Analysis of electro-hydraulic lifting system's energy efficiency with direct electric drive pump control

Energy efficiency has become a major research issue in all fields of engineering. Opportunities of utilizing electric servo drives in the control of hydraulic lifting systems directly by an electric-servomotor-driven hydraulic machine and enabling energy recovery in them are studied. In this paper, the modelling and testing of an electro-hydraulic lifting and lowering system and a forklift with two lifting zones are carried out and analyzed. The efficiencies and energy-saving ratios of the experimental drive system are determined for the free lift and the second lift zones of a modified industrial forklift with different speeds and payloads. The maximum achieved energy-saving value in the Potential Energy Recovery System (PERS) was 50% for a maximum tested payload of 1000 kg and a maximum fork velocity of 0.5 m/s for the second lift zone. The efficiencies and energy consumptions of the experimental drive system and its components are determined. (C) 2012 Elsevier B.V. All rights reserved.