| Quadrotor UAV has the advantages of vertical take-off,landing capability and fixed-point hovering.Further,multi-quadrotor cooperation can effectively overcome the defects of low efficiency,poor fault tolerance and single function of single machine.Formation tracking control of quadrotors is a typical application of multi-aircraft cooperative control,considering the uncertain factors such as interference and obstacles in the environment,quadrotors can form and maintain the desired formation and track the desired reference trajectory so as to complete the predetermined task.This paper study the control of single quadrotor,multi-quadrotor formation tracking control and obstacle avoidance of quadrotor under external disturbance.The main work is as follows:(1)Analyze the realization process of the linear motion and angular motion of the quadrotor,and establish a single-quadrotor dynamics model with uncertain terms.Aiming at the problems of sliding mode surface chattering and the inability to achieve finite time convergence of the traditional sliding mode control,Super-Twisting and terminal sliding mode are combined to design a new continuous terminal sliding mode controller(CNSTM).At the same time,taking wind disturbance as an example,this paper considers the influence of external disturbance on the control of the quadrotor,and uses the expanded state observer combined with the above-mentioned sliding mode control to realize the position and attitude control of the quadrotor under disturbance.(2)Establish a graph theory model of the quadrotor formation,design a formation tracking control protocol including position and speed information to realize the variable formation tracking control,and obtain the stability condition and robustness of formation consistency.(3)Consider obstacles in the actual flight environment and the collision of UAVs by neighboring UAVs,a three-dimensional artificial potential field method based on an improved reinforcement learning method is proposed.Aiming at the obstacle avoidance and collision avoidance problems of the quadrotors in the formation,this paper introduces the obstacle repulsion field and the inter-aircraft repulsion field to take into account the unsafe factors in the flight environment.At the same time,in order to solve the local minimum problem inherent in the artificial potential field,SARSA is used to predict the location where the UAV may fall into the local minimum in advance and avoid it to ensure the safety of the formation and the continuous tracking of the target.(4)Design a formation containing 5 quadrotors,and the system can accomplish the formation path planning and autonomous navigation flight successfully.The effectiveness of the above system is verified through simulation experiments. |
