The Research On Key Techniques Of Spraying Machine For Target Variables In Mountain Orchard

Pest control in orchards has always been the most arduous part of orchard management.At present,most methods of pest control in orchards mainly rely on chemical control.There are large differences in the planting patterns of orchards in various regions of China,and there are problems of excessive application of pesticides during spraying operations,which poses a serious threat to food safety and the environment.Aiming at the above problems,in this paper,an all-electric profile variable application sprayer was designed based on the planting pattern of southern citrus orchard in China,which was used to improve the utilization rate of pesticides to prevent pests and diseases,and to reduce pesticide residues and environmental pollution.The main contents of this paper include:(1)According to the planting mode of the southern citrus,the overall design of the air-to-target sprayer was determined.Based on the different growth stages of fruit trees,a profiled spray bar was designed.The spray bar can adjust the spray height and angle according to the height of the fruit tree to achieve the purpose of the profile spray.The static simulation of the overall boom structure is carried out.The simulation results show that the maximum stress is much smaller than the yield strength of the material,and the strength check meets the requirements.(2)The sprayer performs fan test experiments on different duty cycles in a windless environment.The test results show that the wind speed,wind pressure and air flow increase linearly with the increase of the duty cycle of the input PWM wave signal.The maximum values are 11.761 m/s,80 Pa,1045 m~3/h,which can fully meet the requirements of the general orchard air spray system,and establish a wind speed,wind pressure and air flow model based on PWM wave control.A test bench based on the PWM variable spray nozzle flow model was designed.The relationship between nozzle flow and nozzle pressure,solenoid valve frequency,and frequency duty cycle was determined experimentally.The test shows that the spray pressure is 0.4 MPa,and the frequency of the solenoid valve is 5 Hz.The spray model has the best linear relationship and the spray uniformity is the best.(3)A target detection system is designed,which collects the distance point cloud of the object by laser radar,and detects the speed and distance of the lidar movement in real time through a rotary encoder.Each collected point cloud and the corresponding rotary encoder pulse are matched to form a three-dimensional space coordinate.Data acquisition and model reconstruction are performed on regular objects and irregular crowns.After the model is tilt corrected,the quantitative analysis results show that:The relative errors of the length,width and depth of the regular object measured by lidar are 6.36%,1.21%and 6.19%;Data collection and reconstruction of the fruit tree canopy can restore the contour model of the fruit tree canopy more clearly.For the quantitative analysis of the contour model,the relative errors of the maximum height and the maximum width of the crown are 8.67%and 10%.Finally,according to the number and size of the boom,the depth image of the fruit tree is meshed.In order to improve the accuracy,sub-grids are divided in each grid,and the sub-grid volumes of the fruit trees in each grid are added to obtain the volume of the target fruit tree corresponding to each boom unit.The calculated target volume is calculated to obtain the volume of the entire fruit tree.The test shows that the laser radar has a volume of about330,045,210 mm~3 in the range of 1.5～2 m from the target fruit tree,and the relative error with the manual measurement is only 10.78%.The fruit tree target model is combined with the spray model based on PWM wave control to establish the relationship between fruit tree volume,PWM wave duty ratio and vehicle speed,which provides a basis for applying target variables.