Research On Droplet Deposition Mechanism And Operating Parameters Of Plant Protection UAV For Rice

At present,aerial spraying of plant protection unmanned aerial vehicle(UAV)for paddy is still at the preliminary stage in C hina.In the application process of aerial spraying of plant protection UAV,the influence mechanism of various factors on the distribution characteristics of droplet deposition is not clear,and the theoretical basis is lacking,which leads to the lack of experimental method guidance and specifications for actual spraying operation of plant protection UAV.In view of this situation,research on droplet deposition mechanism and operating parameters of plant protection UAV for rice was proposed,and the effect of operating parameters,droplet size and wind field below rotor of plant protection UAV on droplet deposition distribution of aerial spraying was studied by combining theoretical analysis and field tests,and flight parameters,flight quality and the effective spraying width of plant protection UAV were compared and analyzed with a series of trials.The main researches and conclusions are as follows:In the study of effects of different operating parameters of plant protection UAV on droplet deposition of aerial spraying in paddy field.The distribution regularity of droplet deposition was obtained by drawing the operation trajectory with Bei Dou Navigation Satellite System carried by one-rotor small unmanned helicopter HY-B-10 L,and analyzing the results of droplet deposition in the target areas and non-target areas.The analysis results showed that: The trends of droplet deposition were similar in the three trials,the parameters of flight height and flight speed both have a great influence on the mean droplet deposition in the collection point of target areas but not significant to the uniformity of droplet deposition.In the target area,the droplets deposition decreases with the increase of the flight height in the three trials.The uniformity of droplets deposition was the best in the flight height of 1.92 m,the best value of uniformity could reach 29%,and was the least in the drift area in this case.In addition,the amount of the droplet deposition in the first and second collection zone were clearly more than the amount of the third collection zone which have a faster flight speed in the target area.While due to the effect of environmental wind field,the amount of droplets deposition and the drift distance of droplets on the left side of flight route were more than the amount of the droplet deposition and the drift distance on the right side of flight route,and with the effect of flight speed,the amount of droplet deposition in the third collection zone on the left side of flight route were more than the droplet deposition in the first and second collection zone on the right side in the drift area.In the study of the effects of different droplet size parameters on droplet deposition distribution and drift of aerial spraying by using plant protection UAV,aerial spraying test with the same spraying rate and different size droplets in rice canopy was carried out by using multi-rotor unmanned aerial vehicle(UAV)MG-1S and four TEEJET nozzles with different aperture.The results showed that,the factor of droplet size had an extremely significant impact on droplet deposition and drift of aerial spraying in rice canopy,and had a significant impact on the droplet penetration.The droplet deposition rate in the upper and lower plant canopy and the droplet penetration in target area increased with the increase of droplet size,and the droplet drift rate and the drift distance decrease with the increase of droplet size.In addition,the average droplet penetration of four different size droplets with Dv0.5 of 95.21,121.43,147.28 and 185.09 ?m in rice canopy were 32.01%,33.48%,37.82% and 38.13% respectively,and the average value of cumulative drift rate were 73.27%,50.26%,35.91% and 23.06% respectively,and the dirft distances were more than 12 m,10~12 m,10~12 m and 8~10 m respectively.Therefore,for the application of plant protection UAV with extra-low volume spraying,in order to reduce droplet drift and improve the droplet deposition effect,the use of droplet with Dv0.5 less than 150 ?m should be avoided and a more than 10 m buffer zone should be considered downwind the spraying field to avoid the drug generated by droplet drift.In the study of effects of wind field below rotor of plant protection UAV on droplet deposition of aerial spraying,the impact on the distribution of droplet deposition by the wind field in X,Y,Z three directions below rotor of single-rotor and multi-rotor plant protection UAV combined with the condition of aerial spraying droplets deposition in rice canopy were analyzed.Among the 3 directions wind field below single-rotor plant protection UAV rotor,the wind field in Y direction had a significant effect on droplet deposition in effective spray area,the wind field in Z direction had an extremely significant effect on droplet deposition in effective spray area.Further more,the wind field in Z direction had a significant effect on the penetrability and uniformity of droplet deposition in effective spray area.The wind speed in Y direction at the edge of effective spray area had a significant effect on droplet drift.In addition,the corresponding correlation coefficient R2 of the regression model which between droplet deposition in effective spray area and the wind speed in Y and Z directions as well as it between the uniformity of droplet deposition in effective spray area and the maximum wind speed in Z direction,were 0.755 and 0.837 respectively,this result can provide a guidance for the actual production application.Among the 3 directions wind field below multi-rotor electric UAV rotor,the wind field in Z direction had an extremely significant impact on droplet deposition in the effective spray area.The wind field in Y direction had a significant impact and the wind field in Z direction had an extremely significant impact on droplet deposition penetration in the effective spray area.The wind field in Z direction had a significant impact on droplet drift.Furthermore,the horizontal wind field in X and Y direction and the vertical wind field in Z direction all affect the deposition uniformity in the effective spray area.With the smaller value of horizontal wind field in X and Y direction and the larger value of vertical wind field in Z direction,the uniformity of droplet deposition is the better,the best value reaching 36.44%.In addition,the corresponding correlation coefficient R2 of the regression model which between droplet deposition in effective spray area and the wind speed of Z direction as well as it between droplet deposition penetration in effective spray area and the wind speed of Y&Z direction,were 0.868 and 0.842 respectively,this models can provide guidance for the practical application.In the study of test and analysis of operating parameters and flight quality of different types plant protection UAV under different control modes,the route accuracy,the variation uniformity of flight parameters and route length of quad-rotro plant protection UAV are better than that of single-rotor plant protection UAV.What's more,the route accuracy,the variation uniformity of flight parameters and route length of quad-rotro plant protection UAV under full-autonomous control mode are better than that of quad-rotro plant protection UAV under semi-autonomous control mode,and the average route deviatio n of quad-rotro plant protection UAV under full autonomous control mode was the minimum,which was 0.172 m.In addition,the effect of flight direction on flight parameters of plant protection UAV under full-autonomous and semi-autonomous control mode were not significant and significant respectively.The effect of route length on flight parameters of plant protection UAV under semi-autonomous control mode were not significant,but it has a significant effect on flight speed of plant protection UAV under full-autonomous control mode.In the study of evaluation and test of effective spraying width of aerial spraying on plant protection UAV,the effective spraying width of single-rotor and multi-rotor plant protection UAV was evaluated with the evaluation method of droplet density and 50% effective deposition amount method by the tests of 12 times with different flight parameters;and different evaluation methods were deeply analyzed.The test results showed that: The evaluation method of 50% effective depositio n amount was more suitable than the evaluation method of droplet density for evaluating the effective spraying width of plant protection UAV 3WQF120-12,which had a relatively larger droplets size,and the average effective spraying width was greater than or equal to 4.44 m.The evaluation method of droplet density was more suitable than the evaluation method of 50% effective deposition amount for evaluating the effective spraying width of multi-rotor plant protection UAV P-20,which had a relatively smalle r droplets size,and the average effective spraying width was greater than or equal to 2.58 m.In addition,the analysis showed that the relative error produced by the software of Deposit Scan was different with the spot image produced by the droplets of different size due to the limitation of current image processing techniques.The relative measurement error of droplet diameter would increase with the droplet size decreasing.Therefore,we should choose the suitable evaluation method for the effective spraying width based on different droplets size of plant protection UAV.