Effects of spray adjuvants and operation modes on droplet deposition and elm aphid control using an unmanned aerial vehicle

A conventional spraying mode and a fully autonomous fruit tree operation mode using a model DJ T30 unmanned aerial vehicle(UAV)were used to control aphids control on elm trees and to clarify the distribution of droplets in elm trees sprayed by a UAV.The effects of six aviation spray adjuvants on elm canopy droplet deposition and aphid control were evaluated.ImageJ software was used to analyze and measure the droplet density and deposition of water sensitive paper in two modes;this was done to calculate the droplet uniformity,depositional penetration,and droplet penetration,and to verify the aphid control effect.The results showed that the droplet density increased by 79.7%-100.7% in the upper canopy and 0-394.1%in the lower canopy without adjuvants in the fully autonomous fruit tree operation mode.The upper canopy deposits increased by 65.7%-179.3%,and the lower canopy increased by 0-152.8%.When adjuvants were added,the droplet density in the upper canopy increased by 49.7-56.1%using Jiexiaofeng(JXF),and the lower canopy increased by 138.2%-177.8% using JXF,45.8%-141.3%using Beidatong(BDT),45.5%-92.9% using Gongbei(GB),0-93.5% using Maisi(MS),and 0-95.2%using Manniu(MN).The deposits of the upper canopy increased by 888.1-1154.2% using JXF,0-1298.3% using MN,0-343.9%using BDT,0-422.5% using GB,0-580.3% using MS.The lower canopy increased by 746.4%-1426.0%using JXF,226.2%-231.0% using BDT,435.8%-644.0% using GB,255.0%-322.4%using MS,and 249.3%-360.0%using MN.When JXF was added,the droplet uniformity,droplet penetration and depositional penetration were better than when using other adjuvants.The effects of JXF,BDT and GB in controlling aphids was significantly better than other adjuvants(p<0.05).The following control effects were observed;94.1% with JXF,93.1% with BDT,and 93.3% with GB after 3 d of application,and 97.9% with JXF,95.6% with BDT,and 97.1% with GB after 7 d of application.At the same time,the application of the fully autonomous fruit tree operation mode and JXF can effectively improve the density and deposits,which will produce a superposition optimization effect.Our study focuses on the prevention and control of elm aphid infestations based on the operation mode of a UAV and aviation spray adjuvants,which can provide a baseline for the control of diseases and insect pests using UAVs in agriculture and forestry.

Effect of wind field below unmanned helicopter on droplet deposition distribution of aerial spraying

Wind field is one of the important factors affecting the distribution characteristics of aerial spraying droplet deposition.In order to reveal the impact mechanism of droplet deposition distribution by the wind field below agricultural unmanned helicopter rotor,in this study,the wind field distribution below uniaxial single-rotor electric unmanned helicopter rotor was measured by using a wireless wind speed sensor network measurement system for unmanned helicopter.The effects of wind field in three directions(X,Y,Z)below the rotor on droplet deposition distribution were analyzed with the condition of aerial spraying droplet deposition in rice canopy,and the regression model was established via variance and regression analyses of experiment results.The results showed that,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,and the corresponding significance(sig.)values were 0.011 and 0.000.Furthermore,the wind field in Z direction had a significant effect on the penetrability and uniformity of droplet deposition in effective spray area,the corresponding sig.values were 0.025 and 0.011 respectively.The wind speed in Y direction at the edge of effective spray area had a significant effect on droplet drift,the sig.value was 0.021.In addition,the correlation coefficient R of the regression model was 0.869 between droplet deposition in effective spray area and the wind speed in Y and Z directions,and 0.915 between the uniformity of droplet deposition in effective spray area and the maximum wind speed in Z direction.The result revealed the influencing mechanism of the wind field below the rotor of uniaxial single-rotor electric unmanned helicopter on the distribution of aerial spraying droplet deposition.The results can provide guidance for the actual production application of aerial spraying to reduce liquid drift and improve the utilization rate of pesticide.

