Motion Planning Method For Unmanned Surface Vessels Based On RRT Algorithm

With the development of sensor technology,communication technology,and computer technology,unmanned surface Vessels(USVs)capable of autonomously performing navigation tasks have received increasing attention.Motion planning is one of the important basic technologies for achieving the autonomy of USVs,which is developed from path planning and trajectory planning.Its main task is to plan a track that can be tracked by USVs or directly provide motion control instructions to USVs based on the specific navigation task while considering the motion characteristics of USVs.Currently,the general idea to solve the motion planning problem of USVs is to first perform path planning and then smooth the results of path planning to obtain a track that can be tracked.However,this method may generate new collision risks because collision detection is generally not considered in the smoothing process.Route recalibration is one of the common problems encountered when USVs are executing navigation tasks.At present,the route recalibration method is generally to abandon the original planning results,format the entire algorithm and task space,and then perform planning and calculation,resulting in low recalibration efficiency.Therefore,this paper proposes a motion planning method that considers the motion constraints of USVs and an efficient route recalibration method based on the Rapidly Exploring Random Tree(RRT)algorithm,including the following two aspects:(1)A motion planning method for USVs based on the RRT algorithm is proposed.This method is based on the motion constraint model of USVs,and optimizes the node connection of the RRT algorithm,while using collision detection rules to perform realtime calculations.Therefore,the method can effectively improve the trackability of the planning results and avoid the risk of collision.To verify the feasibility and advancedness of the method,feasibility experiments and comparative experiments are set up.The feasibility is verified by using different task spaces as environmental variables,and the degree of node optimization and the number of collisions generated by the motion planning results are used as quantitative indicators to compare this method with other motion planning methods,clarifying its advantages in application.(2)A route recalibration method for USVs based on the RRT algorithm is proposed.This method is based on the idea of random tree segmentation,using newly added obstacles to segment the random tree into residual random trees,and then using the residual random tree as the basis to grow and generate recalibration results.Finally,the feasibility of the method is verified by setting up feasibility experiments,and further comparative experiments and variable influence experiments are set up to analyze the calculation convergence speed of the method and its influencing factors.The RRT algorithm-based motion planning method for USVs takes into account the motion characteristics of the vessel and fully considers collision avoidance during planning,resulting in a 100% node optimization rate and zero possibility of collision.This advanced method has a certain applicability.The RRT algorithm-based route replanning method for USVs can avoid newly added obstacles during re-planning calculations while making reasonable use of the original planning results.It has a faster convergence speed compared to other algorithms,with an average speed-up of over 30%.