoidance rules,this paper analyzes the basic collision avoidance operations of ships in inland rivers,expounds the avoidance principles of ships when sailing in inland rivers,and defines the collision avoidance responsibilities of ships in different encounter situations.(2)Establish the mathematical model of inland ships,including the design of ship domain model,ship motion model and ship collision risk model.Among them,the mathematical model analyzes the force of ships in inland rivers,and improves the traditional ship motion model applied to wide sea area — MMG model to a ship motion model suitable for inland river environment.(3)The situation that ships need to adopt collision avoidance behavior in inland river environment is analyzed,and the speed obstacle method,which is widely used in agent,is introduced to provide the corresponding collision avoidance decision.On this basis,aiming at the inland river environment,this paper improves the speed obstacle method,and puts forward an improved speed obstacle method based on the field of eccentric elliptical ships.The improvement of velocity obstacle algorithm includes:first,the obstacle classification model is established.Second,the safety distance is considered and the speed buffer is set up.Third,the speed obstacle area is divided again.These improvements are convenient to deal with different collision avoidance situations.Finally,potential threats are also considered to achieve collision avoidance in an urgent situation.(4)The auxiliary decision-making experimental environment for collision avoidance of inland ships is built by MATLAB software.The collision avoidance of ships against static obstacles(shoals,reefs,etc.)and dynamic obstacles(under the head-on,crossing,and overtaking situations)in inland rivers is simulated.At the same time,the collision avoidance of multi ship complex encounter situation and urgent situation is tested.By analyzing the simulation results,it is confirmed that the improved speed obstacle method is feasible and effective to solve the collision problem of inland ships,and can provide reasonable collision avoidance decision for inland ships.