Analysis of and H∞ controller design for an electro-hydraulic servo pressure regulator

Currently mobile hydraulics is in a transition phase, where electronic sensors and digital signal processors are becoming standard on a high number of machines, hereby replacing hydraulic pilot lines and offering new possibilities with regard to both control and feasibility. As most open-circuit pumps are still hydraulically controlled, there is however still a need for being able to generate a hydraulic pilot pressure. The focus of the current paper is on the analysis and controller design of an electro-hydraulic servo pressure regulator, which generates a hydraulic LS-pressure for a variable displacement pump based on an electrical reference. The paper first presents the considered system and an experimentally verified model of this. A linearized model and a stability analysis is then presented, based on which an H_∞ control strategy is selected. A nominal performance and a robustly stable controller are designed and tested in simulation and experimentally. Finally both controllers are compared to the reference system, finding that similar performance may be obtained, but the used FPGA limits the performance.