Influence of UAV flight speed on droplet deposition characteristics with the application of infrared thermal imaging

A plant protection unmanned aerial vehicle(UAV)applied for spraying pesticide has the advantages of low cost,high efficiency and environmental protection.However,the complex and changeable farmland environment is not conductive to perform spray test effectively.It is therefore necessary to carry out spray test under controlled conditions.The current study aimed to illuminate the variation law of droplet deposition characteristics under different UAV flight speeds,and to verify the feasibility for applying infrared thermal imaging in detection of droplet deposition effects.A UAV simulation platform with an airborne spray system was established and an analysis program Droplet Analysis for dealing with water-sensitive paper was developed.The results showed that,when the flight speed was set at 0.3 m/s,0.5 m/s,0.7 m/s,0.9 m/s and 1 m/s,respectively,the droplet deposition density,droplet deposition coverage and arithmetic mean of droplet size D0 decreased as the UAV flight speed increased.On the contrary,the droplet diameter variation coefficient CV increased with the increase of UAV flight speed,resulting in the worse uniformity of sprayed droplet distribution as well.The results can provide a theoretical support for optimizing the spraying parameters of plant protection UAV,and demonstrate the practicability of infrared thermal imaging in evaluating the droplet deposition in the field of aerial spraying.

Evaluation of droplet deposition and effect of variable-rate application by a manned helicopter with AG-NAV Guía system

The variable-rate application is an important aspect of precision agriculture.In order to determine the regular patterns of droplet deposition and compare the actual variable-rate spraying effect of the AS350B3e helicopter with the AG-NAV Guía system,spray tests were conducted with different operating parameters and operating methods.In this study,the deposition distribution of droplets in the effective swath area was evaluated for six single-pass applications at four different flight velocities.The effects of adding adjuvant on droplet deposition,drift and droplet size were compared,and the actual variable effect of the forth-back application was verified.The analysis results showed that the position of the effective swath area was affected by natural wind velocity and wind direction,and would shift to the downwind direction area from the helicopter route of a different degree.The effective swath width increased slowly and then decreased sharply with the increase of flight velocity.It was found that flight velocity of 100 km/h was the peak inflection point of effective spray width variation.Moreover,the effect of flight velocity on the distribution uniformity of droplet deposition in the effective swath area was not significant.In the single-pass application of 90 km/h,adding adjuvant could increase droplet size in the effective swath area.The deposition increased by 8.98%,and the total drift decreased by 28.65%,of which the upwind drift decreased by 28.31%and the downwind drift decreased by 29.06%.In the forth-back application of 90 km/h,the error between actual application volume and system setting dose was 12%.The results of this study can provide valuable references for future research and practices on variable-rate aerial applications by manned helicopters.

Effects of droplet size and spray volume parameters on droplet deposition of wheat herbicide application by using UAV

With the characteristic of flexible and precise,unmanned aerial vehicles(UAVs)for low volume applications are increasing substantially and quickly around the globe.However,little attention has been paid to the study of wheat herbicides with UAV,especially the research on the spray volume and droplet size of the herbicide sprayed by UAVs.The objectives of this study were to compare the droplet deposition from a typical commercial UAV under four different spray volumes of 7.5 L/hm2,15.0 L/hm2,22.5 L/hm2,and 30.0 L/hm2 and three different volume median diameter(VMD)of 150μm,200μm,and 300μm during winter wheat weeding period.DepositScan software was used to analyze droplet deposition parameters including the percentage of spray coverage and the number of droplets in various sampling positions.The test results showed that the droplet deposition waseffected by each factor andtheirinteractions.When the spray volume was 7.5 L/hm2,the effect of VMD on the percentage of spray coverage was not significant.However,these variation rules were changed to smaller droplets with greater coverage when the spray volume higher than 15.0 L/hm2.In all treatments,the number of droplets increased with decreasing VMD or increasing spray volume.The maximum percentage of spray coverage and the number of droplets that were achieved under the VMD of 150μm and the spray volume of 30.0 L/hm2 were 12.8%and 40.0 droplets/cm2,respectively.The variation coefficients of the percentage of spray coverage and the number of droplets were 29.0%-73.3%and 20.2%-54.1%,respectively.The most uniform deposition was achieved under the spray volume of 15.0 L/hm2and the VMD of 150μm.The results revealed the effect of droplet size and spray volume parameters on droplet deposition,which was useful for guiding farmers on how to use UAVs for weeding in winter wheat fields.

