Abstract
Direct driven hydraulic drives (DDH) have the advantages of compact high power density in hydraulic systems and flexible control of electric motors. These advantages can benefit non-road mobile machinery (NRMM) applications. However, maintaining high efficiency while working in sub-zero conditions with NRMM is challenging. Therefore, this paper investigates the effect of hydraulic oil on the efficiency of a DDH in a cold environment for an NRMM application. In the DDH setup, the speed and position control of a double-acting cylinder was implemented directly with an electric motor drive in a closed-loop system without the conventional control valves. Efficiency measurements of the DDH setup with two oils (conventional multi-grade and high-performance) were conducted under different operating conditions (speed and payload) and environmental conditions (temperature in °C). The paper provides an evaluation of the electro-hydraulic system and a discussion on the usage of hydraulic oil by non-road mobile working machines in sub-zero conditions. An experimental investigation demonstrated an improvement in efficiency of 5%-unit at 22 °C, from 2%-unit to 5%-unit at 3 °C, and of almost a 10%-unit at temperatures below zero (−10 °C) by changing oil.
Highlights
Efficiency and operational costs are key factors driving the non-road mobile machine (NRMM)industry today
The paper provides an evaluation of the electro-hydraulic system and a discussion on the usage of hydraulic oil by non-road mobile working machines in sub-zero conditions
An experimental investigation demonstrated an improvement in efficiency of 5%-unit at 22 ◦ C, from 2%-unit to 5%-unit at 3 ◦ C, and of almost a 10%-unit at temperatures below zero (−10 ◦ C)
Summary
Efficiency and operational costs are key factors driving the non-road mobile machine (NRMM)industry today. Academic studies related to construction are concentrating on electrification and hybridization [3,4,5,6,7] In response to these demands, the NRMM market has created new products with fully and partially electrified machines [8,9,10,11]. Most of these market examples concentrate on meeting regulation demands while at the same time achieving attractive cost reductions, whereas academic studies mostly concentrate on efficiency. All of these mentioned methods require significant changes in NRMM and monitoring of expenses
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