Energy-efficient Path Planning Of Unmanned Surface Vehicle Considering Marine Environment

With the development of human society,the total amount of marine economy is constantly high,and the production activities of countries in the world in marine space are also very active.Therefore,the reasonable development and protection of the ocean has become an important premise to ensure the sustainable development of marine economy.As an important equipment for marine development and protection,USV plays an important role in civil and military,and has a broad development prospect.However,the problem of insufficient endurance of USV in operation has become one of the important factors restricting its development and application.Therefore,it is of great significance to reduce the energy consumption and improve the endurance of the USV.Therefore,this paper puts forward a method to improve the endurance of the USV by improving the navigation path of the USV in the marine environment.By adjusting the course of the USV and making rational use of the sea wind,wave and current load in the marine environment,the purpose of saving energy is achievedFirstly,the main environmental factors that affect the energy consumption of the USV during navigation are determined,and their effects on the USV are described mathematically.In order to ensure the accuracy of the energy consumption function,the mathematical model of the resistance of the USV under the action of sea wind,wave and current is established,and then it is introduced into the dynamic model of the USV.Considering that the environmental load of the USV is different when the heading is different,the mathematical model of the energy consumption of the USV is defined as the superposition of the energy consumption per unit distance.Secondly,the environment modeling method is determined.In this paper,the grid method is selected to model the simulation environment.In the process of building the environment model,the relationship between the size of the grid unit and the size of the USV should be considered in the expansion of the obstacle grid to avoid collision;In addition,each grid not only contains its own binary marine environment information,but also has its own angle of corresponding position.When the course of the USV changes,the angle of its neighborhood should also change accordingly,so as to accurately evaluate the energy consumption.Then,the appropriate path planning algorithm is selected and the algorithm is improved according to the marine environmental impact.Through the analysis and comparison of various common path planning algorithms,this paper selects the classic A* algorithm for the shortest path planning,and uses the established energy consumption model to improve the A*algorithm,and obtains a path planning method based on optimal energy consumption(Energy-A*,referred to as EA*).Then,the programs of the two methods are written in C++language,and the simulation results of the two methods are compared and analyzed by selecting five groups of different levels of marine load strength,seven groups of different angles of environmental load direction and five different sizes of speed.The results show that compared with EA * algorithm,although the total range of the path obtained by A* algorithm is shorter,its energy consumption is higher.The energy consumption and path will be changed when any one of the influencing factors changes in the intensity,direction and speed of the environmental load,and other influencing factors remain unchanged.In addition,the redundant steering problem in the simulation results is optimized.The simulation results under the selected environmental load and speed show that the total range error rate of the optimized A* algorithm is reduced to 0.311 %,and the energy saving rate of the EA* algorithm is increased from 30.4 % to 54.3 %,which further improves the reliability of the method.Finally,the energy consumption of EA * algorithm and the reason of path change are analyzed and discussed in different environment load and different speed simulation.When the direction of environmental load is different,the node with less environmental force will be selected preferentially under the condition of constraining the total voyage.Therefore,the closer the direction of load is to the vector direction from the start to the end,the closer the direction of USV is to the direction of load,the shorter the total voyage,the greater the thrust and the lower the total energy consumption.When the environmental load intensity is different,with the increase of the intensity,the amplitude increases gradually,resulting in a sharp increase in energy consumption,and the energy consumption caused by steering is minimized when planning the path.The faster the speed is,the greater the hydrostatic resistance is.But with the increase of load intensity,the faster the speed is,the shorter the lateral load resistance time is,and the smaller the total energy consumption is.