Path Planning And Communication Protocol Design In Multi-UAV Cooperative Coverage Task

In recent years,unmanned aerial vehicle(UAV)is becoming more and more widely used in military and civilian fields such as rescue,patrol,exploration etc.By reasonably planning coverage paths,UAV cluster can cooperate to achieve large-scale and complicated tasks,and collaborated UAVs can significantly improve the working efficiency at the basis of a high task completion rate.Hence,the path planning algorithm has a significant meaning for the efficient completion of actual tasks by UAVs.The current research on UAV coverage path planning problem mainly focuses on the path planning for single UAV,or is based on known environment.In contrast,the research on coverage path planning for multiple UAVs in unknown environment is insufficient.In addition,existing research assumes that UAVs can exchange the information among others ideally,and doesn’t consider the constraint of actual network communication.To address the path planning problem of multi-UAV joint coverage tasks,this thesis proposes a distributed multi-UAV coverage path dynamic planning algorithm,and further designs a network protocol among UAVs which can support the algorithm reliably.First,a multi-UAV coverage path planning algorithm is proposed for the multi-UAV cooperative coverage tasks.Inspired by the traditional single UAV Parallel Line Coverage and Spanning Tree Coverage algorithms,the Multi-UAV Parallel Line with Spanning Tree Coverage(MUPLSTC)algorithm in unknown environment is designed.To avoid repetitive coverage in the obstacle edge and in the boundary of the target area,a strategy of moving and swapping the edges of the spanning tree is proposed.It can significantly reduce the repetitive coverage rate of the path and the time consumption of task completion.To evaluate the execution efficiency of the algorithm in various circumstances reasonably,an obstacle region model is built.Based on the characteristics of UAV coverage task,five performance indicators including coverage rate,task completion time,average task time,energy consumption and repeat path rate are introduced to quantify the efficiency of the path planning algorithm.For the lack of that communication constraint among UAVs isn’t considered in most existing studies of coverage path planning,this thesis designs the application layer protocol based on MUPLSTC,namely Multi-UAV Coverage Task Application Protocol(MUCTAP),that can support multiple-UAV for real-time distributed path planning.By designing the sending and receiving logic and the format of the message exchanged,the protocol can properly operate under the situation where the communication quality is affected,and the information exchange among UAVs can be done,and the operation of dynamic path planning algorithm can be guaranteed.In addition,processing strategy of the protocol in case of failure of individual UAV nodes,including UAV failure detection,task re-planning for the normal UAVs,and cooperative coverage of UAV cluster when the failed UAV reconnects to the cluster.Last but not least,this thesis validates the validity of the proposed MUPLSTC algorithm and MUCTAP protocol by network simulation software OPNET.Simulation results show that for the multi-UAV cooperative coverage task in unknown environment,MUPLSTC proposed in this paper is suitable for various typical obstacle environments and can complete the path coverage task more efficiently.MUCTAP can guarantee the operation of dynamic path planning algorithm in the case of single UAV node failure,which improves the robustness of multi-UAV coverage tasks.