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.

Evaluating effective swath width and droplet distribution of aerial spraying systems on M-18B and Thrush 510G airplanes

Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G,the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m.The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s,and the directions of the atomizer switched upward and downward in eight flights,the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G,respectively,and the latter was more stable.In addition,through analyzing the coefficients of variation(CVs)of droplet distribution,it was found that the CVs of the M-18B were 39.57%,33.54%,47.95%,and 59.04% at wind velocities of 0.9,1.1,1.4 and 4.6 m/s,respectively,gradually enhancing with the increasing of wind speed;the CVs of Thrush 510G were 79.12%,46.19%,14.90%,and 48.69% at wind velocities of 1.3,2.3,3.0 and 3.4 m/s,respectively,which displayed the irregularity maybe due to change of instantaneous wind direction.Moreover,in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath,choosing smaller CV(20%-45%)as the standard of estimation,it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B.The results provide a research foundation for promoting the development of aerial spraying in China.

Effect of aerial spray adjuvant applying on the efficiency of small unmanned aerial vehicle for wheat aphids control

Small unmanned aerial vehicles(UAVs)have been widely used in different aspects of modern farming management,including pest and disease control in China in recent years.In this study,the spray performance of a small plant protection UAV at low volume spray was evaluated by adjusting the pesticide dosage and adding aerial spraying adjuvants.Droplet deposition,droplet density,coverage,control effect and pesticide residue from field trials were assessed.In addition,the residue and control effect of UAV spray were compared to manual knapsack at high volume spray.The results showed that,the adjuvant applying improved the efficiency of UAV spray.Also,the adjuvant applying reduced the dosage of imidacloprid by 20%.However,there was no significant difference on initial residue between UAV spray and knapsack spray.Thus,plant protection UAV spraying pesticide by adding appropriate adjuvant showed the ability of improving the pesticide effectiveness by improving the control efficiency,reducing the pesticide dosage and residue.

Optimization of variables for maximizing efficacy and efficiency in aerial spray application to cotton using unmanned aerial systems

Aerial spraying can support efficient defoliation without crop contact.With the recent introduction to unmanned aerial system(UAS)for aerial spraying in China,there is a need to determine the optimum application variables to achieve high efficacy and efficiency with low costs.The present research involved field studies across two annual cotton production seasons in North Xinjiang,China.Four factors,including volume rate(A),tank mix including spray adjuvants(B),flight altitude(C),flight speed(D)and three levels of L9(3^(4))orthogonal arrays were carried out to optimize the application parameters for three types of UASs.These included different numbers of rotors as follows:four-rotors,six-rotors and eight-rotors.Spray coverage,distribution uniformity(coefficient of variation(CV)of droplet coverage),rates of cotton defoliation and boll opening,application efficiency and cost were measured and assessed.Results showed that:(1)the rates of defoliation and boll opening by aerial cotton defoliant application could meet the requirement of cotton mechanized harvesting;(2)the optimal scenario for the three UASs was A_(3)B_(2)C_(1)D_(3),Volume rate(A3):48 L/hm^(2);Tank mix and concentration(B_(2)):(Tuotulong 225+Sujie 750+Ethephon 2250)mL/hm^(2),Flight altitude(C_(1)):1.5 m,and Flight speeds(D_(3))for unmanned helicopters with four-rotors,six-rotors and eight-rotors were 3.12 m/s,2.51 m/s and 3.76 m/s,respectively.These results can provide guidance for cotton defoliant aerial spraying in China using UAS.

Current status and future trends of precision agricultural aviation technologies

Modern technologies and information tools can be used to maximize agricultural aviation productivity allowing for precision application of agrochemical products.This paper reviews and summarizes the state-of-the-art in precision agricultural aviation technology highlighting remote sensing,aerial spraying and ground verification technologies.Further,the authors forecast the future of precision agricultural aviation technology with key development directions in precision agricultural aviation technologies,such as real-time image processing,variable-rate spraying,multi-sensor data fusion and RTK differential positioning,and other supporting technologies for UAV-based aerial spraying.This review is expected to provide references for peers by summarizing the history and achievements,and encourage further development of precision agricultural aviation technologies.

