Abstract: A control system for transferring fluid between a fluid supply and a process. The control system includes a transfer controller, which outputs a transfer signal that corresponds to a time varying fluid transfer rate, and plural valves that are plumbed in parallel for connection between the fluid supply and the process. Each valve has a corresponding input to receive an actuation signal that enables a closed state or an open state. The system also includes plural means for limiting the rate of fluid flow corresponding to the plural valves, and a valve drive that is coupled to the corresponding inputs of the plural valves, which operates to generate a sequences of valve actuation signals that result in a combined fluid flow rate through the plural valves selected to track the time varying fluid transfer rate defined by a modulated transfer signal within a margin of error.

Abstract: An airborne container for a liquid or other flowable material has bottom doors which are opened to release the material on the ground below the aircraft. To maintain a specified coverage level, a control system which includes a digital controller repeatedly calculates a differential pressure across the doors and varies the position of the doors to maintain a constant material flow rate as the differential pressure varies. The control system closes the doors when a specified volume of material has been spread.