Design and performance test of electronic control precision nozzle body based on PWM

Abstract: Aiming at the problems of low precision of variable spray in the existing farmland pesticide application system and the inability of independent control of the nozzle, an electronic control precision nozzle body with a flow adjustment function was designed. According to the working requirements of the precision spray system, based on the electromagnetic theory, an electromagnetic pull-in mechanism composed of a solenoid coil, a fixed iron core, a spool and a return spring was designed to realize the high-frequency reciprocating motion of the valve core. Combined with the structure of the water flow channel of the nozzle body and the reciprocating movement process of the valve core, the end type of the spool and the two-way water flow valve were designed to realize the on-off control of the water flow. The Pulse Width Modulation (PWM) signal was used to control the action state of the electromagnetic pull-in mechanism, change the opening time of the water outlet channel in each cycle, and realize the real-time adjustment of the nozzle flow. By setting different pulse width modulation signal frequency and duty ratio, water pump pressure, and using a high-speed camera to measure the spray time of the electronically controlled precision nozzle body in a single cycle under different pressures, the working performances of the designed electronically controlled precision nozzle body were verified. The test results showed that when the pulse width modulation signal frequency was 20 Hz and the system pressure was 0.3 MPa, the minimum duty cycle that the valve core could open was 7%, and the maximum duty cycle that the valve core could close was 96%; the average relative error of spray time in a single cycle was 7.5% and the maximum relative error was 55.1% at the duty cycle of 7%, 96%; the average relative error of spray time in a single cycle was 3.1% and the maximum relative error was 13.1% at the duty cycle of 20%, 96%. It showed that the control effects of the electronic precision nozzle body were poor at the duty cycle of 7%, 19%, and had good control stability and accuracy at the duty cycle of 20%, 96%.