Development of a low-cost quadrotor UAV based on ADRC for agricultural remote sensing

Unmanned aerial vehicle(UAV)has the advantages of good repeatability and high remote sensing(RS)information acquisition efficiency,as an important supplement bridging the gap of high-altitude and ground RS platforms.A quadrotor UAV was developed for the agricultural RS application in this study.The control system consists of a main processor and a coprocessor,integrating a three-axis gyroscope,a three-axis accelerometer,an air pressure sensor and a global positioning system(GPS)module.Engineering trial method(ETM)was used to tune the parameters based on the active disturbance rejection control(ADRC)method.Also a ground control station(GCS)adapted to the quadrotor was developed realizing autonomously take-off and landing,flight route planning,data recording.To investigate the performances of the UAV,several flight tests were carried out.The test results showed that the pitch angle control accuracy error was less than 4°,the flight height control accuracy error was less than 0.86 m,the flight path control accuracy error was less than 1.5 m overall.Aerial multispectral images were acquired and processed.The reflected digital number(DN)values obtained from a height of 10-100 m with 10 m interval could be referenced to classify objects.The normalized-difference-vegetation index(NDVI)values obtained from the aerial multispectral images acquired at 15 m were compared with those obtained by the GreenSeeker(GS)and PSR-1100F.The maximum error was 20.37%while the minimum error was 1.99%,which demonstrated the developed quadrotor UAV’s satisfactions for low altitude remote sensing practice.This study provided a low-cost platform for agricultural remote sensing.

Optimization of control parameters of droplet density in citrus trees using UAVs and the Taguchi method

The control parameters of the unmanned aerial vehicle(UAV)should be carefully designed to improve UAV spraying performance on citrus trees.The present study investigated the optimal droplet distribution control parameters in citrus trees using a UAV and the Taguchi method,of which optimal results were observed with an inverted triangle citrus tree canopy shape,a spraying height of 1.40 m,and a flight speed of 1.0 m/s.Among the discussed control parameters,the flight speed presented the most significant effect with a contribution percentage of 74.0%.The established multiple regression model predicted an optimal spraying height of 1.27 m and a maximum droplet density of 35.39 droplets/cm2.In addition,the effects of individual control parameter on the droplet density of the lower layer of citrus trees were systematically analyzed,of which inverted triangle shape more significantly affected the droplet density of the lower layer and presented an 82.0%increase in droplet density as compared to the triangle shape.An improvement of 59.6%in the lower layer droplet density was observed at a spraying height of 1.40 m.In addition,the other spraying heights did not present significant differences in their coefficient of variation(CV)values.

Design and experiment of a hydraulic lifting wind field test platform for crop protection UAS

As a new type of crop protection machine,the crop protection unmanned aerial system(CPUAS)is developing rapidly in China.The wind field generated by the rotor has a great influence on the deposition and penetration of spraying droplets.The purpose of this study was to develop a reliable and stable test platform that could be used for wind field test of CPUAS,and to carry out the downwash experiments on the platform to obtain the downwash distribution law of a CPUAS Z-3N(100 kg level,Nanjing Research Institute on Simulation Technique,Nanjing,China).The tests showed that the performances of the developed platform could meet the expected design requirements.The platform operated stably and reliably during the downwash experiments of Z-3N,which indicated it could be applied for CPUASs of 100 kg level and below.The vibration characteristics of the platform with different heights(2.0 m,3.0 m,5.0 m,7.0 m,10.0 m)were obtained through modal analysis,which could effectively guide avoiding the resonance for stable and reliable operation during the experiments with the tested CPUAS Z-3N.A ring-radial method was designed combined with the platform for the downwash measurement.The experimental results showed that the downwash distribution of Z-3N was not symmetrical;the downwash wind speed decreased with the increase of the radial distance while the changing trend was not consistent as the height increased.Moreover,the area with high wind speed was mainly within 3.0 m of the radial distance,and the maximum value was 11.37 m/s.The study provided a new way for wind field test of CPUASs and would provide some references for better utilization of wind field during the CPUAS spraying.