Indoor Test Platform Design And Experiments Of Droplet Deposition Effect For Plant Protection UAV

The UAV for plant protection spraying operation has been gaining more and more attention and popularity in China due to its high efficiency,low cost and without geographica l restrictions.It is widely used in hil s,mountainous regions,plains,etc.Operating objects include Rice,wheat,corn,cotton,soybeans,and orchard crops such as citrus,apple,grapefruit,and betel nut crops.The UAV for plant protection consist of single rotor,mult i-rotor,fixed wing,oil-dynamic,electric and combinations of different types,which have made rapid progress in the field of agricultural plant protection in China.The effectiveness of UAV for plant protection spraying is not only related to the performance of the whole UAV,but also related to the operating parameters of UAV spraying and external environme nt.Therefore,UAV for plant protection spraying operation is a comprehensive technology.It needs to consider the combination of agricultural machinery and agronomy.Different types of UAV and spray operation parameters need to be selected for different work fields and operating objects.In this dissertation,the contrast experiments of droplet deposition in indoor and outdoor environment of UAV are carried out.The experimental factors include flight height（1m,1.5m,and 2m from crop canopy）,rotor wind field（rotor wind field under 3L,6L,9L-load）,nozzle model（LECHLER 01#,015#,02#fan nozzles）,horizontal distance from the nozzle to the center of the rotor（along the arm direction-16cm,0,+16cm）.Four-factor and three-level orthogonal tests are carried out to investigate the distribution and distribution of fog droplets,moreover,spraying quality evaluation and parameter optimization are conducted.The main tasks include:1.Design and build an experimental platform for indoor droplet deposition,which can accurately adjust the platform speed,height,and control the rotor wind field.By changing the pulse frequency and number of stepper motor controllers to control the moving speed of the track trolley,the track trolley drives the mounted UAV to move horizontally.The lift ing device can accurately change the platform height,and the drone’s throttles can be controlled accurately to change the spin velocity of the rotor,thus changing the downwash wind field of the rotor.The track trolley’s operating speed ranges from 0-1.5m/s,the platform height adjustment ranges from is 2-3m（the height of the drone’s nozzle is calculated from the ground）,and the rotor wind field is quantified with the rotor lift force.A single rotor’s lift force can be changed from 0N to 100N.2.Particle size analysis of different fan-shaped nozzles（LECHLER 01#,015#and 02#）to obtain the droplet volume diameter(D_V50)values of 02#（149.64mm）,015#（133.02mm）,01#（102.07mm）.From the droplet size distribution span（S）and the percentage of size less than 150mm accounted for the total volume of mist particles,015#nozzle is more suitable for UAV for plant protection spraying operations;for single rotor wind field test under indoor environment,the result shows that the relationship between the throttle of the remote controller and the motor speed（idling）is linear,and the fitting relationship function is y=48.18x+34.51.The relationship between the throttle and the single rotor lift is cubic,and the fitting relationship function is y=-1.41E-4x³+0.03x²-0.1x+0.28,where the throttle section（30%-90%）is in a linear relationship with the lift of the single rotor,the fitting function is y=1.29x-23.44.3.In the comparative analysis of the indoor and outdoor droplet deposition experiments,it was found that the particle size distribution of droplets was consistent with the particle spectrum analysis in the static environment.The size of the droplet medium diameter(D_V50)classified by nozzle type was 02#>015#>01#.The diameter of droplets in laboratory tests is significantly smal er than that of outdoor experiments;the effective spray swath width is between-2.5².5m,and the influence of outside wind on the effective spray swath width is significant;In the contrast analysis of droplet deposition density,the indoor droplet deposition effect is better than that In outdoor tests,the droplet deposition density was peak-like and the peak was at the mid-point between the two rotors.The outdoor experiment was disturbed by the outside wind,and the peak value was shifted to the downwind direction.The nozzle type significantly influences the droplet deposition density,and the severity is01#>015#>02#.In the comparative analysis of droplet deposition volume,the rotor wind field has a significant effect on the deposition volume,and the outdoor test deposition volume is greater than the indoor test,and the external wind can increase the amount of droplet deposition.In the comparative analysis of the uniformity of droplet deposition,for both the indoor and outdoor tests,the droplet distributions of the upper,middle,lower layer are uniform,and the indoor experiment of the uniformity of droplet deposition in the upper and middle layers was superior to that of outdoor experiment,meanwhile,the outdoor experiment of the uniformity of droplet deposition in the lower layer was superior to that of indoor experiment.The rotor wind field has a significant impact on the uniformity of droplet deposition;in the contrast analysis of the droplet deposition penetration,the CV values on the indoor and outdoor test collection belts are in an“M”shape distribution,The penetrability of the middle and the edge of the droplet is greater than the penetrability directly below the rotor,and the flying height has a significant effect on the penetrability of the droplets.4.In the range analysis of indoor and outdoor droplet deposition,the analysis indexes of droplet deposition density,deposition volume,uniformity,and penetrability of indoor and outdoor tests were analyzed,and the parameters of different evaluation indexes were optimized and performed the influencing significance comparison.In the indoor test,the optimum operating parameter combination was A3B2C1D3（the flight height was 2m from the crop canopy,the rotor wind field was under 6L load condition,the nozzle type was 01#,and the distance from the center of the nozzle to the center of the rotor was along the length of the arm.16cm）,The order of the influencing factors is flight height>nozzle type>rotor wind farm>nozzle distance from rotor center;in outdoor test,the optimal operating parameter combination was A3B2C1D3(fly height is 2m from the crop canopy,rotor lift was under 6L load condition,the nozzle type is 01#,and the distance from the center of the nozzle to the center of the rotor is 16cm along the length of the arm.The order of the influenc i ng factors is flight height>nozzle type>nozzle distance from rotor center>rotor wind farm.The result of range analysis shows that the indoor result is almost the same as the outdoor result.The flight height is extremely significant to the spraying operation with the optimal value is2m from the canopy,the loading is 6L,and the nozzle is selected as 01#fan-shaped nozzle.The installation position of the nozzle is along the arm horizontally outward 16cm,this combination is most suitable for operation.Through the comparison and analysis of indoor and outdoor droplet deposition tests,it is concluded that since the indoor test is not influenced by the outside wind interference,the operation quality is better than the outdoor test.Moreover,for the operating parameters optimization,the optimal parameters of indoor and outdoor tests are consistent,The order of the influencing factors of operating parameter is also almost the same,so the constructio n and experimental research of indoor droplet deposition test platform is significant,which can provide guidance for the actual operational parameter optimization.