Nhila, A. and Williams, D., "Control of Pressure Build-up inside a Power Steering Gear through Active Flow Control without Throttling," SAE Technical Paper 2015-01-2725, 2015, doi:10.4271/2015-01-2725.
Today's hydraulic steering systems suffer from poor efficiency due to their use of throttling valves to build pressure inside the steering gear. In this work, we propose a novel way to build and control pressure by controlling the flow from the pump and without throttling. As a result, such a system will be more energy efficient. Moreover, the ability to control pressure inside a steering gear, and thus assistance torque, allows the steering system to become an active closed-loop system rather than a passive open-loop system. Specifically, by controlling pressure, one can closely control the hand wheel torque the operator feels. Consequently, the new pressure control concept has the potential to not only significantly improve the efficiency of steering systems, but also offers the numerous benefits of torque overlay without the use of an electric motor. Such benefits include the possibility of doing closed-loop hand wheel torque control, autonomous steering, lane keeping assistance, stability control with steering, etc.