The Design Of PWM Variable Sprayer And The Study Of Its Pressure Characteristics

The situation of pesticide application in existing farmland orchards in China is relatively complex,and the demand for medicines varies greatly between regions.Normal spraying and plant protection machinery cannot be accurately and intelligently operated,so variable application technology has become an important issue for the future development of plant protection.direction.In the variable spray method,the variable flow application system is universally approved,that is,by connecting a high-speed on-off solenoid valve in the front line of each spray unit,and by changing the ratio of the on-off time of the electromagnetic valve.To achieve a change in the average spray rate of the spray head.However,because it increases the form of the electromagnetic valve and the nozzle,it causes pressure fluctuations.However,the pressure fluctuation will have a great impact on the distribution of fog,spray stability and other characteristics,so it is very important to study the pressure stability in the variable spray.The significance.In this paper,the PWM signal is used as the variable control method,and the existing computer experimental platform is used to test and analyze the pressure fluctuations,and the best combination of the electromagnetic valve and the nozzle is obtained.At the same time,the operation process state detection and variable control requirements of the spray process are used,and independent development is performed.A set of variable controllers and control panels were designed and manufactured.The specific work and results of this paper are as follows:1.Based on the 12-meter boom sprayer,configure the corresponding sensors,solenoid valves,control units and other monitoring and control components,using the PWM pulse signal as a control method to build a complete set of variable application system.Field tests show that the variables are effective.2.Researches and experiments were conducted on the influence of the solenoid valve diameter and spray flow rate on the spray pressure fluctuation characteristics.The test and test results show that under the condition that the pressure at the outlet of the constant pressure device is stable and the flow rate does not change,the diameter of the solenoid valve increases,the mean value of the pressure also increases,and the dispersion rate of the pressure fluctuation decreases,and the diameter decreases.The mean pressure also decreases,and the dispersion of pressure fluctuations increases.When the pressure at the outlet of the constant pressure device is stable and the diameter of the solenoid valve does not change,the flow rate increases,and the average pressure decreases.With a diameter of DN15 and DN10,the flow rate increases,and the dispersion rate of pressure fluctuation does not change significantly.Below 0.002 and 0.01,respectively,and with a diameter of DN6,the flow increases,and the dispersion of pressure fluctuations rises faster,but it remains below 0.03.According to the test,the combination of electromagnetic valve and nozzle in the design of this paper is obtained.3.According to the requirements of the PWM system studied in this paper,complete the circuit design and manufacture of the PWM controller and control panel,and write the corresponding module program through software.According to the actual test,the variable spraying controller and the control panel can communicate well and realize the detection of the variable spraying operation status and the rapid adjustment of the flow rate.4.Through testing the change of the mean value of spray pressure during the abrupt change of flow rate,the test results of the overflow device and the flow control model are verified.The mean value of the pressure tends to be stable in the early stage of the test,and abrupt fluctuations occur when the number of sprinklers is reduced by half.As the overflow device works,the mean pressure becomes stable in a short time.