Finite-time Formation Control For Multi-quadrotors Systems

With the development of rotorcraft technology,single unmanned aerial vehicle(UAV)is widely used in various fields,such as investigation,disaster relief,power inspection and logistics.However,there are some limitations on the size,sight and load for one UAV.Once it is attacked or damaged,it will cause the mission to fail.The cooperative operation of multiple UAVs can make up for these problems,which has better fault tolerance,expansibility and robustness.It also can improve the efficiency of execution when performing complex tasks.Based on the finite-time consensus theory and event-triggered communication mechanism,this paper designs a distributed formation control algorithm for multiple UAVs,and builds an experimental platform to verify the algorithm.The main contents of this paper are as follows:Firstly,a hierarchical formation control framework is proposed for multiple UAVs system,which includes upper coordinating control layer and lower tracking control layer.In the upper control layer,the coordinating control algorithm is designed based on finite-time consensus theory to get the virtual speed and position such that the virtual speed reach the consensus,and the virtual position reach the desired virtual formation shape.In the lower layer,the tracking control algorithm is designed based on PID theory,which makes the real position and speed track the virtual position and speed respectively,and finally the desired formation shape of multiple UAVs forms.The stability of the control algorithm is further analyzed,and the simulation results verify the feasibility of the hierarchical control framework.Secondly,the event-triggered communication was introduced into the coordinating control layer based on the hierarchical control framework.The event-triggered communication mechanism is mainly designed by trigger condition.The UAV will communicate and update control inputs only when it reaches the trigger condition.Therefore,the algorithm combined event-triggered communication mechanism with finite-time consensus can effectively reduce the numbers of communication between multiple UAVs and saves energy.At the same time,the stability analysis and simulation results of the controller were list.Finally,we built an indoor multiple UAVs system experimental platform and three UAVs.Each UAV was equipped with an onboard processor with ROS robot operating system,raspberry pi 3b,in addition to Pixhawk flight control,which can realize the information of neighboring UAVs in the local area network.The indoor positioning system use Opti Track motion capture,which can provide a unified ground coordinate system.In the real experiment,three UAVs and a ground vehicle were used as the followers and leader respectively.The UAVs can form their own formation and keep unchanged while tracking the ground vehicle.