Nozzle test system for droplet deposition characteristics of orchard air-assisted sprayer and its application

In order to obtain nozzle droplet deposition characteristics for sprayer mechanical design and variable spraying control algorithms,a nozzle droplet deposition characteristics test system for air-assisted spraying was designed.The test system can supply a stable wind site with precisely controlled air speed whose speed control ranges from 2 m/s to 16 m/s with maximum relative error of 4.5%.It can spray out a certain amount of liquid pesticide with adjustable spraying pressure which can be controlled with high precision while the maximum relative error is only 1.33%.The distribution of droplet deposition can be collected and measured by using the acquisition device and a pesticide deposition optical measurement system.The experiment of two-dimensional nozzle flow measurement was carried out.The results show that nozzle flow distribution is uniform and symmetric with“double-hump”shape in the spray range.Multi-nozzle overlapped droplet deposition ranges from 85%to 116%relative to the average.The nozzle droplet deposition experiment was completed.The experiment results show that in air-assisted spraying,the higher the wind speed,the less droplet deposition is affected by gravity.When the wind speed is higher than 12 m/s and spraying distance is 0.80 m,droplet deposition is concentrated on the originally designated point and hardly affected by gravity.The horizontal spray width becomes smaller with higher wind speed.When the wind speed is high,it can be considered that nozzle deposition only focuses on the nozzle center,if the position requirement is not very high in orchard spraying.

Effects of plant protection UAV-based spraying on the vertical distribution of droplet deposition on Japonica rice plants in Northeast China

In order to study the regularity of the vertical distribution of droplet deposition on rice plants during pesticide spraying operated by a low-flying multi-rotor plant protection unmanned aviation vehicle(UAV),water-sensitive spray cards were placed on the leaves at the top,in the middle,and at the bottom of rice plants to acquire data on droplet deposition.In this study,a suspension containing tricylazole and hexaconazole was used in the spraying.The water-sensitive spray cards were analyzed by the droplet deposition processing software iDAS to obtain the vertical distribution of the droplets sprayed by the plant protection UAV.The results showed that (1)significant variation was found in the coverage of the droplets in different vertical positions of the rice plants.Within the effective spray width,the best coverage of the droplets was found in the area just below the rotors,whereas the coverage of areas farther away from the rotors was poor.For the different vertical positions of the rice plants,the overall droplet coverage was 58.38%at the top,33.55%in the middle,and 11.34%at the bottom of the plants;(2)for all vertical positions,the average size of the droplets ranged between 110μm and 140μm,which was suitable for the control of plant diseases and insect pests.The highest droplet density was found at the top of the plants,and the distribution of the droplet density was similar in the middle and at the bottom of the rice plants;(3)the diffusion ratio at the top of the rice plants(0.84)was better than that in the middle(0.57)and at the bottom(0.37).The overall relative span could meet the requirements for the actual application.Except for the position in the middle of the plants,the relative span for the other positions of the plants was over 0.67,which is the standard value.This study demonstrated the distribution regularity of droplet deposition along with the vertical direction of rice plants during UAV-based spraying,which is of guiding significance for the use of UAVs in plant protection,the improvement of chemical utilization efficiency,and the reduction of pesticide and fertilizer pollution.

