Cooperative Control Of Air-to-ground Robot

With the development of society,the technology of Unmanned Aerial Vehicle(UAV)and Unmanned Ground Vehicles(UGVs)play an important role in industries more and more.However,aiming at the increasingly complex operating environments and diverse tasks,the operation ability of a single UAV or a single UGV is extremely limited.Therefore,by cooperative control,they can take the place of workers who work in dangerous environments to perform D3 tasks(Dull,Dirty and or Dangerous missions,D3 missions),and they have a wide range of applications in both military and civilian fields.In this thesis,the cooperative control based on target guidance is researched in the application scenarios where air-ground robot is cooperatively tracking the escaped criminal in the forest,that is,a single target(UGV)guides a single UAV.The control objective is to design robust flight control system and cooperative control system for keeping the follower-UAV to track the leader-UGV at a relative distance.Firstly,the models of quadrotor UAV and UGV are modeled.Based on this,the controller with PD as position outer loop,linear active disturbance rejection control(ADRC)as attitude inner loop and the controller based on compensation PD are developed to control the position and attitude of the quadrotor UAV.A PID controller is designed to control the motor speed of the UGV.The developed method is simulated and the results show that the flight control method based on linear ADRC not only makes the flight control system stable,but also has strong disturbance rejecting ability,and the motor speed can reach the set value quickly.Secondly,a trajectory tracking controller is proposed based on Leader-Follower method to transmit the real-time position information of the ground robot to the quadrotor UAV control system for cooperative control.At the same time,aiming at the tracking error in the cooperative control process,the variable integral PID control is designed to optimize the two cooperative control methods to reduce the error.The proposed schemes are analyzed and the simulation results demonstrate that,with the cooperative tracking control method which is PD as position outer loop and linear ADRC as attitude inner loop,the UAV can track the trajectory of UGV fast.Finally,an experimental platform is set up to verify the effectiveness of the developed control methods.GPS data from the UGV and UAV are optimized by Kalman filter to improve positioning accuracy and the reference trajectory of the UGV is set,When the UGV moves in a straight line and an approximate rectangular trajectory,the UAV also tracks it in a variable flight speed,and at t =6.67 s and t =5.76 s,the maximum tracking errors are95.86 cm and 110.4cm respectively.The UAV can quickly track the UGV moving in a straight line with a tracking error of 0cm,while the tracking error is 40 cm and remains unchanged when the UGV moving in an approximate rectangular trajectory,and it shows that the UAV and the UGV keep a certain distance for tracking flight.The experimental data show that the relative distance between the UAV and the UGV changes when they start moving from static state at the same time,and then the tracking error is 0cm or 40 cm,which means the cooperative tracking control target is achieved and the requirements of application scenario are satisfied.