A Gasless Reservoir Solution for Electro-Hydraulic Compact Drives with Two Prime Movers

Søren Ketelsen, Damiano Padovani, Morten Kjeld Ebbesen, Torben Ole Andersen, Lasse Schmidt

Publikation: Bidrag til bog/antologi/rapport/konference proceedingKonferenceartikel i proceedingForskningpeer review

8 Citationer (Scopus)


Due to an increased focus on improving the energy efficiency and compactness of hydraulic linear actuators, the electro-hydraulic compact drive (ECD) has received increased attention lately. In this study the ECD consists of variable-speed electric motors and fixed-displacement pumps, which are directly connected to the cylinder, thus controlling the linear motion in a throttleless manner. Furthermore, ECDs are self-contained systems, i.e. based on a fully enclosed oil circuit, in order to avoid external contamination and air to enter the system and to increase system compactness. Conventionally a low-pressure gas-loaded accumulator is used as an oil reservoir to compensate for the flow imbalance occurring whenever utilizing single-rod cylinders in closed systems. The accumulator pressure is to be kept relatively low to stay within the required limits governed by the permitted pump housing’s pressure. Generally, this pressure is not allowed to exceed 1–3 bar. To avoid violating this limitation, the gas volume must be significantly larger than the actual oil volume, which needs to be stored in the accumulator. This requirement decreases the obtainable compactness of the ECD, especially for systems with a large cylinder stroke. Furthermore, the accumulator represents a potential of gas leakage, which ultimately could result in the ECD being non-functional. This paper presents a gasless reservoir solution, improving the system compactness and avoiding the risk of gas leakage. The proposed solution is based on a bootstrap reservoir which is charged by the lowest cylinder chamber pressure. This strategy is feasible for the class of ECDs that is capable of controlling the lowest cylinder chamber pressure alongside the cylinder motion. An ECD consisting of two electric prime movers is considered as a case study. It is shown how the gasless reservoir may be integrated into the system, and an analysis of how this affects the operating range and the dynamic couplings of the system is presented. This leads to the derivation of a control strategy for the Multi-Input-Multi-Output (MIMO) system based on state decoupling, by defining virtual inputs to control virtual outputs. A numerical study suggests that the reservoir volume may be reduced by approximately 50% for the given system dimensions. The proposed control strategy shows good position tracking performance while also being able to control the reservoir pressure within the pre-defined limits of 1 to 3 bar.

TitelProceedings of the 2020 ASME/BATH Symposium on Fluid Power and Motion Control
Antal sider13
ForlagAmerican Society of Mechanical Engineers
Publikationsdatookt. 2020
ISBN (Elektronisk)978-0-7918-8375-4
StatusUdgivet - okt. 2020
Begivenhed2020 Bath/ASME Symposium on Fluid Power and Motion Control - University of Bath, Bath, Storbritannien
Varighed: 9 sep. 202011 sep. 2020


Konference2020 Bath/ASME Symposium on Fluid Power and Motion Control
LokationUniversity of Bath


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