Use of unmanned aerial vehicles for pesticide spraying on crops has expanded rapidly over the past 3 years, particularly in East Asia but in many other regions including North America. Regulatory agencies, crop protection companies and others have become increasingly aware of this expansion and the many open questions related to precision of application, air transport of spray material, and risk assessment. Multi-rotor UAV sprayers are unlike conventional aerial or tractor boom sprayers in many ways: payload and power constraints necessitating the use of ultra-low volume tank mixes, complex vortex effects, unusual nozzle configurations, different release heights, etc.  There is an emerging body of literature describing field testing of UAV sprayers in cropped plots with a focus on foliar coverage and product performance but far fewer studies that address questions of environmental and human safety. In particular, greater understanding is needed in the areas of in-swath uniformity and off-target spray drift under a variety of spraying conditions. Thus, a series of studies were initiated examining the effects of a range of spray settings, such as height, speed, spray quality and nozzle selection with the goal of understanding the factors that influence on-target and off-target deposition. A sufficiently robust body of data could help inform the development of a predictive modeling tool that can address the range of equipment and application scenarios that are foreseen with automated machinery.  This presentation describes the phase that was conducted in a wind tunnel in 2019. The wind tunnel was selected for certain variables that were believed to be too sensitive and/or difficult to control in a field setting, specifically the effect of payload and wind speed on spray pattern and downwind drift. Three different nozzle types were affixed in the under-rotor configuration to a DJI Agras MG-1P octacopter and sprayed with a fluorescent tracer in a wind tunnel, and the deposition collected from the near-upwind to a distance of 20 meters downwind from the center target. A key feature of this study design was a framework that allowed the drone to hover with minimal constraints so that it would adopt its attitude (pitch, roll, yaw) autonomously in response to the height requirement and wind perturbation, thus simulating the effects of a realistic field spray in the crosswind direction.

UAV spray testing in a wind tunnel

ACS Fall 2020 Virtual Meeting

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