Research On Variable-rate Spray Control System Of Crawler-type Orchard Sprayer

Spray control is the main way to prevent and control insect pests in forest and fruit industry.The traditional sprayer generally adopts the continuous spraying method of heavy fog,which not only wastes pesticide but also pollutes the environment.And,it is harmful to the health of farmers.In order to reduce the labor intensity of farmers and achieve the goal of reducing pesticide and increasing efficiency,in this study the control system of crawler-type orchard sprayer was studied;the flow controller of solenoid valve based on BOOST circuit was designed;the model of circular variable drug application was established;a precise variable spray control system was designed.The main research contents are as follows:(1)Aiming at complex terrain and harsh working environment of orchard,walking control system of remote crawler sprayer with better performance was designed.In order to improve the operation comfort and reduce the contact between liquid medicine and operators,a remote control system was designed to realize the separation of human and machine.The structure of sprayer was designed by SolidWorks software,and the spatial distribution of electromagnetic nozzles was optimized.A remote precision variable sprayer control system was built up by laser sensor,embedded computer,variable flow control,encoding speed measurement,wireless communication and STM32F4 main controller.(2)In order to improve the linear range of solenoid valve output flow,a solenoid valve flow controller based on BOOST circuit was designed.BOOST circuit and drive circuit of solenoid valve was combined by using inductance characteristic of solenoid valve.Through the double voltage driving strategy,the solenoid valve can be accelerated to open at high voltage,maintained on at low voltage and high frequency,and quickly released to close.The results showed that under the pressure of 110,250 and 390 kPa,the flow linear range of the improved flow controller was increased from 10% ~ 92%,10% ~ 92%,8% ~ 92% to 4% ~ 92%,4% ~ 94%,3% ~ 94%,respectively,and the improved flow controller had wider linear range of flow.(3)Aiming at the annular spray structure,an annular target spraying model was put forward.Compared with the vertical spray mechanism on both sides,the annular spray structure was smaller and the spray range was larger,so as to meet the special spray needs of grape and other dense planting orchard.Firstly,the annular distribution solenoid valve spray unit matched with the sprayer was designed,and the spray sector was divided according to the spatial distribution of the nozzle.An annular structure spraying model was put forward to calculate the required spray amount according to the volume of the canopy.The main cause of spray delay was analyzed,and a time delay compensation algorithm was used.Finally,the experimental results showed that the spray delay compensation algorithm can match the target characteristics in real time and achieve accurate target variable spray.(4)In order to improve the utilization rate of liquid medicine and reduce environmental pollution,a precise variable spray control system was designed.Laser sensor was used to scan target characteristic information in real time,and the 3D model of plant target was constructed combined with the forward speed of sprayer.A precision variable spray experiment was designed.The results showed that the output volume of the sprayer matches the volume of the canopy,and the pesticide consumption was reduced on the basis of satisfying the pest control requirements in the orchard.