Abstract: A rotory servovalve is constructed with a cylindrical annular housing and a cylindrical valve element rotatable therewithin. The valve housing has at least two inlet orifices, at least two outlet orifices, at least two first fluid transfer control orifices, and at least two second fluid transfer control orifices. At least two orifices of each type are located on opposite sides of the valve housing from each other. Preferably there is a first end orifice, a central orifice, and a second end orifice of each type. The end orifices of each type are angularly and longitudinally aligned with each other and are angularly offset 180 degrees from a central orifice of the same type. The end orifices of each type have an area equal to one-half the area of the central orifice of the same type and are equally spaced in opposite longitudinal directions from the central orifice of the same type.

Abstract: A control valve or system of control valves governs fluid flow by digitally comparing a feedback signal from a fluid control loop with a command signal corresponding to a desired flow rate in a high pressure operating fluid flow line. In the preferred embodiment, a control valve system, such as a pressure relief valve, is operated under the control of a digital computer. The pressure relief valve is operated at a control pressure to regulate flow in an operating hydraulic system. The control pressure chamber is coupled to a relief line through a control pressure reduction valve and to a control pressure enhancement valve which is in communication with the operating line of fluid flow. A feedback signal indicating actual control pressure, flow rate or load position is compared with a command control pressure, flow rate or position. Preferably, the results of several comparisons are averaged together to provide an error correction signal.

Abstract: A pulse width modulated control signal is applied to inlet and outlet solenoid valves in a closed fluid vehicle brake system. The electronic actuating circuitry can control a fluid brake system in a towed vehicle from a towing vehicle without fluid connections therebetween. The closed fluid brake system provides an electrical feedback signal that tracks an electrical command signal applied by the towing vehicle operator through a manually operated command signal transducer to produce an error signal to maintain a command pressure in the towed vehicle fluid brake system. The inlet and outlet valves are repeatedly opened and closed in accordance with the width of a train of pulses. The pulse width is proportional to the difference between an electrical command signal and an error signal.