Research On UAV Obstacle Avoidance Based On Improved VFH Algorithm

With the rapid iteration of quadrotor UAV autonomous flight technology,quadrotor UAV gradually with small size,lightweight structure,flight maneuverability,endurance and other technical advantages,widely used in urban attractions and publicity,jungle,alpine exploration and other complex obstacles in the environment to perform tasks.To improve the obstacle avoidance flight performance of quadrotor UAVs in complex obstacle environments,and to solve the problems of tortuous paths,detection lags and dead loops caused by oversized obstacles when avoiding obstacles have become hot research topics in the industry.To address the above technical challenges,this paper takes a certain type of quadrotor as the research object,designs and builds an UAV obstacle avoidance hardware platform by carrying out research on an improved vector field histogram based obstacle avoidance algorithm,and completes the verification of the UAV obstacle avoidance process demonstration flight.The research content are as follows:(1)The flight mechanism of the quadrotor UAV is analyzed,and a quadrotor UAV flight dynamics model is established with reference to the knowledge of nonlinear six degrees of freedom to design a quadrotor UAV simulation model.In order to make the established model reflect the characteristics of the UAV,a series-level PID control algorithm is adopted to realize the design of attitude hold control and trajectory tracking controller,and experimental numerical simulation is conducted.The simulation results show that the designed controller can make the UAV achieve stable flight and position tracking,which greatly ensures the stability of the attitude and position signal of the quadrotor UAV.(2)The research is carried out for the technical problems such as path curvature,detection lag,and dead loop caused by too large obstacles when quadrotor UAVs fly autonomously to avoid obstacles.First,for the UAV path curvature,detection lag,and the threshold-sensitive defects of the traditional VFH algorithm,the relevant adaptive threshold function is proposed,and the threshold is dynamically adjusted according to the constraints such as the distance and speed between the UAV and the obstacle,and an improved vector field histogram algorithm obstacle avoidance strategy is constructed.Secondly,the problem of local dead loops is caused by the large size of obstacles and the inability of UAVs to detect all information about obstacles.By designing an improved cost function to identify in advance the landmark states that fall into dead loops,the algorithm autonomously adjusts the priority of UAV flight direction selection online,thus ensuring that the UAV avoids obstacles effectively.(3)Carry out the hardware design of the four-rotor UAV obstacle avoidance system and the implementation of the embedded flight control and obstacle avoidance algorithm,complete the minimum system design of the flight controller hardware,the selection of obstacle avoidance sensors,the customization of data communication protocols and the improved VFH obstacle avoidance algorithm Realization,to provide a demonstration flight platform for verifying the correctness of the algorithm design in this paper.(4)The four-rotor UAV obstacle avoidance and control system is tested for flight subjects,including attitude maintaining mode,fixed height mode,and autonomous obstacle avoidance flight mode test.The test data is analyzed,and the results show that the four-rotor UAV can effectively avoid obstacles in the target route.