Research On Ship Collision Avoidance Path Planning Under The Situation Of Multi-ship Encounter

Smart ship is a hot spot in the current shipping-related research field,and the realization of ship autonomous navigation is an important goal of intelligent ship research and development,and the realization of this function should first focus on solving the problem of ship autonomous collision avoidance planning.In the research of autonomous collision avoidance planning under the situation of multi-ship encounter,the constraints of the International Regulation for Preventing Collision at Sea(COLREGs)and the factors such as possible uncoordinated actions among target ships that should be considered,are the difficulty of ship autonomous collision avoidance.This thesis focuses on those problems.First of all,this thesis comprehensively considered the heading,speed,relative orientation and other factors of several ships that will encounter,and uses the ship collision risk model to calculate the collision risk index of the ships that will encounter at present.According to the collision risk index of the incoming ship,the problem of multi-ship collision avoidance planning is divided into the general multi-ship collision avoidance planning problem,which is encountered by multiple target ships and own ship,but does not constitute the collision risk at the same time.And the special multi-ship collision avoidance planning problem in which several(more than one)target ships and this ship pose the risk of collision at the same time.Then,according to the types of multi-ship collision avoidance planning problems and the requirements of the COLREGs,this thesis obtained the constraints that different multi-ship collision avoidance planning problems should be meet.Finally,this thesis established the ship domain model,improved the velocity obstacle algorithm,and designed a ship collision avoidance planning algorithm suitable for different multi-ship encounter situations.Based on the velocity obstacle algorithm combined with the ship domain model and the COLREGs for different multi-ship collision avoidance problems.Among them,for the improvement of the velocity obstacle algorithm,the work of this thesis is as follows: in order to be compatible with the ship domain model,a new collision detection method is designed;in order to solve the disadvantage that the traditional velocity obstacle algorithm can not feedback the global information,the rolling window algorithm is introduced to improve it,and the path cost and yaw quantity are taken into account in the obstacle avoidance action to avoid the occurrence of large angle steering.In addition,in order to give the avoidance path and obtain the heading speed curve which is convenient to guide navigation,the cubic B-spline method is introduced to smooth the heading speed value in the unit window.In order to verify the feasibility of the collision avoidance planning system designed in this thesis,the multi-ship encounter in two different encounter scenarios is simulated at the end of the thesis.The simulation results show that the multi-ship collision avoidance path planning algorithm proposed in this thesis can ensure that the actions taken by the experimental ships can not only comprehensively consider the impact on the ship caused by the possible actions between ships in the current navigation environment,but also follow the requirements of the rules.Safe to avoid all surrounding ships.