Continuous control of a sprayer pinch valve.

An air pinch valve was modified to be continuously variable by the addition of a rigid insert and continuous air pressure regulation. A technique for state-space modeling of the valve’s dynamic performance was developed. State feedback control based upon pole placement was unstable due to unmodelled nonlinearities. Experiments indicated that integral closed-loop control produced satisfactory transient and steady-state responses for individual nozzle control. Such valves might be utilized in the spatially variable control of fertilizer or pesticide application common in precision agriculture.