Reconfiguration Control For Unmanned Aerial Vehicles In Three-dimensional Space

Realization of reconfiguration control for UAVs is one of the most important research content in formation control field,in this paper,three-dimensional elastic formation control method is studied.The elastic formation control approach is a new method for formation controls,which is developed on the basis of leader-follower architecture.In the elastic formation control method,a desired look-ahead point is set up to describe the position that leader vehicle relative to the follower vehicle at the ideal moment of formation;the elastic look-ahead point is used to describe the dynamic position of leader vehicle that in the line of sight of follower vehicles.The elastic distance vector is applied to represent the changes in distance which wingman following leader vehicle.According to the relationship between the position of follower vehicle,elastic look-ahead point and leader vehicle,the formation control model is established.This paper put forward the mathematical description of three-dimensional elastic distance vector.The elastic distance vector is a linear function of flight velocity,and it can increase with the increase of flight speed,and vice versa,so the elastic distance vector has speed adaptability.On the basis of this,the control equation of formation is deduced by combining the second-order particle model of unmanned aerial vehicle.In addition,the control equation of whole formation is linear.The shape of UAV formation is formed by using desired vector about look-ahead point in the elastic formation control method.Based on the control equation of elastic formation,a formation keeping controller is designed in this paper.The formation keeping controller adopts position error information as feedback information,and the control law of each UAV is only related to the relative position information of two vehicles’ and the speed information of the locale vehicle.This controller can make the formation dynamically adjust the relative distance between leader and follower vehicles,with the changes of flight speed.Simulation results indicate that the controller can manage the formation adapt to the change of flight velocity.This has a positive significancefor safety of UAV formation flight.Meanwhile,the wingman can maneuver rapidly to track leader vehicle and maintain a desired formation.Consider a crucial task for formation reconfiguration is to provide a safe and feasible fight trajectory for each UAV.According to the requirement of flight mission,the problem of formation reconfiguration is described as a fuel or time optimal control problem.Consequently,this paper studies the optimal control algorithm of elastic formation reconfiguration.The Chebyshev pseudospectral method is used to transform the original optimal control problem into a nonlinear programming problem and then solve it.Finally,3-UAV formation reconfiguration is simulated using MATLAB combined with the tomlab toolbox.The results show that the optimal control algorithm can effectively complete the formation reconfiguration tasks.