Research On Ship Formation Algorithm Based On Leader-Follower Method

In recent years,in order to complete complex offshore work tasks and improve the efficiency of maritime transport,multi-ship collaborative work has gradually replaced single-ship work and been widely used in engineering.Ship formation plays an important role in maintaining the stability of multi-ship collaborative work.The difficulty lies in how to establish the formation structure effectively and keep the stability of the formation.At the same time,ship formation is inevitably affected by the external environment in the process of working at sea.When obstacles such as islands and reefs protruding from the water surface appear in the navigation environment,it is very important for ships to make collision avoidance decisions independently to ensure the safety of all ships during navigation.To solve the above problems,this paper proposes an algorithm based on the leaderfollower method of ship formation,combined with the path planning method of fast marching square method and the local collision avoidance method of virtual obstacle potential field method,which can effectively establish the formation structure and ensure the safety of all ships.The main research contents and achievements of this paper are as follows:(1)The global static path planning method based on fast marching square method is studied.Firstly,the basic principle and algorithm flow of fast marching square method are introduced.Secondly,the navigation environment is constructed into a 2D discrete space based on the characteristics of the fast marching square method,and the obstacle cells and passable areas are marked respectively.Then,the velocity potential diagram and arrival time map are obtained by iterating the generated map with the fast marching square method.Finally,based on the gradient descent method,a path is constructed on the entire arrival time map,which takes arrival time,smoothness and safety into consideration.(2)The formation control method based on leader-follower method is studied.Firstly,considering the communication relationship between the multi-ship formation system,the system can be constructed as a graph.Secondly,using the relative theory of graph theory,the relationship between nodes and edges in ship system diagram is described by Laplacian matrix.Then,based on the analysis of this relationship,the relative error distance between the follower and the leader is calculated,and the path tracking effect of the follower ship to the leader ship is realized by eliminating the error.Finally,a simulation environment is constructed in MATLAB,and the fast marching square method is combined with the formation control method based on the leaderfollower method.The experimental results show that this method can effectively provide a safe sailing track for the leader,and at the same time,the whole team can quickly form a preset formation and maintain the stability of the formation in the following voyage.(3)The local collision avoidance algorithm based on the virtual obstacle potential field method is studied.Firstly,the traditional artificial potential field method is analyzed and its defects are pointed out,that is,the unreachable target problem and the local minimum problem.Secondly,a virtual obstacle potential field method is proposed,which updates the potential field formula and solves the situation that ships may enter the local minimum point by adding virtual obstacles.Then,the virtual obstacle potential field method is combined with the leader-follower method.The combined method can effectively solve the unreachable target problem.Finally,the simulation experiment of the proposed algorithm is carried out in MATLAB.The experimental results show that when the ship encounters obstacles during navigation,it can timely conduct collision avoidance operations,and quickly return to the original team based on the leaderfollower method after leaving the collision risk.