| Unmanned aerial vehicle(UAV)is widely used in military and civil fields,such as patrol reconnaissance,search and rescue,emergency communication support and so on.UAV formation control is of great significance for multi UAV cooperative missions,which enables UAV cluster to complete more complex tasks without collision,and greatly improves the success rate of tasks,avoiding the risks of single UAV failure.At present,the research on UAV formation control mainly focuses on the small-scale UAV cluster control,while there is less research on large-scale UAV cluster control.In addition,when UAVs are performing missions,the quality of networking between UAVs,as well as the requirements of formation keeping and transformation are not taken into consideration while studying formation control methods.Therefore,this paper studied the requirements of formation maintaining and communication networking in formation control of fixed-wing UAVs and proposed a distributed hierarchical formation control algorithm of UAVs.The UAVs were divided into three layers,where different control algorithms were used for each layer to accomplish the control and formation keeping of the entire formation.Considering the formation requirement of UAV formation,in this control algorithm,the formation could keep stable or changed according to the mission requirement.Also the control algorithm had good adaptability when UAV was large scale.At the same time,aiming at the problem of large number of broadcast messages in UAV AD hoc network,a routing protocol based on OLSR was designed to reduce the overhead of broadcast messages in the network through MPR forwarding mechanism and number forwarding mechanism.In the meantime,according to the stability of the current formation,the protocol could adaptively adjust the message sending frequency,so that on the basis of adapting to high-speed dynamic network,the protocol could reduce the overhead of controlling message as much as possible.Finally,this paper validated the formation algorithm of UAV in formation simulation software.The simulation results showed that the control algorithm could maintain and transform the formation according to the task requirements during the formation movement of UAV,and the applicability of the control algorithm in the scene with obstacles as well as the scene of UAV fault was verified.Through the joint simulation with the communication simulation software,it was verified that the proposed UAV AD hoc network routing protocol was fully applicable to the hierarchical formation control algorithm,and could effectively reduce the communication overhead and improve the quality of network communication. |
