Airflow characteristics of rotorcraft plant protection UAV operating in rice fields

Rotorcraft unmanned aerial vehicles (UAVs) cause movement of the rice crop which is an important indicator of the effectiveness of spray applications. A method of acquiring im-ages of the effects of airflow on the spray target by video aerial photography and computer vision to process the images was examined to obtain the characteristic information in rice fields; the dimensions of the disturbed area of crop, the so-called "rice vortex". Orthogonal experiments were designed to investigate the three factors of take-off mass, flying height and flight speed of the plant protection to assess the four indices of trailing distance, trailing stability, area and shape of the rice vortex. The results show that the influence of the three factors on the vortex trailing distance and its stability was in the order of flight speed, flight altitude and take-off mass. The effects on the vortex area and vortex shape were speed > mass > height. Analysis and discussion of the characteristics and morpho-logical features of the airflow targets revealed that the greater the distance and longer the duration of the trailing vortex, the more easily the rice vortex was disturbed and dissipated, and the lower its stability. Changes in the shape of the rice vortex mainly occur in its length, and changes in width are smaller. The results provide a data collection method and basis for further development of flight parameter-airflow target-application effect models. The four parameters of the trailing distance, stability, vortex area, and vortex shape constitute technical parameters suitable for assessing the effects of rotorcraft plant pro-tection UAVs operating in rice fields.(c) 2023 IAgrE. Published by Elsevier Ltd. All rights reserved.