| Formation control is one of the research hotspots of multi-UAV system.The state convergence time and convergence error of control are two major indexes to evaluate the formation control of multi UAV.Many domestic and foreign research results on this work are relatively mature.However,how to control the formation of multiple UAVs in close formation is still a key problem to be solved.This work is also of great significance.In some special occasions,such as rescue and relief,reconnaissance and detection,attack and defense and other complex occasions,sometimes a single UAV is difficult to deal with or solve,and the formation space of multiple UAVs is too narrow,so it is necessary to minimize the distance between UAVs and consider the impact on each other caused by each other.In this paper,the formation control of multi UAV system in close formation is studied.The research work of this paper is mainly divided into the following aspects:First of all,the influence of vortex on the wingtip of UAV formation is analyzed.It can be seen from the analysis and theoretical derivation that the wingtip vortex is subjected to an additional up wash speed and an additional side wash speed.For multi UAV formation with close formation,the additional up wash speed will change the lift and resistance of the wingman,and the additional side wash speed will change the lateral force of the wingman.Through the analysis of its mathematical model,it can be concluded that the optimal formation configuration of multi UAV system under the condition of close formation is that the longitudinal spacing is twice of the span,the transverse spacing is ?4 of the span,and the height difference is zero.Under this condition,the lift of the wingman is the largest,the resistance is the smallest,and the lateral force is negligible.Then,the traditional PID controller is designed to control the multi UAV close formation,and the simulation verification is carried out for the UAV formation control under the influence of aerodynamic coupling and aerodynamic coupling,stable and disturbed conditions.Through the comparison of simulation results,it can be seen that the existence of aerodynamic coupling effect makes the formation control of multiple UAVs more complex,which will increase the convergence time and steady-state convergence error.Secondly,on the basis of completing the formation control of the traditional PIDcontroller for the multi UAV system under the condition of tight formation,an improved PID formation control method based on the fuzzy control principle and the basic pigeon group optimization algorithm is proposed.Firstly,based on the UAV close formation system,the corresponding fuzzy variables are selected and the corresponding fuzzy control rules are formulated,and then the UAV close formation control framework based on the fuzzy control principle is constructed.Then,the pigeon group optimization algorithm is used to optimize the PID control parameters,and the corresponding fitness function which can express the accuracy of formation is selected.Finally,aiming at the problem of long convergence time of state curve and large error of stable state when using PID controller to control formation,a formation control method based on improved pigeon group algorithm and improved artificial potential field method is proposed.This method uses the improved artificial potential field method instead of PID controller to find the ideal next time state of UAV formation;through the partial update rules of quantum particle swarm optimization algorithm combined with pigeon swarm algorithm to increase the optimization performance of the algorithm,the designed optimization algorithm is used to iteratively optimize the fitness function representing the UAV formation degree,.The simulation results show that the algorithm is suitable for the formation control of multi UAV system under the condition of close formation,and its control effect is much better than that of using PID controller to control close formation of multi UAV system. |
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