Research On Trajectory Control Of Formation Flight And Reconfiguration For Multiple Unmanned Aerial Vehicles

Compared with a single Unmanned Aerial Vehicle(UAV),formation flight has advantages in system redundancy,robustness,and task diversification.Hence it attracts more and more attention nowadays.During the UAVs formation flight,formation reconfiguration is often inevitable when the tasks or the environment changed.In this process,real-time path planning and accurate path following are necessary.Focused on the issues of the real-time path planning and accurate path following,some works are carried out in this paper.The main contents are as follow:Firstly,the control method and modeling approach of multi-UAVs are discussed.For the study of path following,a three degree-of-freedom point-mass model is built to describe the dynamics of a single UAV.Based on the analysis of different formation flight control strategies and modes for UAVs,the concrete strategy is chosen according to the difference in fly stages.The model of leader-follower is built,which is essential for the following research.Secondly,to guarantee the flight stability and accuracy of path following for UAVs,the control method based on real-time transition trajectory generation is put forward.In this section,the existence condition,computation method and conversion rules of transition trajectory are discussed at first.Then the reasonable range of guidance length of Nonlinear Guidance Law is derived with detailed analysis.To correct the track error when the UAV deviates from the expected position,an adaptive guidance length algorithm is proposed.Then an evaluation criterion combining the rapidity and overshoot is put forward accordingly.At last the effectiveness of the proposed method is verified by the numerical simulations.Next,the real-time path planning problem in 2-dimensional plane for the reconfiguration of UAVs formation is researched in the paper.To satisfy the real-time requirement,a strategy combining online path re-planning and speed adjustment is adopted.After that,a high dimensional mathematic model of path planning for the reconfiguration of multi-UAVs formation is built.A dimensionality reduction process is carried out based on the Dubins Trajectory.With the simplified model,the Particle Swarm Optimization(PSO)algorithm is adopted to search the optimal transform trajectory.At last,a simulation of formation reconfiguration from horizontal formation to vertical formation is presented,to verify the rapidity and effectiveness of the path planning method.Finally,to confirm the research results in the paper,a simulation on the actual observation mission of UAVs formation flight is presented.The basic flight mission introduction,variable selection,parameter determination,simulation process and data analysis are performed.The simulation results show that the proposed path planning and path following methods in the paper are effective to the formation reconfiguration and trajectory control,and beneficial to the mulit-UAVs formation flight.