Controlling a Conventional LS-pump based on Electrically Measured LS-pressure

As a result of the increasing use of sensors in mobile hydraulic equipment, the need for hydraulic pilot lines is decreasing, being replaced by electrical wiring and electrically controllable components. For controlling some of the existing hydraulic components there are, however, still a need for being able to generate a hydraulic pilot pressure. In this paper controlling a hydraulic variable pump is considered. The LS-pressure is measured electrically and the hydraulic pilot pressure is generated using a small spool valve. From a control point of view there are two approaches for controlling this system, by either generating a copy of the LS-pressure, the LS-pressure being the output, or letting the output be the pump pressure. The focus of the current paper is on the controller design based on the first approach. Specifically a controlled leakage flow is used to avoid the need for a switching control structure.