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