Research And Experiment Of Velocity Adaptive Variable Pesticide Application System For UAV

In recent years,with the continuous development of aviation plant protection technology in China,the requirement for precise application of pesticides is getting higher and higher.However,there are still some problems in China,such as the uneven deposition and droplet size caused by the fluctuation of UAV speed.Aiming at the above problems,based on the analysis and summary of the technology achievements of variable rate pesticide application at home and abroad,this paper focuses on the speed acquisition method of UAV,the flow rate of pesticide application and the control mode of spraying droplet size,establishes the relationship model between flow rate and flow rate,and analyses the relationship between droplet size and flow rate,centrifugal nozzle speed.By controlling the input voltage and separation of diaphragm pump.The rotational speed of the nozzle improves the uneven deposition and droplet size,which provides a strong support for UAV variable rate pesticide application technology.The main work and conclusions of this paper are as follows:?1?UAV speed data acquisition and processing.Taking the plant protection unmanned helicopter as the research object,by analyzing the GPS fixed on the fuselage,the flight speed and its change of the unmanned helicopter were collected.The transmission rate of GPS is 5Hz,and the transmission protocol is UBX.The data information is sent to STM32F103VET6 chip in real time through TTL serial port,and the speed information is extracted by central processing unit.Experiments show that the UAV's speed will rise,fall and fluctuate continuously in the process of operation.The UAV's speed collected in the experiment will change continuously at 200 ms speed,and the maximum fluctuation range is 8 m/s.It provides data support for the design and development of UAV variable rate pesticide application system and theoretical basis for system performance verification.?2?Development and test of flow control module.Aiming at the uneven distribution of droplet deposition caused by the change of UAV flying speed,a method of adjusting the nozzle flow rate adapt by velocity was proposed and studied,and a model of the relationship between spraying amount and flying speed was established.The system converts the flight speed of UAV acquired in real time into expected flow data,and converts the difference between expected flow and real-time flow into PWM signal to control the input voltage of diaphragm pump combined with the preset PID algorithm.A velocity adaptive flow control model is established,and the main performance of the flow control module is tested through indoor and field experiments.The results show that the control delay of the module is less than 100 ms,and the average control delay is 500 ms when the flow changes continuously.In the field operation test,the uneven application of pesticides has been improved to a certain extent,and the uniformity of surface sediment can be increased by 30.47%.?3?Development and test of droplet size control module.In order to solve the problem of non-uniform droplet size caused by the change of flow rate in the application process of plant protection UAV.The droplet size control module based on centrifugal nozzle is proposed and developed in this system.The centrifugal sprinkler can adjust the rotational speed of the sprinkler according to the real-time change of flow rate to ensure that the size of spray droplets remains unchanged.The mathematical model between flow rate,nozzle speed and droplet size was established in laboratory experiments,and the performance of droplet size control module was tested in laboratory and field experiments.The experimental results show that the droplet size is negatively correlated with the rotational speed of centrifugal nozzle and positively correlated with the flow rate of nozzle.After the variable spraying system was opened,the Dv₅₀ of droplet size was closer to the optimal value of 250?m,and the average value of the closest droplet size was 245.97?m.Therefore,the variable-rate spraying system can improve the droplet size change caused by the change of flow rate.