Abstract
The aerial spraying of pesticides by plant protection unmanned aerial vehicles (UAV) is a process in which the spray droplet deposition on target sites occurs under the influence of the downwash wind field. The downwash wind field is the most important factor affecting droplet deposition distribution characteristics in an aerial spray. To understand the mechanism of the downwash wind field, spray tests were conducted at different flight heights by using a DJI UAV, and the downwash wind field in the three-dimensional direction (X-directional wind, Y-crosswind, and Z-vertical wind) was measured by using a wind speed measurement system for UAV. Combined with the droplet deposition of aerial spray, the distribution characteristics of the downwash wind field and the influence of the downwash wind field on droplet deposition were studied. The results showed that it had obvious differences in the distribution of the downwash wind field for UAV at different flight heights. As the flight height increases, the downwash wind field in X-direction and Z-direction showed a strong to weak trend, while the downwash wind field in Y-direction showed an opposite trend. In addition, it was found that the downwash wind field in Y-direction and Z-direction both have a significant influence on droplet deposition. With the increase of flight height, the change of the downwash wind field led to a gradual decrease in droplet deposition in the effective spray area, and droplets deposited more uniformly. For the DJI T16 plant protection UAV in this test, the optimal flight height was 2.0 m, and the downwash wind field had a better improvement effect on droplet deposition. Therefore, in order to make full use of the downwash wind field of UAV, the appropriate flight height should be selected to improve droplet deposition of liquid pesticide and achieve a better control effect for crop disease and pests when UAV is used for aerial spray operations in the field. This study revealed the influence mechanism of the downwash wind field on droplet deposition of aerial spray, and proposed appropriate operation parameters from the perspective of practical operation. It was expected to provide data support for improving the operation quality of aerial spraying and the formulation of field operation specifications.
Highlights
Chemical application is an important agricultural production method of controlling plant diseases, insect pests, and weeds
Due to its high spraying efficiency, better atomization effect, and pesticide utilization, and solving the problem that ground machinery is difficult to use in the field during crop growth, plant protection unmanned aerial vehicles (UAV) is gradually becoming the preferred method of plant protection operations [7,8,9]
The main downwash wind field in Y-direction was concentrated below the fuselage, and it was mainly distributed at the lower right of the fuselage with the peak wind speed of 4.2 m/s
Summary
Chemical application is an important agricultural production method of controlling plant diseases, insect pests, and weeds. In the current crop production process, traditional manual and semi-mechanical operations are still the main methods of plant protection in China, which have low efficiency and high labor intensity, and cause low utilization of pesticides [3,4]. Due to its high spraying efficiency, better atomization effect, and pesticide utilization, and solving the problem that ground machinery is difficult to use in the field during crop growth, plant protection UAV is gradually becoming the preferred method of plant protection operations [7,8,9]. The use of plant protection UAV to spray pesticides for the prevention and control of crop disease and pests has become a new feature in the development of plant protection machinery
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