旋翼无人机气流特征及大田施药作业研究进展

旋翼植保无人机近年发展迅速，已出现大量施药作业的相关研究成果。针对目前研究现状中基础作业体系不清晰、关键问题研究不深入的问题，该文聚焦旋翼无人机施药目的，明确指出旋翼气流的存在是旋翼植保无人机大田作业的典型特征。围绕该特征，提出旋翼无人机大田施药作业基础体系，依照农药装载搬运-农药转化雾滴-雾滴空间运动-雾滴植株扩散-施药作业方法的主线，分别对旋翼无人机的机体、药箱、雾滴物理状态、运动状态、旋翼气流、对靶沉积、脱靶飘移、气流与作物互作、雾滴附着、机体控制、喷施量控制及作业模式等基本要素的研究现状进行归纳总结，梳理旋翼无人机施药作业体系的内在逻辑关系，探寻施药作业体系中待深入研究的基础科学问题。指出目前旋翼无人机大田作业亟需解决作业体系内容研究不均衡、机理研究不深入的问题；亟需解决作业参数关联性不强、大田试验条件精准性有待提高的问题；亟需解决作业模式无法直接表征作业效果、高精度飞行参数难转化为作业参数的问题，并给出深入研究的相关建议。期待广大学者提高对旋翼气流相关研究的关注度，围绕旋翼无人机大田作业体系中的实践与技术难点，寻找出具有旋翼气流特征的物理参数，提炼基础科学问题，加强工程应用研究。

Research progress on airflow characteristics and field pesticide application system of rotary-wing UAV

Abstract: As an important platform in precision agricultural aerial application, automatic chemical and pollination applications using rotary-wing unmanned aerial vehicle (RW-UAV) in real field conditions draw more attention among researchers, and become a hot research topic in crop protection. Many researches have focused on the pesticide application systems, operational parameters and operational modes based on the RW-UAVs, which contributed to the vehicle design, key technologies in the pesticide application and the accessory technologies. However, problems still exist due to a lack of in-depth understanding of the operational system and key issues in the pesticide applications based on RW-UAV. With the rapid development of RW-UAV technology in recent years, there have been more interests and studies conducted in the aerial pesticide applications using the RW-UAV platforms, especially in some Asian and European countries with small and fragmented agricultural fields. Most of the current researches in this area lack a clear and in-depth understanding of the fundamental characteristics and principles of the airflow during operation, which are the key parameters and trait in pesticide application based on RW-UAV. According to the major processes of the pesticide application protocol based on RW-UAV including loading and carrying of chemical, chemical turning into droplets, movement of droplets in the air, droplets deposition on plant canopies,, we summarized the research in terms of RW-UAV platform, chemical tank, droplet physical state, movement state, rotor airflow, deposition on targets, off-target drift, airflow and crop interaction, droplet attachment, UAV platform control, spray control and operation mode. Current pesticide application based on RW-UAV has issues in the lack of thorough and in-depth research on airflow modeling, system mechanism, correlation of spraying parameters, accurate measurement methods in field test conditions, the methods to evaluate spray efficacy, and fully making use of high-precision flight parameters for spraying control. The purpose of this review was to investigate the relationship between the various components of the RW-UAV spraying system for the guidance of fundamental and applied studies in the future. We encouraged more systematic researches in the area of rotor airflow modeling and the optimization of physical parameters of the pesticide application system based on RW-UAV, in the fundamental and applied research areas, to advance the development and application of such systems in agricultural production. At the same time, the paper pointed out some other existing problems in distribution of vehicle components and resources for large payload, physical and dynamic principles and status change of spray droplets in process, flight parameters and their relationships with spray droplets'' moving status, the interaction principles between downdraft of rotors and the crop canopies, the integration of flight parameters and the spray parameters. The fundamental science problems need to have more in-depth investigations in order to fully understand and improve the performance of the pesticide applications based on RW-UAV in agriculture. The authors hope researchers pay more attention to the related research on the pesticide applications making use of the air downdraft of the RW-UAVs from the fundamental and application research aspects, and are closely associated with the current development, applications and issues in the real field conditions. More breakthroughs can be approached from understanding the intrinsic relationship between the rotor control, payload and flight and operational parameters, between the downdraft and the spray droplets, and between the downdraft and the crop canopies. The authors also call for a better collaboration between relevant engineers and scientists to bridge the gap between the engineering applications and the fundamental science in the area of agricultural aerial application and crop protection based on RW-UAV. As the development of RW-UAVs to overcome some current limitations, the authors envision an increasing demand of using them for crop protection in the future.