Research On The Technologies Of Path Planning For USV Formation Based On Fast Marching Method

In recent years,with th e benefits of re ducing human casualties as well as increas ing mission efficiencies,there have been increasing deployments of USVs in both m ilitary and civilian applications.However,current available USV platforms have low payload capacity and short endurance times.In order to overcom e these shortcomings,the future trend of USV development is to dep loy multiple vehicles as a f ormation fleet to allow co operative operations.Path planning is the core com ponent of USV formation technology for global static path planning an d local dyn amic collision avoidance.Research on path planning of USV formation is of significant theoretical importance,and the applica tion value lies in the improvement of load capacity and mission diversity.Based on the leader-follower architecture a nd the fast m arching square m ethod,this paper complete global static path planning pr oblem and local dynam ic collision avoidance.Then this paper builds the m odel of USV and experiments it with the planned path in simulation.The contents of this research are summarized as follows:Firstly,this paper researches on global static path planning method.Global path planning includes the configuration space and the path s earching.The configuration space is the data structure corresponding to real environm ent and can be processed by com puter.The path searching is the algo rithm applied for confi guration space.Traditional configuration space merely divides real environment into two parts: free space and occupied space.The free space are thought to be isotropic,whic h means the whole free space is of same safety for the USV.This results that the planned pa th is often too close to obstacle.The fast m arching square method treats the free sp ace as anisotropic and assumes the safety is dire ctly proportional to the distance to obstacle.This results that the length of planned path is often too lar ge.This paper proposes the variable fast marching square m ethod to ch ange the anisotropy of free space to balance the safety and length of the pl anned path.The valid ity of the variable fast marching square method is verified by simulation experiments.Secondly,this paper researches on local dynamic collision avoidance.USV formation may encounter dynamic obstacle during operation.Traditional local path planning m ethod is based on sensor information and correct the global path,which has the problem of lar ge amount of calculation,less real-time performance and complex control structure.T his paper proposes the finite fast m arching square method and collision avoidance dom ain based on ship domain.The member of USV formation treats the other m embers as dynamic obstacle.The finite fast marching square method is used in the collision avoidance domain and adds the local safety map with global safety map.Then the final path is calculated.The validity of the finite fast marching square method is verified by simulation experiments.Thirdly,this paper models the USV and does simulation experiment.This paper assumes that identical USV are used in form ation.According to MMG m odeling methodology and taking disturbance force into c onsideration,this paper m odels the USV and solves it by the Runge-Kutta method.Based on MATLAB platform and PID control method,the simulation program for USV motion simulation is develope d,and the trajectory simulation results of USV under different conditions are obtained.