Design Of UAV Formation And Obstacal Avoidance Control System Based On Virtual Leader

Compared with single unmanned aerial vehicle,multi-unmanned aerial vehicle formation has the characteristics of high efficiency and cooperative ability to complete complex tasks in search and other tasks,so it has great research value.One of the difficulties of UAV swarm control is how to switch the formation of UAV formation safely and how to avoid collision as a whole.Therefore,for the formation control of UAV formation,a virtual navigator control method combining artificial potential field is proposed in this thesis,which realizes the safe exchange of aircraft formation from plane formation to three-dimensional formation.In the case of obstacles in the environment,aiming at the problem of obstacle avoidance and collision avoidance among internal elements in the process of obstacle avoidance,this thesis adopts the method of combining the global reference trajectory based on raider map and local programming to get the preliminary trajectory,and obtains the smooth target trajectory through spline curve,so as to achieve the overall safety obstacle avoidance of the fleet.The thesis uses PX4 open source flight control system and Gazebo physical simulation software to verify the effectiveness of the proposed algorithm.The main work of this thesis is as follows:1.In order to realize the safe switch of UAV formation,a formation control method of virtual navigator based on artificial potential field is proposed in this thesis.The distributed second-order consistent control method based on virtual navigator is adopted to realize the function of multi-unmanned aerial vehicle system forming in a certain formation,and the function of all unmanned aerial vehicles in the system tracking the virtual navigator in a formation formation.In order to solve the problem of collision between unmanned aerial vehicles(UAVs)in the formation process and the formation change process,a smooth truncated artificial potential field method is adopted to avoid collision within the cluster.In addition,the Hungarian algorithm is used to realize the task allocation in formation switching process,which ensures the shortest total distance in formation switching process.2.In order to solve the obstacle avoidance problem of UAV formation in three-dimensional complex scenes,this thesis combines the global reference trajectory and the strategy based on local occupancy rasters map,and proposes an online path planning method for multi-UAV system to realize the obstacle avoidance in formation.By constructing the global reference trajectory between the starting point and the final target point,the point on the global reference trajectory is taken as the local target point,and then the local spline curve trajectory is constructed.The local occupancy razer map and A* path search algorithm are used to realize the function of UAV group obstacle avoidance.On this basis,an improved particle swarm optimization algorithm is proposed to solve the optimization problem with spline curve control points as independent variables and the distance between the trajectory and obstacles as constraints.The balance between the smoothness of the trajectory and the success rate of planning is realized.3.The thesis uses PX4 open source flight control system,Gazebo physical simulation software,and related modules of ROS system to build a simulation experiment platform.In the simulation environment,taking hexagonal and octahedral formation switching as an example,the formation switching from plane formation to three-dimensional formation is realized,and the formation control algorithm is verified.Taking the complex scene of multiple aircraft passing through multiple obstacles as an example,the effectiveness of the swarm obstacle avoidance algorithm is verified.