With the wide application of UAVs,its defects and shortcomings are gradually exposed,and UAV formation technology emerges as the times require.Compared with a single UAV,a formation composed of multiple UAVs can complete more complex and changeable tasks.Therefore,the research direction of scholars from various countries has gradually shifted to the formation control technology composed of multiple UAVs.This paper takes the quadrotor UAV as the research object,and discusses the three issues of UAV formation,including formation maintenance,trajectory tracking and cooperative obstacle avoidance.The specific research is as follows:Firstly,establish the basic model of UAV dynamics and kinematics,analyze and study the UAV formation flight problem under the master-slave structure according to its mathematical model,and decompose it into two parts: that is,the formation of the formation and the slave aircraft.The maintenance problem and the trajectory tracking problem of the host are briefly introduced.Then,the stability theory of the Lyapunov function and the traditional artificial potential field method theory used in the subsequent formation obstacle avoidance are briefly introduced,so as to make sufficient preparations for the following research.Secondly,in view of the formation maintenance problem,according to the relative kinematics model of the master and the slave in the master-slave mode of the formation,the relative position channel of each UAV in the horizontal and vertical directions and its vertical direction during the flight process of the formation are studied and analyzed.There is no coupling relationship between the relative position channels of.Therefore,the PID control method is used to design the vertical channel of the UAV,while the horizontal and vertical channels of the UAV are designed by the backstep method.The desired linear and angular velocities required to follow the host and maintain the formation are obtained.So far,the problem of maintaining control of the formation of the slave aircraft during the formation flight has been completed.Then,for the trajectory tracking problem of the host,the kinematics model of the host divides it into altitude control channels,yaw control channels,pitch control channels and roll control channels with feedback properties.For each channel control system,a control method combining integral method and backstepping method is used to design it.The controller designed by each channel is combined to form the trajectory tracking controller of the main engine,which solves the command problem that the main engine can follow the desired trajectory under interference during the formation flight.Combining the slave formation maintaining controller with the host trajectory tracking controller,a formation flight controller is constructed and simulated.The final result verifies the effectiveness of the formation flight strategy.Finally,it is studied whether the multi-UAV formation can complete the overall obstacle avoidance of the formation in the complex obstacle space,and at the same time ensure that there is no collision between the UAVs in the formation and maintain the stability of the formation.Aiming at the obstacle avoidance problem of a single UAV,it is proposed to add a dynamic adjustment coefficient factor to the traditional gravitational and repulsive force functions.While optimizing the action range and change form of the traditional force field,it also solves the problem of trajectory jitter when the UAV avoids obstacles.The integral disturbance component is added and the longitudinal random factor is added to solve the local minima problem.For multi-UAV formation cooperative obstacle avoidance,the improved artificial potential field method combined with the distributed consistency theory is proposed to design the formation cooperative obstacle avoidance.Inside the formation,by designing the mutual virtual force between the drones,the formation can avoid collision and maintain a stable formation under the action of the virtual force between the drones;outside the formation,an improved artificial potential field method is used to enable the formation to Avoid obstacles.Finally,the formation can achieve the effect of internal and external cooperative obstacle avoidance under the action of the virtual force between machines and the external potential force. |