Spray Drift Measurement Technology And System Development Based On LiDAR Point Cloud

The use of pesticides is of great significance to the prevention and control of pests and weeds and to ensure food security.In the process of pesticide spraying,spray drift is inevitable due to the influence of environmental wind,auxiliary airflow of spraying equipment and operating parameters.The measurement of pesticide drift can provide data support for the development of pesticide application equipment,which is of great significance for the prevention of secondary disasters and the performance evaluation of pesticide application equipment.At present,spray drift is mainly obtained by arranging a large number of samples in the field to obtain the distribution of droplets drift,which is time-consuming and laborious,with high experimental cost and long measurement period.In this paper,the measurement technology of spray drift based on LiDAR point cloud data is studied,the measurement model of spray drift based on LiDAR point cloud data is constructed,and the measurement system of spray drift is developed.The drift amount and spatial distribution are inverted by non-contact LiDAR detection point cloud.The main research contents and results are as follows:（1）A spray drift measurement model based on LiDAR point cloud data is constructed.Spray experiments are carried out in a wind tunnel with precise and controllable environmental conditions.The effects of droplet size and spatial drift droplet density on LiDAR detection of spray droplets are analyzed.The optimal droplet size and spatial drift droplet density for LiDAR detection of spray droplets are determined to be 200-250μm and50-100 pcs cm^-2,respectively.Using BP neural network algorithm,a spray droplet drift measurement model based on LiDAR point cloud data is constructed.The determination coefficient R²of the test set is 0.88,the similarity coefficientis 0.94,and the mean absolute percentage error MAPE is 29%,which provides model support for spray droplet drift measurement.（2）A spray drift measurement system is developed.The mechanical structure and control circuit of LiDAR online measurement platform are designed.The measurement system software is developed by using C++language and QT application development framework.The stability and accuracy of the system are tested.The test results show that compared with the polyethylene line tracer elution measurement method,the positive and negative error kurtosis values of the system drift measurement are negative and close to 0,the R²of regression results between measured values of the system and the polyethylene line collection drift is 0.88,theis 0.94,and the MAPE is 30%.（3）The application test experiment of plant protection UAV field spray system are carried out.The field spray experiment of plant protection UAV is carried out.The drift measurement system and polyethylene line tracer elution measurement method are used to measure the drift and spatial distribution of downwind spray droplets,and the applicability of the system in the field operating environment is evaluated.The experimental results show that the positive and negative error kurtosis values of the system drift measurement are negative and close to 0,and the R²of the fitting results with the elution measurements of polyethylene line is 0.79,theis 0.89,and the MAPE is 69%.The system realizes the online rapid measurement of spray drift of plant protection UAV in the field.The spatial distribution map of drift can be obtained by inversion of point cloud data,and the distribution range of drift droplets can be calculated,which provides data support for the setting of pesticide application buffer zone,flight parameter optimization and spraying equipment development of plant protection UAV.