Research On Multi-UAVs Cooperative Trajectory Planning And Control Method

Unmanned Aerial Vehicle(UAV)has attracted more and more attention in the military and civil fields as its characteristics which include strong maneuverability,low cost and effective response to the harsh environment.However,with the promotion of information technology and intelligent technology,the future complex application environment puts forward higher requirements on the UAV's rapid response capability,control performance and cooperative degree etc.They will become the key problems for UAV which are taking full advantage of multi-UAVs cooperative task performance and improving the UAV's control system robustness to suppress the influence of the internal uncertainty and external disturbance.Based on the above background,the research goal of this paper is obtaining the UAV trajectory planning result with high efficiency and precision,and achieving no-error trajectory tracking with the influence of the internal uncertainty and external disturbance.In this paper,the trajectory planning algorithm for single UAV,the cooperative trajectory planning for multi-UAVs,and the inner-loop altitude steady controller and outer-loop position tracking controller for the quadrotor UAV through the theory of nonlinear system control are presented to provide the foundation on the engineering application for UAV autonomous control in the complex environment.In this paper,the trajectory planning problem in complex environment for single UAV is studied firstly.By introducing the concept of additional control force,the combination algorithm based on the artificial potential field method and the optimal control problem direct method is proposed.The algorithm uses artificial potential field force to describe the shape and size of the obstacles for reducing the number of the constraints greatly and decreasing the solving difficulty for the optimal control problem.Through the single obstacle and complex-obstacle environment simulations,the algorithm can effectively deal with trajectory planning problem in the complex obstacle environment.The results retain the advantage of the artificial potential field method to simplify path planning model,and inherit global optimality from the optimal control algorithm when solving the trajectory planning problem.In order to solve the strong constraints problem in trajectory planning,the novel optimization variables of multi-UAVs are introduced.Aiming at the problem of flight collision and the demand of the cooperative target in multi-UAVs cooperative flight process,this paper proposes a novel time collaborative planning algorithm based on the time constraint set.By this algorithm,flight collision avoidance problem and cooperative combat issue are integrated and transformed to an optimization problem with unequal signal.Then,the optimization problem is transformed to a standard parameter optimization by the introduction of integer linear programming,and the optimization algorithm is utilized to solve the problem.Through the simulations,the time collaborative planning algorithm can ensure the flight collision avoidance and meet the collaborative combat requirements by one-time optimization,and the algorithm has high computational efficiency and widely applied value.In solving the problem of multi-UAVs cooperative trajectory planning,this paper creatively divides the complex problem into the outer-loop time collaborative planning problem and the inner-loop trajectory planning problem.Among them,the inner-loop trajectory planning problem utilizes the real quadrotor UAV model directly as the optimization object and proposes the reference attitude angle variables as the optimization variables.The inner-loop controller can be introduced to meet the requirements of flight stability.The outer-loop time collaborative results set the launch time constraints as a basis and calculate the UAVs'departure time by the time collaborative planning algorithm.Though the organic combination of the two outer-loop planning and inner-loop planning problems,multi-UAVs cooperative trajectory planning problem can be effectively dealt with in the complex conditions.For multi-UAV trajectory planning results,this paper designs the tracking controller based on nonlinear system control theory for the dynamic model of quadrotor UAV.The controller consists of outer-loop position tracking controller and the inner-loop attitude stabilization controller.The inner-loop attitude stabilization controller uses robust H_?optimal control theory,and designs the state feedback controller by seeking the Lyapunov function.The outer-loop position tracking controller utilizes the nonlinear model predictive control theory to realize the high performance of the no-error tracking control.Through the comparison simulation with the traditional PID controller,the LQR controller and the backstepping controller for the quadrotor UAV in the ideal condition,the rotational inertia uncertain condition and the external force disturbance condition,the control method presented in this paper is verified to be more robust.