Ground Speed Control of Pesticide Application Rates in a Compressed Air Direct Injection Sprayer

Abstract

This article describes a technique to control pesticide application rates in direct proportion to varying ground speed for a compressed air direct injection (CADI) sprayer. The CADI sprayer was a closed loop sprayer in which the liquids were delivered by applying air pressure in the liquid reservoirs. A radar sensor and an oval gear flow meter gave output signals proportional to ground speed and pesticide flow rate, respectively. These outputs were used as inputs to a datalogger unit to compute a difference between the desired and actual flow rates. The datalogger unit activated a stepping motor attached to a pressure regulator of the sprayer to adjust liquid-reservoir air pressure for obtaining the desired flow rate. The laboratory and field testing of this unit indicated that the desired flow rate of a simulated pesticide was achieved within reasonable cycles of the control program without system oscillation.