Tunnel-convective air-assisted spraying technology for improving droplet deposition on hedgerow vines

Given the impermeability,larger dosage,and higher drift of pesticides used in modern hedgerow vine canopies,a novel tunnel-convective air-assisted spraying technology was proposed.Mechanized spraying equipment with high penetration and low drift was developed.The air-assisted system of this equipment was centrosymmetric,and the fan type was cross-flow.The fan outlet width was 138 mm and the air duct’s main body followed a logarithmic spiral profile,based on parallel flow theory.The external diameter of the impeller was 157 mm,which was fixed into a barrel structure by 23 strong forward-curved blades,each being 1 mm thick.The central angle of the blades was 108°,and the ratio of the internal and external diameters was 0.81.The impeller and air duct served as guides to circulate and reciprocate airflow around the crown,forming a tunnel-convective air-assisted to the vine.Using MATLAB interpolation,the airflow trajectory of the air convection circulation in the door-shaped cover was obtained.The velocity field distribution test showed that,in the case of a canopy,there were tunnel-convective circulating airflows with high velocity on both sides and uniform velocity in the middle of the canopy.Due to the tunnel-convective air-assisted spraying technology,the vertical distribution uniformity of spray deposition has been significantly improved,spray penetration has been enhanced,penetrability has been effectively improved,and droplets on the ground and in the air have been significantly reduced.The results of this study can assist in providing further optimization and improvement of plant protection machinery.The new tunnel-convective air-assisted spraying technology may be a more favorable choice for future spray applications and the environment.

Effects of flight parameters for plant protection UAV on droplets deposition rate based on a 3D simulation approach

With the development of aviation agricultural technology,the number of farmers adopting the use of drones in daily agricultural activities is growing rapidly in recent decades.Among these,a large portion constitutes agricultural drones being used in pest control and crop protection practices,e.g.agriculture spraying of pesticides.Spraying pesticides with drones have proven to be faster than other traditional methods.On the downside,flight time and range of Unmanned Aerial Vehicles(UAV)are often limited.Thus,a proper arrangement of flight height and velocity will greatly improve spraying efficiency.A new strategy to optimize the flight parameters,i.e.flight height and flight velocity,for fixed-wing UAV with a 3D simulation-based approach together with an automatic optimization algorithm was proposed in this study.To find the optimal parameters for a UAV to fly and spray under certain environmental conditions,a three-dimensional model of the target crop was established first,followed by a detailed simulation of droplet spraying.As a demonstration case,a grass model was developed and used as the target plant,and a physics-based method was used to simulate realistically the movement of the droplets in the air as well as the interaction between the droplets and the plant to obtain the droplet deposition rate under the specified operating parameters.Furthermore,the standard Particle Swarm Optimization(PSO)algorithm was used to optimize the UAV operating parameters to obtain the best operating parameters.The results indicate that using the standard PSO algorithm to optimize the operating parameters of the drone could significantly improve the deposition rate and find the best operating parameters.

Droplets movement and deposition of an eight-rotor agricultural UAV in downwash flow field

The movement and deposition of the droplets sprayed by agricultural unmanned aerial vehicle(UAV)are influenced by the complex downwash flow field of the rotors.Instead of conducting field experiment,a high speed particle image velocimetry(PIV)method was used to measure the movement and deposition of the droplets at different rotating speeds of rotors(1000-3000 r/min)or at different transverse injecting points(20-50 cm away from its nearby rotors)in the downwash flow field of an agricultural UAV with eight rotors and conical nozzles.The maximum speed and size of the high speed zone of the droplets were found greatly influenced by the downwash velocity.The initial spray angle of the nozzle declined with the increase of downwash flow speed.It was found that the downwash velocity could not only change the deposition zone of the droplets,but also influence their distribution.The increase of the downwash velocity would increase the deposition uniformity of the droplets.The nozzle position in the downwash flow field could also influence the deposition of the droplets.When the transverse distance between the nozzle and its nearby rotors increased,the relative deposition near the downwash flow of the rotors increased simultaneously.However,the distance between the deposition peak and the nozzle stayed constant.The initial spray angle of the nozzle was not influenced by the transverse distance between the nozzle and its nearby rotors.The research results could provide a theoretical basis and reference for the optimization of the spray application of multi-rotor UAV to minimize droplets deposition uncertainty.

