Improving the Response of an Electrohydrostatic Actuation (EHA) System Using a High-Pressure Accumulator

In this paper, we propose a novel hydraulic actuation system driven in three modes to improve the response of the existing electrohydrostatic actuation (EHA) system. By using a high-pressure accumulator, a servo valve, and mode switching valves, the hydraulic circuit can be switched to suit each mode according to the operational conditions. Each of the three modes consists of the EHA mode, the hybrid mode, and the charge mode, and the EHA mode operates on the same principle as the existing EHA system. Particularly, the hybrid mode is activated when high-speed position control is required, and with the help of an add-on servo valve controller, the control volume of the hydraulic cylinder can be stiffened quickly while minimizing the use of highly pressurized fluid. The charge mode serves to periodically charge the accumulator under motionless conditions in applications that allow piston holding. Through simulations and experiments, it was confirmed that the response of the proposed system is much improved compared to that of the existing EHA system.