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Evaluating a Pump Controlled Open Circuit Solution
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik.
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik.
2008 (Engelska)Ingår i: International Exposition for Power Transmission, Nevada, USA: Proceedings of the 51:st IFPE, Nevada, USA: Omnipress , 2008, s. 681-694Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
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 For the purpose of saving energy the constant pressure pumps have, in the past, often been replaced by load-sensing pumps and load-sensing valves. In mobile applications these load-sensing solutions have significantly reduced the energy consumption. However, in applications with unequal drive pressure levels the load sensing systems still result in energy losses, referred to as metering losses. Throttling losses associated to load lowering have also been paid more attention to in the energy debates. By instead adopting direct pump displacement control, with the capability of energy recuperation in lowering motions, many of these losses can be avoided. In this article the author has studied a hydraulic system configuration where each actuator/supply system comprises an electrically controlled variable displacement pump/motor working in an open-circuit together with four separate electrically controlled valves. The four valves render a solution versatile in control, as the cylinder chambers can be connected to pump and/or tank as well as be closed at any time. Depending on how the valves are controlled different modes of operation are achieved, which in turn yields different total energy efficiency depending on the present working point. In this study the performance, operability and energy consumption is evaluated in a wheel loader that is first looked upon with its original load sensing hydraulic system and then modified with a completely new pump controlled hydraulic system. Measurements published in this article demonstrate the advantages and drawbacks of pump control in an open circuit compared to a load sensing system. Performance is evaluated by looking at productivity, loading capacity and duty cycle time of a typical loading cycle. Operability is evaluated by looking at response times, load oscillations and driver comfort. Theoretical calculations of energy efficiency including metering and throttling losses over the valves as well as pump efficiency, line losses and losses in the recuperation phase are evaluated and validated. The fuel consumption of the pump-controlled wheel loader is measured and put side by side to measurements of the same machine equipped with a load-sensing hydraulic system.

Ort, förlag, år, upplaga, sidor
Nevada, USA: Omnipress , 2008. s. 681-694
Nyckelord [en]
Pump control, energy recuperation, mode switching
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
URN: urn:nbn:se:liu:diva-16074OAI: oai:DiVA.org:liu-16074DiVA, id: diva2:133008
Tillgänglig från: 2009-01-07 Skapad: 2009-01-07 Senast uppdaterad: 2009-04-30Bibliografiskt granskad
Ingår i avhandling
1. Saving Energy in Construction Machinery using Displacement Control Hydraulics: Concept Realization and Validation
Öppna denna publikation i ny flik eller fönster >>Saving Energy in Construction Machinery using Displacement Control Hydraulics: Concept Realization and Validation
2008 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2008. s. 117
Serie
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1372
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:liu:diva-15588 (URN)LIU-TEK-LIC-2008:30 (Lokalt ID)978-91-7393-860-0 (ISBN)LIU-TEK-LIC-2008:30 (Arkivnummer)LIU-TEK-LIC-2008:30 (OAI)
Presentation
A35, A-huset, Campus Valla, Linköpings universitet, Linköping, Sweden (Engelska)
Opponent
Handledare
Tillgänglig från: 2009-01-07 Skapad: 2008-11-19 Senast uppdaterad: 2020-03-29Bibliografiskt granskad

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