Session: Digital Hydraulic

Paper Number: 111865

111865 - A Digital Hydraulic Full-Bridge Oscillation Transformer 

As emission standards around the world grow more stringent, construction equipment manufacturers are looking towards electrification. A variety of electrified machines are being brought to market, dramatically reducing emissions of carbon dioxide, nitrogen oxide and acoustic noise. However, electrification comes with challenges as the machine’s ability to perform a full day’s work on a single charge is imperative. OEMs must balance battery cost with the power and range requirements of the machine without creating price-prohibitive products. Adding extra battery power to enable longer runtime adds expense, and therefore in the pursuit to balance extended runtime, without excessive battery costs, the inefficiency of hydraulics is the prime target.

In this paper we present a novel linear transformer based on the digital displacement technology. The transformer differ from other linear topologies in that the piston is free-floating and the chambers are operated similar to digital displacement unit chambers, where switching losses are minimized with timely operation of the low- and high-pressure manifold valves in relation to the compression and decompression of the displacement chamber. While exhibiting the disadvantage of a single piston machine in terms of vibrations, the mechanical construction of the transformer is simple compared to rotational piston-type displacement units, however the simplicity comes with the cost of difficulty in control. The research target is to develop a small, efficient, high-frequency transformer, which can be replace the inefficient control valves in common-pressure-rail systems.

A prototype designed for operation of the boom in an electrified wheel loader is presented. The prototype is implemented in this loader and the test results are presented. The performance is evaluated, and the efficiency is compared to the original wheel loader valve-cylinder boom drive.

Presenting Author: Per Johansen Aalborg University

Presenting Author Biography: Per Johansen received the B.Sc. and M.Sc. degrees in electromechanical systems engineering and the Ph.D. degree in mechanical engineering, for his studies in tribodynamic modeling, all from the Aalborg University, Aalborg,
Denmark in 2009, 2011, and 2014, respectively. Since 2014, he has been at the Department of Energy Technology, Aalborg University, where he now holds the position as Associate Professor. His main research interests include
Fluid power, Tribomechatronics and Sonomechatronics.