A Dual-Pump Energy-Efficient Electro-Hydraulic Drive with Extended Velocity Range

This paper addresses some challenges of expanding the velocity range of energy-efficient, electro-hydraulic actuators to enable low-velocity operations for extended periods of time. Our main research question is how to avoid low-speed functioning of the hydraulic pumps while maintaining a simple and cost-effective system design. We propose a dual- pump drive equipped with a mechanical-hydraulic switching valve that smoothly disconnects one pump from the hydraulic actuator when low-velocity is desired for the actuator. We validated this approach on a metal forming machine using simulation. Our results show that the proposed system can replace conventional single-pump drives in relevant applications because the overall system's behavior remains as expected, but the hydraulic pumps always rotate fast enough to avoid critical issues due to overheating, control instability, and low efficiency. The proposed drive is also torque-limiting, which means that downsizing of the electric motor is possible in favor of the system cost-effectiveness and compactness.