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Mode Switching and Energy Recuperation in Open-Circuit Pump Control
Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology. (Fluid och mekanisk systemteknik)
Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
2007 (English)In: The 10th Scandinavian International Conference on Fluid Power, Tampere, Finland, Tampere, Finland: Tampere University of Technology , 2007, 197-209 p.Conference paper (Refereed)
Abstract [en]

Today´s mobile machines most often contain hydraulic valve controlled drives in an open loop circuit. For the purpose of saving energy, the constant pressure pumps have in the past frequently been replaced by load-sensing pumps and load-sensing valves. However, considering applications where the load is helped by the gravitational force, even these hydraulic systems often suffer from poor efficiency. In this article, a novel pump-controlled hydraulic system is studied where energy recuperation from lowering motions is posssible. The pumps are fully displaceable in both directions, working as motors when lowering loads. The amount of recuperated energy is highly dependent of the chosen control strategy, the hydromechanical properties as well as the target application. Furthermore, the article describes how valve design becomes an important feature in an attempt to reach high efficiency and machine operability.

Place, publisher, year, edition, pages
Tampere, Finland: Tampere University of Technology , 2007. 197-209 p.
Keyword [en]
Pump control open circuit energy efficiency energy recuperation
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:liu:diva-16075OAI: diva2:133010
Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2009-04-30Bibliographically approved
In thesis
1. Saving Energy in Construction Machinery using Displacement Control Hydraulics: Concept Realization and Validation
Open this publication in new window or tab >>Saving Energy in Construction Machinery using Displacement Control Hydraulics: Concept Realization and Validation
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the sector of mobile hydraulics, valve controlled systems are predominant. In these systems the load force and speed are adjusted by control valves. In machines where multiple drives are used in parallel at extremely varying loads the energy efficiency of such systems is often compromised over large working regions. Most valve controlled systems also lack the possibility to recuperate potential energy.

A different category of hydraulic systems, called displacement controlled hydraulics are based on the manipulation of the hydraulic flow using the relative displacement of the hydraulic machines as the final control element. This type of hydrostatic power transfer, yields a resistance free velocity control, ideally leading to lossless load actuation.

This thesis concerns the introduction of a new type of displacement controlled hydraulic system, adapted for construction machinery. The system decouples the hydraulic functions using one dedicated hydraulic machine for each drive. These machines are of open circuit type, capable of over center operation which enables energy recuperation. The system also comprises four separate valves that by means of switching allow the cylinder to be controlled over all four load quadrants. Depending on the selected valve hardware, the system may also include features available in a conventional valve controlled system, such as meter-out flow control. The system supports both symmetrical and asymmetrical cylinders. However, using the asymmetrical type the load may be controlled in two distinct states of operation. This yields an increased region of operation, which is otherwise generally stated as a drawback in displacement controlled systems. It also allows the selection between different control modes, where one of the modes is always more efficient than another.

In this research both theoretical studies and a practical implementation demonstrate the energy related benefits of the new concept. The target application of this study is a medium-size wheel loader. Measurement results using the wheel loader in a short truck loading cycle show a 10% percent reduction in fuel consumption. According to the theoretical investigation, this corresponds to a 20% reduction in energy consumption for the hydraulicsystem itself.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 117 p.
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1372
National Category
Fluid Mechanics and Acoustics
urn:nbn:se:liu:diva-15588 (URN)LIU-TEK-LIC-2008:30 (Local ID)978-91-7393-860-0 (ISBN)LIU-TEK-LIC-2008:30 (Archive number)LIU-TEK-LIC-2008:30 (OAI)
A35, A-huset, Campus Valla, Linköpings universitet, Linköping, Sweden (English)
Available from: 2009-01-07 Created: 2008-11-19 Last updated: 2009-04-30Bibliographically approved

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