Abstract:In order to study the application rate control characteristics of blended pulse variable rate application system, a blended pulse variable rate application system was constructed based on a commercial boom sprayer and by integration of high speed direct acting solenoid valves (type 6013), hollow cone nozzles (type TR80-05), pilot-operated proportional relief valve (type DBEE6-1X/50) and a self-designed PWM-based variable rate application controller. Influences of diaphragm pump’s input shaft rotating speed, nozzle positions, spray pressure, PWM signal frequency and duty cycle on nozzle’s spray flow rate were tested. Computational models of the nozzle’s spray flow rate under spray pressure of 0.2 MPa, 0.3 MPa and 0.4 MPa were fitted through monothetic linear regression, and corresponding control models of application rate were deduced. Application rate control characteristics testing experimentation of the blended pulse variable rate application system was performed too. Test results show that influences of nozzle positions and PWM signal frequency on the nozzle’s spray flow rate are very little, spray pressure and PWM signal duty cycle have crucial influences on the nozzle’s spray flow rate, the ratio of flow regulation is about 10∶1 with combine of the solenoid valve and the nozzle used in the system, the control error of spray flow rate is less than ±4% when objective spray flow rate is greater than 0.3 L/min, and the control error of application rate is less than ±6%.