Stereoscopic test method for low-altitude and low-volume spraying deposition and drift distribution of plant protection UAV

Abstract: With the widespread application of plant protection unmanned aircraft vehicle (UAV) in China, the application technology of plant protection UAV has attracted attention, and the environmental risk from the uniformity of deposition distribution and droplet drift loss is also an important question. At present, there are few test methods focusing on the droplet distribution in the environment of plant protection UAV. In this paper, a set of stereoscopic test methods for low-altitude low-volume plant protection UAV was designed mainly based on the international standards ISO 22866 and ISO 24253. The methods concluded two parts of the ground distribution and airborne distribution. The ground distribution was collected by the standard collectors (Petri dishes and Polyvinyl Chloride card) arranged on the ground according to the ISO standard. The airborne distribution mainly used a vertical sedimentation testing framework. The droplets of aerial drift were collected by Polytetrafluoroethylene lines and rotary tube brushes. The accurate flight parameters (fight speed and working width) of each test were captured by a camera UAV (Phantom 4A, produced by DJI) above the ground 80 m. Two three-axis ultrasonic anemometers (Gill, USA) were installed above ground 2 and 5 m respectively, which could obtain real-time meteorological data including the wind speed, wind direction and temperature. There were four types plant protection UAVs for testing, the MG-1s (DJI, 8 rotors), 3WQF-120-12 (Anyang Quanfeng, 1 rotor), 3W-TTA6-10 (Beifang Tiantu, 6 rotors) and 3W-TTA8-20 (Beifang Tiantu, 8 rotors), they were tested respectively with the nozzles of IDK 120-015 and TR 80-0067 produced by Lechler (Germany). A new calculation method was proposed, and total deposition around UAV was calculated for verifing the accuracy of method. Total ground sedimentation and aerial disappearance were calculated to represent all available pesticide, and evaluate the environmental risk respectively. The results showed that the ground deposition rate of all tests was between 53.6% to 76.6%, the highest ground drift rate was rich to 17.4%, and the airborne drift rate could be as high as 14.7%. This test system could collect 62.4%～101.7% droplets around the UAV sprayed by plant protection UAV. The drifts of 4 tested plant protection UAV installed IDK nozzles were obviously less than that with TR nozzles, meanwhile, the nozzle changing also reduced the ground deposition in some tests. Different plant protection UAVs had different distribution regular patterns of deposition when they installed TR or IDK nozzles. It meant the designs of different plant protection UAVs needed to select the right nozzles after finishing the distribution test for different types of nozzles. Thus, the most suitable nozzle type of each UAV should be tested and selected before the UAV working. This test method can effectively and systematically collect and analyze the droplets distribution of plant protection UAV and the drift regularity in the work area, which can provide a new reference for the comprehensive evaluation of the plant protection UAV.