Development of an integrated actuator for real time control of spray nozzle flow rate and droplet size spectrum

Application of agrochemicals is essential to U.S. production of food, fiber, biofuels and ornamentals. However, it can also create environmental contamination if pesticides reach non-target areas through airborne displacement of spray, i.e., "spray drift". Drift is a concern for agriculture, especially for specialty crops grown in sensitive areas. Spray drift mitigation, through use of larger droplets, unsprayed buffer zones and slower ground speeds can conflict with efficient, economic crop production. Concurrently, precision pesticide application using GPS, sensors, etc., is growing; yet spray actuators can be the limiting factor in spatial resolution. This project will develop a single, at-nozzle actuator to control the application rate and spray droplet size at the spatial resolution of a single nozzle, allowing highly precise variable rate application and drift control. This will also allow buffer zones to be highly resolved and drift control to be electronically verified. The approach will be to develop a high-speed pulse width modulated (PWM) valve that can be partially opened during each pulse cycle. The duty cycle of pulses will control the flow rate while the modulated opening will control the pressure drop across the valve and correspondingly, the spray droplet size from the attached nozzle. This is a significant advance in spraying capability; yet, it will leverage the existing market acceptance of PWM spray rate control.