无人机用气力式喷粉装置设计及作业效果分析

Design of pneumatic powder spraying device for unmanned aerial vehicle and analysis of operation effect

林业病虫害是危害森林健康及其生态系统作用的主要原因之一。目前,我国针对橡胶树这类高大乔木的施药方式多为传统的地面喷雾和喷粉机械,该类作业方式受地形限制、人力需求大、劳动效率低,且难以对高处冠层施药。当前用于无人机挂载的喷粉装置多为地面喷粉器械的简单搭载,这易造成粉剂堵塞,喷施均匀性难以保证。为改善当前喷粉作业的效果,本研究设计了一种搭载在无人机上的气力式喷粉装置,利用高速气流将粉剂沿管道吹出,并对关键部件进行模拟仿真。结果表明,对于本研究设计的气力喷粉管道,涵道风机风速达10 m/s可满足绝大多数粉剂的输送要求。以飞扬倾角和飞扬高度为评价指标,模拟了不同安装位置下无人机喷粉作业的效果,模拟分析表明,为更好地抑制粉剂飞扬,气力喷粉装置的喷粉出口应正处旋翼下方,并后置安装在无人机上,其飞扬倾角为84°,飞扬高度为0.6 m。为探究试验样机的作业参数对喷粉沉积覆盖率、均匀性与穿透性的影响,开展了喷粉流量、作业高度与飞行速度3因素3水平的正交试验,结果表明,沉积覆盖率最佳作业参数为:喷粉流量6.0 kg/min、作业高度2 m、飞行速度2 m/s。沉积均匀性最佳作业参数为:喷粉流量3.6 kg/min、作业高度2.5 m、飞行速度6 m/s。沉积穿透性最佳作业参数为:喷粉流量6.0 kg/min、作业高度2.5 m、飞行速度4 m/s。为获得最优的试验方案,采用模糊综合评分法进一步分析,结果表明,最佳作业参数为喷粉流量6.0 kg/min、作业高度2.5 m、飞行速度2 m/s,相应的喷粉覆盖率均值为14.06%,喷粉均匀性均值为34.81%,喷粉穿透性为5.61%。因此,本研究的气力式喷粉无人机进行植保作业时,需结合实际作业对象,对沉积覆盖率、均匀性、穿透性不同需求综合分析,合理选择无人机喷粉的作业参数。研究结果可为高大乔木病虫害关键防治设备的研发提供新思路,对实现林业精准病虫害防治具有重要价值。

Forestry pests and diseases are significant contributors to the endangerment of forest health and its ecosystem.Currently,the predominant application methods for tall trees such as rubber trees in China are mostly traditional ground spraying and powder spraying machinery.Such operation methods are limited by terrain,large manpower demand,low labor efficiency,and difficult to be applied to the high canopy.Presently,most powder spraying devices for UAV mounting are simple adaptations of ground powder spraying devices,which often encounter issues such as powder blockage and difficulty in ensuring spraying uniformity.In order to improve the effect of current powder spraying operation performance,this study designed a pneumatic powder spraying device loaded on the UAV,which used high-speed airflow to blow powder out along the pipe and simulated the key components.The results showed that,for the pneumatic powder spraying pipe designed in this study,the wind speed of the bypass fan reached 10 m/s,which can meet the requirements of most of the powder delivery.Using the flying angle and flying height as evaluation indexes,the effect of UAV powder spraying operation under different installation positions was simulated.The simulation results indicated that,for optimal suppression of powder dispersion,the pneumatic powder spraying device's outlet should be positioned beneath the rotor and mounted onto the UAV afterward.The recommended flying parameters were a flying angle of 84°and a flying height of 0.6 m.To explore the effects of operation parameters of the test prototype on the powder deposition coverage,uniformity and penetration,an orthogonal test was carried out with three factors and three levels of powder flow,operation height and flight speed.The results showed that the optimal operation parameters for deposition coverage were the powder flow of 6.0 kg/min,operation height of 2 m,and flight speed of 2 m/s.The optimal operation parameters for deposition uniformity were the powder flow of 3.6 kg/min,operation height of 2.5 m,and flight speed of 6 m/s.The optimal operation parameters for deposition penetration were the powder flow of 6.0 kg/min,operation height of 2.5 m,and flight speed of 4 m/s.In order to obtain the optimal test scheme,the fuzzy comprehensive evaluation method was used for further analysis.The results showed that the optimal operation parameters were the powder flow of 6.0 kg/min,operation height of 2.5 m,and flight speed of 2 m/s.The corresponding average powder coverage was 14.06%,powder uniformity was 34.81%,and powder penetration was 5.61%.Therefore,when the pneumatic powder UAV was used for plant protection operations,it was necessary to comprehensively analyze the different requirements of deposition coverage,uniformity,and penetration,and reasonably select the operation parameters of UAV powder spraying.This study can provide new ideas for the research and development of key equipment for the prevention and control of tall tree diseases and insect pests,which has important value for the realization of precise forest disease and pest control.