Simulation and experimental research on droplet flow characteristics and deposition in airflow field

In order to study the motion law of droplet flow under the airflow action of long-range air-blast sprayers,a CFD-based 3D model was established for the air-blast sprayer duct and its external airflow field,and the discrete phase model was introduced to simulate the motion of droplet flow in the airflow.The simulation data of the droplet flow trajectory,droplet flow parameters and droplet deposition were obtained by establishing the monitoring sections and bilateral coupling calculation in the airflow field.Results showed that gravity had an obvious effect on droplets and large droplets settled faster.Some of the larger droplets were formed by polymerization in droplets motion.The smaller droplets were transported further along with the airflow,and the long-range sprayer has a significant effect on the directional transport of small droplets.Besides,the spraying swath in the direction perpendicular to the range enlarged gradually with the increase of the spraying range.At the end of the range,the diffuse and drifting of the droplets were dominant.Given that the outlet airflow velocity of the sprayer duct was 25.01 m/s and the spray pressure 1.8 MPa,the maximum motion distances of aerosol,mist,fine mist and coarse mist in the airflow field were 18.5 m,19.5 m,17.5 m and 10.5 m,respectively.Droplet size and number as well as number density and volume density of droplet flow on all monitoring sections showed a regression function with changes in the distance of the spraying range.The simulation results of the model adopted in this paper were verified by Chi-square test between the simulation results of the droplet deposition and the spray measurement results.Research results provide a new method for the study of orchard air-blast spraying technology and references for the optimization of spraying technology.

Simulation and visualization of spraying droplets behavior and deposition within virtual rice canopy

Models for accurately simulating pesticide droplet deposition and transmission mechanism in rice canopies can provide an effective and economic tool to optimize methods for spraying pesticides,adjuvant formulation,and spray parameters.However,the current studies on the modeling of spray droplet deposition within rice plants are still very limited.Aiming at this problem,a method to model and visualize spray transmission and deposition within the canopy of rice plants was proposed.Firstly,a particle system was used to simulate the spraying scene of droplets.Then an improved method to determine the behavior of rebound and shatter of the droplets in the virtual scene was proposed.The deposition of spraying droplets on a leaf was calculated according to the inclination angles of the leaf,the characteristics of the leaf surface,and the physical and spatial characteristics of the droplets.The experiment shows that the method can simulate the behavior of the spraying droplets within a virtual scene of a rice plant,which may provide a reference for the study of spray deposition in the canopy of the crop.

Design of a high-voltage electrostatic ultrasonic atomization nozzle and its droplet adhesion effects on aeroponically cultivated plant roots

In the process of aeroponics cultivation,the atomizer is one of the most important influencing factors on the cultivation process.This study presented the design of an ultrasonic atomization nozzle using contact charging and a root droplet adhesion test rig.The purpose of this study was to reveal the relationship between the main operating parameters of the high-voltage electrostatic ultrasonic atomization nozzle and the atomization effect using droplet adhesion measurements.In this study,the ultrasonic effect of nozzle was achieved by using Laval tube,and the design of the key parameters for the high-voltage electrostatic ultrasonic atomization nozzle were inlet pressure,electrostatic voltage root core electrode material and spray distance;the droplet size variation and root adhesion patterns were obtained through experiments.The best operating parameters were analyzed by using the orthogonal test method,and the droplet deposition distribution of the root system at different scales was investigated in the atomization chamber.The test results revealed that when the root core electrode material was coppe and the nozzle working parameters were at 0.4 MPa of inlet pressure,at 1.75 m the spray distance,at 12 kV of the electrostatic voltage,the root system has the highest droplet adhesion.

Droplets deposition and harvest-aid efficacy for UAV application in arid cotton areas in Xinjiang,China

With the development of Unmanned Aerial Vehicle(UAV)sprayers,the application of low-volume spraying of harvest-aid and other agrochemicals to cotton using UAVs is becoming a new agronomic trend worldwide.The effect of spray volume and canopy density for UAV spraying is significant but was rarely studied.In this study,five representative spray volumes were explored to examine the effect of spray volume on deposition and harvest-aid efficacy for cotton using a UAV sprayer.To explore the effect of canopy density,similar tests were carried out in a field located nearby with a lower leaf area index(LAI).A conventional trailer boom sprayer was selected for comparison.Different spray volumes had a significant effect on defoliation,but had no significant effect on boll opening and fiber quality.A higher defoliation rate was achieved in the lower LAI field.The total rate of defoliation using the UAV was inferior to the boom sprayer in the high LAI field for lower deposition and defoliation rate in the lower canopy.Considering the deposition,defoliation rate,and working efficiency,a spray volume of 15.0 L/hm^(2) with an average droplet size of 150μm is recommended for UAV application.

