Aiming at the obstacle avoidance problem of the plant protection unmanned aerial vehicle（ UAV）

a kind of obstacle avoidance system based on millimeter wave radar is designed. The system consistes of millimeter wave radar

arithmetic processing module and flight control module. A cooperative detection scheme of dual millimeter wave radars is proposed to adapt to the posture change of the plant protection UAV. Based on the characteristics that echo center of millimeter wave radar changes within the size range of the obstacle

the width of the obstacle is detected. By reducing the fluctuation of transverse distance

the stability of obstacle lateral distance detection is improved. Corresponding obstacle avoidance around flight parameters are detected according to the obstacle detection parameters. Experimental result shows that this obstacle avoidance system can detect obstacle parameters effectively. The detection error of front distance is less than ± 115 mm

the detection error of side distance is less than ± 195 mm

the detection error of width is less than ± 235 mm

the lateral movement error and forward movement error are less than ± 500 mm

it can accurately complete obstacle avoidance flight of the plant protection UAV.