# Development and Prospect of UAV-Based Aerial Electrostatic Spray Technology in China
## 3 Rapid Progress of UAV-Based Electrostatic Spray Technology
### Continuous Optimization of UAV-Based Electrostatic Spray Technology
Therefore, aerial electrostatic spray could significantly improve droplet deposition and prevent drift. In terms of the mechanism of influencing factors, [PERSON] [38] designed an electrostatic spray system based on the FR-200 large-load unmanned helicopter with a maximum load of 80 kg. The charge and spray characteristics of the electrostatic spray system were studied, and the prediction models of the charge to mass ratio and droplet size were established. The characteristics of deposition and drift of electrostatic spray of heavy load unmanned helicopter were analyzed by field experiments. It was concluded that the charge voltage, flight height, and crosswind wind speed were the main factors affecting the drift and deposition of an electrostatic spray of FR-200. The results showed that the charge voltage had the greatest influence, followed by the crosswind wind speed, and the flight height had the least influence. Based on the research results, the mathematical model was established between the center distance of droplet mass and droplet drift rate and the charged voltage, flight height, and crosswind wind speed. [PERSON] et al. [39] introduced response surface analysis (RSM) into the optimization design of spray parameters of Electrostatic spray system of UAVs. A response surface model with injection pressure and nozzle diameter as design variables and droplet charge to mass ratio as optimization objectives was constructed. The performance tests of the new electrostatic spray system under different nozzle diameters, spray pressures, and electrostatic voltages were carried out. It showed that the nozzle met the theoretical requirements of optimal biological particle  
Figure 4: Electrostatics physical model of aerial electrostatic spraying based on charge transfer space loop [36]. Figure 3: UAV paddy field spraying operations [35]. size and the requirements of hydraulic spray control for most crop diseases and insect pests. The validity of the model was also proved. In addition, multivariate analysis of variance showed that nozzle diameter, spray pressure, and electrostatic voltage have important effects on performance. The influence of the two factors on the deposition density and uniformity is the spray pressure, the nozzle diameter, and the optimal combination of the factor levels to obtain the best results. Chinese scholars also carried out research on multiple operating parameters and their interaction effects on the performance of aerial electrostatic spray systems. [PERSON] et al. [40] simulated the spray performance of UAV-based electrostatic spray systems at different flight heights by measuring the droplet diameter under different nozzle apertures and system pressures and obtained the optimal flight parameter combination. [PERSON] et al. [41] studied the spray deposition with three factors: spraying duration, charging voltage, and flight height. The experimental results showed that the back-front ratio of droplets on the back and front of leaf targets could reach 158.8% under indoor conditions, and the droplet size on the back was smaller than that on the front. The number of droplets increased with the accumulation of spraying time without affecting the back-front ratio. Higher charging voltage and lower spraying height for the aerial electrostatic spray system can achieve a better deposition effect and higher back-front ratio. [PERSON] et al. [42] established theoretical equations of droplet group charge based on the water inductive charging theory and then studied the effects of electrode figuration (electrode ring diameter, electrode spacing, spray pressure, and charge voltage) on droplet charging and spray performance through experiments. Under the action of an electrostatic field, the droplet size decreased obviously with the increase in charged voltage. The charge performance improved with the decrease in electrode ring diameter. [PERSON] et al.