Evaluation of UAV spraying quality based on 1D-CNN model and wireless multi-sensors system

The droplet deposition is a key index to evaluate the quality of unmanned aerial vehicle(UAV)spraying.The detection of the droplet deposition is time-consuming and costly,therefore,it is difficult to achieve large-scale and rapid acquisition in the field.To solve the above problems,a droplet deposition acquisition system(DDAS)was developed.It was composed of the multiple sensors,processing units,remote server database and Android-based software.A droplet deposition prediction model based on field experimental data was established by using a one-dimensional convolutional neural network(1D-CNN)algorithm,and the effects of different inputs on the prediction ability of the model were analyzed.The results showed that adding temperature and humidity data to the inputs can achieve higher prediction accuracy than only using UAV spraying operation parameters and wind speed data as the inputs to the model.In addition,the prediction accuracy of the 1D-CNN model was the highest when compared with other models such as back propagation neural network,multiple correlation vector machine,and multiple linear regression.The 1D-CNN model was embedded into the DDAS,and the evaluation experiments were carried out in the field.The correlation analysis was conducted between two datasets of the droplet deposition obtained by the DDAS and water sensitive paper(WSP),respectively.The R2 was 0.924,and the RMSE was 0.026μL/cm2.It is proved that the droplet deposition values obtained by the DDAS and WSP have high consistency,and the DDAS developed can provide an auxiliary solution for the intelligent evaluation of UAV spraying quality.

Effects of citrus tree-shape and spraying height of small unmanned aerial vehicle on droplet distribution

In order to explore the droplet penetration of spraying with unmanned aerial vehicle(UAV)on citrus trees with different shapes,the tests were carried out at different working heights.The material was five years old Cocktail grapefruit(Citrus paradisi cv.Cocktail)grafted on Trafoliata(Poncirus trifoliata L.Raf.)and the type of UAV sprayer used was the 3W-LWS-Q60S.A solution of 300 times Ponceau 2R diluents liquid instead of pesticide was used for citrus fields spraying and the droplets were collected by paper cards.Droplets deposition parameters were extracted and analyzed using digital image processing after scanning the cards.The results showed that:1)For the trees with round head shape canopy,the droplet depositions of the upper,middle and lower layers had a significant difference at 0.05 level.The droplet deposition had the best effect when the working height was 1.0 m,where the average droplet deposition densities were 39.97 droplets/cm2 and the average droplet size was 0.30 mm,but the droplet coverage(3.19%)was lower than that at the working height of 1.5 m(4.27%).2)Under three different working heights of UAV,the tree with open center shape can obtain higher droplet deposition density at all three layers than that with the round head shape canopy.It was especially prominent when the working height was 1.0 m,as the middle layer increased by 49.92%.However,the higher range of droplet deposition density meant larger fluctuation and dispersion.3)The open center shape canopy and the 1.0 m working height obviously improved the droplet coverage rate and droplet density in the citrus plant.For these parameters of open center shape citrus tree,there was no obvious difference in the front and rear direction,but in the left and middle part of the tree crown,the difference reached a 0.05 significant level.Considering droplet deposition characteristics and the spray uniformity,the UAV performed better when working on open center shape plants at a 1.0 m working height.

