| In recent years,rotary-wing unmanned aerial vehicles(UAVs)have been widely used in military and civilian applications due to their portability,flexibility and low cost.However,the limited endurance has become a bottleneck in various applications of rotary-wing UAVs:on one hand,the lightweight and flexible characteristics make a rotary-wing UAV unable to carry too much energy;on the other hand,compared with fixed-wing UAVs,a rotary-wing UAV needs to overcome the gravity directly through their own rotors,which leads to the higher energy consumption.Being restricted by the current level of the industrial technology,it is difficult to improve the endurance of a rotary-wing UAV.Therefore,the current research focus is how to optimize the flight energy consumption by improving the use of the rotarywing UAV in the application to enhance its endurance.The goal is to increase the flight distance of the rotary-wing UAV after one charge,so as to enhance its task execution ability in a practical application.The main tasks of rotary-wing UAVs in many applications are to travel the specific points in the task areas.The travel path is the key to determine the flight mode of a rotary-wing UAV.Therefore,it is a main way to optimize the energy consumption of a rotary-wing UAV through planning its flight path in an application.The current research on path planning for a rotary-wing UAV is mostly focuses on getting the shortest path,so as to achieve the optimization of related indicators including energy consumption.However,the actual flight experiments prove that the rotary-wing UAV's energy consumption is not only related to the flight distance,but also to the turning situation in the flight,and the turning along a polygonal line or along an arc will have different effects on the energy consumption.For this reason,in the research on the path planning method for the optimization of rotary-wing UAV's energy consumption,the distance of the path is not only considered,but also other path features are introduced,such as the turning angle(i.e.the included angle between the old flying direction and the new flying direction),the arc radius and the arc length.The main contents and innovation of this dissertation are as follows:(1)An energy consumption estimation model based on turning angles and distance is proposed,which can be used to estimate the energy consumption of a rotary-wing UAV flying a polygonal line path.Based on this model,the features of an arc path,such as arc radius and arc length,are introduced as the parameters of energy consumption estimation.Then an energy consumption estimation model of arc path is also proposed,which can be used to estimate the energy consumption of a rotary-wing UAV flying an arc path.The two models can be used to solve the inaccurate estimation caused by only using the distance feature to measure energy consumption.The actual experiment results show that the energy consumption predicted by the proposed energy consumption models is close to the actual energy consumption,and the established models are effective.It is also found that i)the bigger the turning angle is,the higher the energy consumed by turning is;ii)when a large turning angle is divided into several small turning angles to realize the turning,the energy consumed by the turning will be reduced;iii)an arc,as the limit case of dividing a turning angle,is the better shape of a flight path with the same turning angle.These findings and the proposed energy consumption estimation models provide the foundation for the research on path planning methods for the energy consumption optimization.(2)A path planning method for optimizing rotary-wing UAV's energy consumption based on the fusion of turning angles and distance is proposed.By using the energy consumption estimation model based on turning angles and distance in(1),the path planning for optimizing rotary-wing UAV's energy consumption is modeled as a 0-1 integer linear programming problem and a three-dimensional weight matrix is constructed.Then a path planning algorithm based on the greedy strategy is put up to solve the problem.The simulation and experiment results show that i)the path planned by this method has lower energy consumption than that one planned by the method which only uses distance to estimate energy consumption and plan a path based on the greedy strategy;ii)the influence of turning angles on rotary-wing UAV's energy consumption can not be neglected.(3)A path planning method for optimizing rotary-wing UAV's energy consumption based on arc features is proposed.By using the two energy consumption estimation models in(1),the path planning for optimizing rotary-wing UAV's energy consumption is modeled as a mixed integer non-linear programming problem.Then a mechanism of curving a polygonal line path is given,and combining with the path planning strategy proposed in(2),a two-stage path planning algorithm is presented to solve the problem.The simulation and experiment results show that i)compared with the method in(2)and the method only using distance to estimate energy consumption and plan a path based on the greedy strategy,this method can find a path having much lower energy consumption;ii)the energy consumption can be effectively reduced by dividing a large turning angle into several small turning angles(the limit case is an arc),that is,an appropriate curve path is more energy-saving than a polygonal line one.(4)A path planning method considering charging and optimizing rotary-wing UAV's energy consumption is proposed.For a large-scale task area or massive tasks,sometimes a rotary-wing UAV can't complete all tasks even if it is fully charged.To solve this problem,charging piles are required in the task area in this dissertation.However,how to optimize integratedly the positions and the number of charging piles and the flight energy consumption of the rotary-wing UAV becomes a new challenge.To address this challenge,the path planning combining the deployment of charging piles with the energy consumption optimization of a rotary-wing UAV is modeled as a 0-1 integer linear programming problem.A failure prediction mechanism is provided.Based on the greedy strategy and the proposed mechanism,a predictive path planning algorithm is designed to solve the problem.While the optimal path is obtained,the number and the positions of the charging piles to be deployed are also determined.The simulation results show that this method can find a suboptimal energy-saving path and a small number of positions that need to deploy charging piles are determined.Moreover,compared with the method using multiple rotary-wing UAVs cooperation and combining the greedy strategy,and the method using a single rotarywing UAV to return to the service station for charging and combining the greedy strategy,this method is the best,because the path planned by this method has lower energy consumption and shorter distance. |
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