Key Structural Blocks Design And Spray Performance Analysis Of Plant Protection UAV

At present,the plant protection UAV used in field crops has been widely adopted and researched in China,while the plant protection UAV applied in orchards is still in the preliminary application and experimental stage.This research takes the four-rotor plant protection UAV as the research object.In view of the problems of heavy load,long axle base and serious spray drift of orchard plant protection UAV,the structural rationality and spray performance of orchards plant protection UAV were studied.The main research contents and conclusions are as follows:Finite element analysis is used to analysis the mechanical properties of key structures of plant protection drones.The results show that the rotor spider,motor,griping t-tube,pipe-griping for water tank and lower brackects meet the strength requirements under the corresponding working conditions.However,the lateral folding of the rotor arm may be plastically deformed under full load take-off conditions.Multi-objective optimization design of thickness and length of transversely folded pipe clamps by response surface analysis.The results show that the deformation is reduced by 6.77% and the maximum equivalent stress is reduced to 216.37 MPa,which meets the mechanical performance requirements.Combined with orthogonal test,the influence of nozzle spray angle,height and pressure on the spray width was discussed by analysis of variance.The results show that the nozzle spray angle has the greatest influence on the effective spray width,and the spray height has the least influence on the effective spray width.The effect of different nozzle spray angles(–15°,0°,15°)on droplet deposition density was analyzed.The results show that the variation coefficient of droplet deposition density is between 10% and 15% at spraying angle of –15° and 28.98% at spraying angle of 15° and the distribution of droplets is relatively uneven.Aiming at the serious problem of droplet drift in plant protection UAV operation,the influence of spray angle on droplet drift under different cross wind velocities(1m/s,2m/s,3m/s,4m/s and 5m/s)was analyzed.The results show that when the crosswind speed is less than or equal to 2m/s,adjusting the spray angle of the nozzle can significantly reduce the drift of droplets,and the drift rate of droplets can be reduced by 30%.When the crosswind wind speed is greater than 3m/s,the effect of adjusting the spray angle of the nozzle on the drift of the droplet is not significant,and the drift rate of the droplet is still higher than 75%.