Effects of leaf response velocity on spray deposition with an air-assisted orchard sprayer

The interaction between leaves and airflow has a direct effect on the droplet deposition characteristics of the leaf canopy.In order to make clear the mechanism of droplet deposition in terms of the interaction between the droplets and leaves from the point of the leaf aerodynamic response velocity,the leaf movement under different airflow velocities and the influence of the leaf aerodynamic response on droplet coverage ratio were investigated.The effect of the aerodynamic response velocity of a leaf on the droplet deposition of the leaf surface was investigated.The aerodynamic characteristics of the leaf were analyzed theoretically.Boundary layer theory from fluid mechanics was used to develop a model of the leaf aerodynamic response velocity to nonperiodic excitations based on a convolution integral method.Target leaf aerodynamic velocities were detected using a high-speed camera,and the results indicated that the modeled leaf aerodynamic response velocity matched the measured values.At given conditions of spray liquid and leaf surface texture,the spray test showed that the droplet coverage ratio was influenced by the leaf aerodynamic response velocity,the droplet coverage ratio increased and then decreased with the leaf response velocity.Through analyze four droplets deposition state,the highest droplet deposition ratio and best deposition state on the leaf surface occur when the leaf aerodynamic response velocity was less than 0.14 m/s.According to the analysis of droplet deposition states,the uniformity of the droplet size and quantity distribution of droplets on the leaf surface related to the leaf aerodynamic response velocity.The results can provide a basis for the design and optimization of orchard air sprayers.

Feedback regulation system for spraying parameters based on online droplet mass deposit measurements

In order to effectively optimize and regulate spraying parameters based on actual spraying performance and improve pesticide utilization rate,in this research,a feedback regulation system for the regulation of spraying parameters was designed based on droplet mass deposit online measurement.The system consisted of an online droplet mass deposit measurement module,wireless transmission module,decision module,and spraying parameters regulation module.First,the droplet mass deposits on the sampling points were measured.Based on the deviation between the measured and expected droplet mass,the expected spraying parameters were determined by the decision module.The spraying parameter was regulated to the expected value by regulating the pulse duty cycle on the pump motor using a micro control unit and a relay.Evaluation tests were conducted indoors using an indoor spraying platform and outdoors using an unmanned aerial vehicle.The results showed that the relative errors between the expected and measured droplet mass deposit after regulation were 6.84%and 11.48%for the indoor and outdoor tests,respectively.Therefore,an optimal spraying performance was observed after regulation.This research provided an experimental platform to quickly optimize spraying parameters and also provided technical references for precision spraying.

Adaptive spraying decision system for plant protection unmanned aerial vehicle based on reinforcement learning

To solve the problem of lacking scientific guidance in aerial pesticide application,this study introduced an adaptive spraying decision system(ASDS)for Unmanned Aerial Vehicle(UAV)spraying to guide the operators of plant protection UAVs to set reasonable spraying parameters under complicated environment.The minimum applied volume rate,proper spraying velocity,spraying height,and initial droplet size were recommended by the ASDS.The key factor of the decision system is the decision model of reinforcement learning based on the actor-critic neural network.In specific,the field experimental data were used to train the critic and actor networks,which made the model adaptive to optimize the output of spraying parameters.Compared with the conventional spraying parameters,the spraying parameters recommended by the ASDS had a positive impact on wheat parcels.The decision results of the ASDS showed that the spraying volume rate was lower in the blocks with a small leaf area index.In addition,the spraying volume rate for the whole parcel was reduced by 14%.After UAV spraying,the uniformity of the droplet deposition in the ASDS parcel was better than that in the conventional parcel.Moreover,the penetrability of the droplets and the control efficacy for the brown wheat mite Petrobia latens(Muller)were similar in the two parcels.The ASDS can recommend the optimal spraying parameters to minimize pesticide application.

Numerical study of particle motion near a charged collector

The behavior of particles impacting the surface of a charged droplet involves adhesion, rebound, and submersion. In the present study, a numerical model for simulating particle impacts on charged droplets is presented that takes into account the various impact modes. With the droplet considered as a solid boundary, the criterion for rebounding is that the particle＇s impact angle is 〈85°. The simulated trajecto- ries of the particles are verified by comparing with experimental data for low-velocity particles to assess the reliability of the model. For impact angles 〉85°, particles undergo three distinct modes depending on normal impact velocities. The critical velocity of adhesion/rebound and rebound/submersion is used to identify the mode that the particles are undergoing. The criteria are also verified by comparing with ana- lytical data. The results show that the impact angle of particles increases with increasing Coulomb number and decreases dramatically with increasing Stokes number, both of which lead to a high probability for particle rebound.