# Development and Prospect of UAV-Based Aerial Electrostatic Spray Technology in China
## 3 Rapid Progress of UAV-Based Electrostatic Spray Technology
### Summary  
To sum up, a large number of field experiments have been conducted in China to test the actual performance of the electrostatic spray system based on UAVs. For the convenience of comparative analysis, Table 1 summarizes the researches on UAV-based electrostatic spray systems. From the perspective of the test scheme, the system pressure, flight height and speed, charging voltage, rotor wind speed, and their effects on each other were studied. Chinese scholars have also completed a lot of work using theoretical simulations of the spray system, the improvement of the electrostatic nozzle, and the optimization of the aerial chemicals. In terms of the mode of charge, most studies adopt the induction mode of charge with the highest safety. The inductive charging voltage is usually between 2 kV and 15 kV, and the electrode making and insulation methods are easy to be realized, which is the most developed method of charging droplets at present [47]. In addition, contact charging has also been tried in China, which has also achieved good results [34; 35; 36; 41; 45]. However, it needs to keep the absolute insulation of the spray system in the charging process, which puts forward high requirements for the design method and safety.  
Figure 6 illustrates the key achievements of the aerial electrostatic spray technology and the research groups over a timeline. Since 2015, China's UAV-based aerial electrostatic spray technology has developed rapidly. In general, although the UAV-based electrostatic spray technology is a new technology, it is gradually being improved. Compared with the electrostatic spray system on manned aircraft, plant protection UAVs have more development prospects in China at present. With the operation area covered exceeding 67 million \(\mathrm{hm}^{2}\), the plant protection UAV has developed from an early experimental product into a common agricultural production machine in China [48]. It is of great practical significance to study the fusion and influence mechanism of UAV and aerial electrostatic spray systems, which contributes to the field of agricultural aviation plant protection in the future.  
Figure 5: HY-B-15L single-rotor plant protection unmanned helicopter for cotton defoliant spray (a) and TXA616 plant protection UAV for rice growth regulator spray (b) [46].  
\begin{table}
\begin{tabular}{c c c} \hline HY-815, single rotor & & & & & & \\ plant protection & & & & & \\ taxi micro & & & & \\ taxi micro & & & & &  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Test Device** & **Charged Mode** & **Test Target** & **Test Method** & **Evaluating Indicator** & **Test Environment** & **Researchers and Affiliation** \\ \hline response surface & & & Nozzle diameter, nozzle & Droplet deposition & & & \\ methodology (RSM) & Induction & - & pressure, and electrostatic voltage & characteristics and & Simulation & [PERSON] et al., Guizhou University \\ \hline \multirow{3}{*}{Gade Adv.5 plant protection UAV} & \multirow{3}{*}{Contact} & \multirow{3}{*}{Mock target} & Comparison of & & & \\  & & & electrostatic spray and & characteristics & Outdoor & [PERSON] et al., Shandong University of Technology \\ \cline{3-6}  & & & non-electrostatic spray & & & \\ \cline{3-6}  & & & & & & \\ \cline{3-6}  & & & & & & \\ \cline{3-6}  & & & & & & \\ \cline{3-6}  & & & & & & \\ \cline{3-6}  & & & & & & \\ \hline \end{tabular}
\end{table}
Table 1: _Cont._