The effect of UAV sprayer operational characteristics on spray deposition within the target area

In recent years, unmanned aerial vehicles (UAVs) have emerged as a promising technology in agriculture. In aerial spraying, accurately estimating droplet distribution is crucial for evaluating the effectiveness of the spraying process. This study presents the application of spectroscopy and a machine vision-based droplet detection system to develop tools for testing and evaluating UAV sprayers under static and field conditions, demonstrated through the assessment of a specific UAV sprayer. A droplet detection system was designed and developed, consisting of a frame, drive and driven rollers, a stepper motor, LED lights, a power supply, a camera, and Mylar sheet. This system was used in both static and field evaluations. The results showed that the spray width for a single nozzle of the UAV sprayer was approximately 2.5 m. To achieve the lowest coefficient of variation, the optimal distance between adjacent flight paths was determined to be 2.6 m. Both the volume median diameter (VMD) and number median diameter (NMD) increased with distance from the nozzle. Average of deposition ranged from 0.00 to 0.096 μL/cm², with the highest deposition occurring along the centerline of the flight path and decreasing with increasing distance from the centerline. Lowering the altitude significantly reduced wind drift. Due to the influence of wind, turbulence generated by UAV rotor rotation, and downwash airflow during the field test, the VMD and NMD values were lower than those observed in the static test.