The Influence of Lateral Wind Velocity on Spray Drift Dynamics of Liquid Droplets Sprayed by Agricultural Robot

During the spraying operation, it is important to consider the environmental conditions, particularly the wind velocity. Droplets carried by the wind out of the spray zone may be carried onto nearby plants, soil, water bodies, residential areas, etc. Various measures have been developed and used to reduce droplet drift to address this problem. Robotic spraying systems, such as unmanned aerial vehicles and spraying robots, are now increasingly being used. The influence of lateral winds on the spraying processes of these systems has not yet been extensively investigated. In this study, spray coverage and spray drift of manufactured artificial plants were investigated. Spraying was carried out with an XAG R150 spraying robot and a lateral wind from 2 m s−1 to 8 m s−1 was generated with an air flow generation stand by varying the air flow velocity every 2 m s−1. Spray coverage on the artificial plants was measured at two heights (0.5 and 1 m). The droplet coverage measurements were significantly influenced by the lateral wind velocity and the height of the plant coverage measurement site. The results showed that even in the presence of a high lateral wind velocity (v = 6–8 m s−1), the droplet spray had better coverage of the middle part of the artificial plant (0.5 m from the ground) than the upper part (1 m from the ground). For the spray drift studies, three solutions with low concentrations (0.1%) of chemical drift reduction agents (DRAs) were sprayed, with water as control. It was found that the proportion of drifting droplets also increased with increasing lateral wind velocity. The spray coverage at 3 m from the spray zone (spray drift) was 1.6% at a lateral wind velocity of v = 2 m s−1, 4.2% at v = 4 m s−1, 5.3% at v = 6 m s−1, and 8.1% at v = 8 m s−1. The use of DRAs was able to reduce spray drift in strong (v = 8 m s−1) lateral winds. It was found that at 3 m from the spray zone, at a spray height of 1 m, the spray coverage was about 40.7% lower than that of water for DRA1, 44.4% for DRA2, and 43.2% for DRA3.