Thomas, A., "Development of the Bishop ATS Rotary Valve," SAE Technical Paper 970380, 1997, doi:10.4271/970380.
A hydraulic rotary power steering valve has been developed that allows low noise levels to be achieved without the need for extreme accuracy on the metering edges of the input shaft. The valve strategically utilises back pressure to reduce the cavitation noise normally associated with power steering valves. The back pressure is applied in a way that does not result in a sacrificial energy loss. This new valve design also permits a linear valve characteristic to be achieved, previously unobtainable via conventional input shaft grinding methods.