Research On Uav Trajectory Planning With System Design And Implementation

In recent years,with the advancement of communication,materials,control and other technologies,the Unmanned Aerial Vehicle(UAV)industry has also achieved a rapid development.The UAV has been widely used in the military and civilian fields due to its small size,strong maneuverability,and high concealment.As an important support for UAV applications,trajectory planning technology has become a research hotspot at home and abroad.However,the current trajectory planning methods still have problems such as low safety and can not deal well with dynamic obstacles in the environment.This paper studies the quadrotor UAV trajectory planning technology,improves the existing methods for its problems,and designs a UAV trajectory planning system.The contributions are summarized as follows:(1)A global trajectory planning method for high safety is studied.In this paper,a two-stage global trajectory planning method is adopted.In the front-end path search part,the traditional A* search algorithm is improved with the ESDF map,which increases the distance between the path and obstacles by adding a safety cost item to the cost function.At the same time,a topologically equivalent waypoints extraction algorithm is proposed,which can reduce the number of waypoints while maintaining the safety of the path.In the back-end trajectory generation part,this thesis uses a piecewise polynomial curve to represent the trajectory to meet the smoothness of the trajectory,and proposes an environment-adaptive time allocation scheme,so that the speed of the UAV is positively related to the safety of the environment,thereby further improving the safety of the trajectory.Finally,the effectiveness of the method is proved by simulation experiments.(2)The local trajectory replanning method in dynamic environment is studied.First,the point cloud of obstacles is clustered using the DBSCAN clustering algorithm,and the clustering results of adjacent frames are matched to obtain the position sequence of different obstacles in consecutive frames,then the least squares method is used for velocity estimation.Then,this thesis proposes an efficient collision detection method in the spatio-temporal domain to determine the trigger time of replanning.In the part of trajectory optimization,this thesis uses the quasi-uniform B-spline curve to represent the trajectory,and combines the velocity information of obstacles to propose a trajectory optimization method in the spatio-temporal domain.Finally,the simulation and comparison experiments prove that the method proposed in this paper can effectively improve the autonomous obstacle avoidance ability of UAVs in environments with dynamic obstacles.(3)A UAV trajectory planning system is designed and implemented.In this paper,the software part of UAV trajectory planning is constructed based on the Robot Operating System(ROS),and the UAV hardware platform is built by using depth camera,onboard computer,and other equipment.The effectiveness of the system is verified by a real aircraft flight experiment in an outdoor environment,and it is also validated that the trajectory planning method proposed in this paper can be applied to the real environment.