Spraying Quality Evaluation On Plant Protection UAV

The usage of agricultural UAV developed quickly worldwide in recent years.But there are also many problems on the spraying system,spraying quality and the evaluation index of the spraying quality.In this paper,we proposed four spraying quality evaluation indexes,containing deposition rate,spraying uniformity,droplet penetration and droplet drift rate.The factors effect on spraying quality and droplet drift of UAV were studied and the influence of spray volumes on droplet deposition and field efficacy were analyzed in wheat and cotton fields.The main research contents and conclusions are as follows:The spraying system has a key effect on the spraying quality.In the lab,we used the Laser Particle Analyzer to analysis the droplet sizes of the different nozzles mounted on the typical UAVs.The results show that the droplet size are in the range of F-VF with the standard nozzles mounted on the UAV,which have a high drift risk.Under the same flow rate,the IDK nozzles spray bigger droplets and have a better anti-drift performance than LU nozzles.A power exponential function relationship was found between the droplet size and the rotating speed of the rotary cup of the centrifugal nozzle.The different adjuvants and pesticide formulations have different effects on the hydraulic nozzles and centrifugal nozzle.For hydraulic nozzles,most adjuvants and pesticide formulations can increase the droplets size.On the aspect of spraying uniformity,we test the influence of opening angles,spray pressure and the spraying height on the spray distribution of the hydraulic nozzles using a spray patternator table.The spray pattern coefficient of variation(CV)was calculated from the simulated according to the single-nozzle application with different nozzle interval.The results indicate that the CV firstly decreases and then increases with the increase in the interval of two LU12002 nozzles.When the distance between the two nozzles was 125 cm,the CV will be the lowest of 9.7%.In the field,the effect of spraying height on deposition under single-pass application was studied.An innvoation evaluation method of spraying swath was created by calculating the CV of the simulating field distribution according to the single-pass application with the pattern centerline being moved a distance.In our test,we take CV<30%as the appropriate acceptable coefficient of variation(CV)to evaluation the effective swath width.And this method was verified by testing the CV under multiple-pass application.On the aspect of spraying penetration,the cotton was selected as a test plant.The effect of flight height(1.5m,2m and 3m),flight speed(3m/s,5m/s,and 7m/s)and droplet size(100?m,150?m,200?m)on droplet penetration were tested in the cotton field with P20 UAV.The deposition and defoliation results indicate that the droplet size of 150?m would be the most suitable droplet size on defoliation application.On the aspect of droplet drift,the wind tunnel and field experiment were conducted to analysis the main factors affecting the droplet drift including droplet size and wind speed.The motion equations of droplets in the wind tunnel and field with UAV application were established.From the wind tunnel test results,the drift rates were centrifugal nozzle>LU hydraulic nozzle>IDK hydraulic nozzle.For the hydraulic nozzles,a non-linear statistical drift prediction equation was established.The drift prediction equation with the dependent variable of drift rate and three non-correlated independent is as follow: Q_h=2.28-1.20 ln(D_l)-0.0057 D_s+0.89W_sWhere,Q_h:Drift rate(%);D_l:Downwind drift distance parallel with wind direction(m);D_s:Droplet size(?m);W_s:Wind speed(m/s).Spray adjuvants have a significant effect on anti-drift.For hydraulic nozzle,adding adjuvants can reduce the drift of 24.1-66.4%;For centrifugal nozzle,adding adjuvants can reduce the drift of 0.68-50.8%.In all adjuvants,modified vegetable oil Beidatong?has the best anti-drift effect.In the field,the experiment was conducted in Xinjiang region with P20 UAV.The effect of different droplet sizes(100?m,150?m,200?m)and wind speeds(0-3.81m/s)on drift rate were studied.Non-linear mathematical drift prediction equation was established based on ground deposition data at different downwind distance of 15treatments.The drift prediction equation with the dependent variable of the amount of the deposition and three non-correlated independent is as follow: D_p=exp(-D_t/4.4)×(0.042W_s-7.2×10^-4D_s+0.20)Where,D_p:Downwind drift(?g/cm²);D_t:Downwind drift distance parallel with wind direction(m);D_s:Droplet size(?m);W_s:Wind speed(m/s).An R²of 0.83 indicated a good coincidence between the measured drift and predicted drift.Field efficacy is one of the most important evaluation indexes of plant protection UAV application.The spray volume is the most significant difference between UAV and conventional sprayer.In consequence,two field's experiments to study the effect of spray volumes on deposition and field efficacy were conducted in the wheat field of Xinxiang,Henan province and the cotton field of Shihezi,Xinjiang region.In the wheat field,a3WQF120-12 plant protection UAV was used to spray different kinds of pesticide to control wheat aphids and powdery mildew.When the systemic pesticides were sprayed,the spray volume larger than 16.8 L/ha has a good control effect,but for contact pesticides,the spray volume larger than 28.1 L/ha will be better.In the cotton field,a multi-rotor P20 UAV was used for cotton defoliation application.Considering the spray deposition,defoliation rate and the working efficiency,a spray volume of 15.0 L/ha is thus recommended to the farmers for UAV application.