| The research on plant protection UAV pesticide spraying is different with the gound plant protection machines ,as the pesticide must be sprayed to the best effect, and most or even all of the pesticide must be sprayed onto the target object and absorbed on target surface uniformly; it is not only related to the stability and reliability of the UAV spraying platform but also correlated to the atomizing effect, UAV rotor air flow field,flying height, flying speed, discharge rate, crop features, damage and pest features as well as environmental condition, etc. To study the above points, this paper chooses N-3 oil engine single rotor plant protection UAV(Rotor diameter of 3.1 m) as the research platform,For this parameters that the effect of spraying,such as drop diameter, UAV rotor air flow field, flying height, flying speed, discharge rate and ect, To develop special centrifugal nozzle design and atomization effect research, the rotor flow field width of wind field and the study of the size wind field, the model of the optimal depositional level of the droplet is studied, and combining with the characteristics of crops diseases and insect pests and the rotor flow effect.explores the impact of rotor downward air flow on the temporal and spatial dynamic distribution of crop pests and diseases, provides technical support to improve the UAV pesticide spraying effect in the field and reduce the using of pesticide, and finally makes a contrast experimental research on the pest and disease control by UAV pesticide spraying in the field. The main work covers:1. The structure of centrifugal nozzles are improved, and an experiment is carried out to study the atomizing effect of centrifugal nozzles. The result shows that the optimized centrifugal nozzles is more uniform and steady, it also reflects the rotating speed and discharge rate highly impact the atomizing effect of centrifugal nozzles, the atomized particle size decreases with rotating speed increasing, and increases with discharge rate increasing, but the impact of discharge rate on the atomized particle size is not as significant as that of rotating speed. To reach a favorable coverage rate, the atomized particle size must be 200?m, and the corresponding rotating speed will be 6000rpm. The droplet deposition of centrifugal nozzles is distributed in a hollow circular truncated cone in the whole atomized area. The spraying range is directly impacted by the horizontal speed of droplets; as the spraying range of a single nozzle can reach 2.5m, the nozzles are spaced by at most 2.5m from each other. According to different working heights, the UAV spraying range can reach 5m above.2. This paper studies the rotor air flow field characteristics of N-3 plant protection UAV flying in low altitude by combining numerical analysis and tests, and acquires the rotor air field data in different flying heights. The test result shows that, the simulated value is basically matched with the test value, when the UAV is flying at 5?7m, the wind field breadth is 6-7m, the rotor air flow velocity at the crop canopy is 3m·s-1, and it comply with the principle of air flow terminal velocity.3. To find out the factors impacting the pesticide deposition and the impacting degree in UAV pesticide spraying, and improve the droplet deposition amount on the target object, spraying parameters of the pesticide application equipment and machine are studied by Box-benhnken central composite design principle based on a single-factor test.A mathematical model of quadratic polynomial for the droplet deposition amount is created by using the flying height, flying speed and sprinkler discharge rate as the impacting factor and using the amount of droplet deposition on the target object as the target function to analyze the efficiency of the model and the interaction of factors. The test result shows that, factors impacting the droplet deposition amount are successively the flying height, flying speed, and sprinkler discharge rate; and the optimal combination of spraying parameters is flying height 5.0m, flying speed 3.7 m s-1, double sprinklers discharge rate 1600mL·min-1, in this condition the maximum droplet deposition amount on the target is 56.96%, and the relative error between the test value and the estimated value is within ±7%.4. Based on the above research, By exploring the distribution law of deposition in different parts of the crop and the drift law of droplets at different operating heights of UAV. The practical working parameters of N-3 plant protection UAV are clarified by exploring the rale of droplet deposition on different crop positions and the rule of droplet drift in different UAV flying heights. The test result shows: pesticide is sprayed by N-3 plant protection UAV in the later growing stage of maize, the droplet deposition and uniformity on the plants will be impacted by the UAV flying height and transversal spraying range; and in the comprehensive consideration of droplet deposition characteristics. When the ambient air speed is 3m·s-1 below, the ambient temperature is 25?30?, the relative humidity is 50.9?56.7%, the N-3 plant protection UAV flies at 3-7m, the droplet drift is mainly centralized within an area of 20m away from the sprayed area,and this research result can provide a reference for setting isolating belts in pesticide spraying in the field by N-3 plant protection UAV.5. The impact of N-3 plant protection UAV working on the dynamic distribution of canopy paddy rice delphacidae and powdery mildew spores. The result shows, the distribution of paddy rice delphacidae is significantly impacted by the flying height of UAV; there is no significant impact on the area under the rotor air flow, but the horizontal distribution and vertical distribution of paddy rice delphacidae on crop canopy are changed in the area 2?10m away from the edge area under the rotor air flow. The quantity of paddy rice delphacidae becomes decreased in the crop canopy 2-5m away from the edge area under the rotor air flow,but it is distinctly increased within 5-10m. The distribution of paddy rice delphacidae quantity on the top of crop canopy is distinctly increased by flow disturbance, and the impacted range will be larger if the UAV flies higher and the rotor diameter is larger. In the control of paddy rice delphacidae, simulated flying and spraying of UAV is necessary so that the crop canopy can be disturbed by air flow and paddy rice delphacidae will escape from the bottom part of paddies to other places, it will be more vertically distributed on the canopy, and the control effect can be improved by further spraying. The release of powdery mildew spores is closely correlated to the flow disturbance. In the beginning when not too many spores are released, the UAV rotor air flow doesn't impact the spore release too much; with the increasing of spores,flow disturbance distinctly increases the spore release, by comparing the wheat disturbed by rotor air flow with that not disturbed. For controlling wheat powdery mildew by UAV pesticide spraying and reducing the impact of rotor air flow on spore release, the preventive spraying shall be performed when the spores have appeared for 2-3 days.6. The effect of controlling paddy rice delphacidae and wheat powdery mildew by N-3 plant protection UAV pesticide spraying is studied. The research result shows,The rotor diameter of the single rotor UAV driven by the oil has no significant effect on the test of paddy rice delphacidae control, but the disturbance of air flow and the nozzle selection has no significant effect on it. The protection effect of N-3 plant protection UAV using the optimized nozzle can improve the rice delphacidae control of about 5% after 3 days. The pesticide application effect can be improved more 3% under the disturbance of air flow than under no air turbulence. In the experiment for prevention against wheat powdery mildew,If the optimized nozzle is used,the efficacy of the 7th day of treatment is 55.1% which is better than the effect of nozzle without optimization and the effect of reducing 20% and 40% of the pesticide. When the dosage was reduced by 20%, Its application effect was 46.6% ,and there was no obvious difference in the control effect between knapsack electric sprayer(45.6%) and original nozzle(47.9%). |
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