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  • 1.
    Achten, Peter A J
    et al.
    Innas BV, Breda, Netherlands.
    Vael, Georges E M
    Innas BV, Breda, Netherlands.
    Heybroek, Kim
    Volvo Construction Equipment, Eskilstuna, Sweden.
    Efficient hydraulic pumps, motors and transformers for hydraulic hybrid systems in mobile machinery2011In: VDI-Fachkonferenz Getriebe in Mobilen Arbeitsmaschinen, Düsseldorf: VDI-Wissensforum , 2011, p. 1-19Conference paper (Refereed)
    Abstract [en]

    A detailed simulation of a large 33 metric ton wheel loader, carrying out the short loading cycle, has been performed. Two systems have been compared and examined side by side:

    • The conventional system, having a mechanical transmission for driving the wheels and a conventional load sensing hydraulic circuit for the work and steering cylinders.
    • A new hydraulic hybrid system for the wheel drive and the implements, applying new and efficient hydrau- lic pumps and motors.The core of the new system is the hydraulic transformers which convert and control all the hydraulic power flows inside the loader.

    The new system results in a reduction of the fuel consumption of about 50% in the analyzed cycle. The new transmission and hydraulic system also results in a strong reduction of the cooler demands.

    Download full text (pdf)
    Efficient hydraulic pumps, motors and transformers for hydraulic hybrid systems in mobile machinery
  • 2. Order onlineBuy this publication >>
    Heybroek, Kim
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    On Energy Efficient Mobile Hydraulic Systems: with Focus on Linear Actuation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this dissertation, energy efficient hydraulic systems are studied. The research focuses on solutions for linear actuators in mobile applications, with emphasis on construction machines. Alongside the aspect of energy efficiency, the thesis deals with competing aspects in hydraulic system design found in the development of construction machines. Simulation models and controls for different concepts are developed, taking the whole machine into account. In line with this work, several proof of concept demonstrators are developed.

    First, pump controlled systems are studied and a novel concept based on an open-circuit pump configuration is conceived. Special consideration is paid to multi-mode capabilities that allow for a broadened operating range and potential downsizing of components. Simulation models and controls are developed and the system is experimentally validated in a wheel loader application.

    Second, the possibility for energy recuperation in valve controlled systems is investigated. In such solutions, a hydraulic motor, added to the meter-out port, is used for energy recovery during load lowering and in multi-function operation. Recuperated energy is either be used momentarily or is stored in a hydraulic accumulator. The proposed solution means an incremental improvement to conventional systems, which is sometimes attractive to machine manufacturers due to fewer uncertainties in reliability, safety and development cost. The energy recovery system is studied on a conceptual level where several alternative systems are proposed and a concept based on a two-machine hydraulic pressure transformer is selected for a deeper control study followed by experimental validation.

    Third, so-called `common pressure rail' systems are suggested. This technique is well established for rotary drives, at least for the industrial sector. However, in applying this technique to mobile hydraulics, feasible solutions for linear actuators are needed. In this dissertation, two approaches to this problem are presented. The first one is the hydraulic pressure transformer, studied in simulation as the key-component of a `series hybrid' topology for wheel loaders. In the second approach variable displacement linear actuators (VDLA) based on a 4-chamber cylinder and multi-mode control is applied. In a theoretical study a model predictive control approach is suggested and new insights to the trade-off between controllability and energy efficiency of a multi-chamber cylinder are presented. Finally, a fullscale hydraulic hybrid system based on secondary controlled hydraulic motors and VDLAs is designed and experimentally validated on a large excavator.

    List of papers
    1. Applied Control Strategies for a Pump Controlled Open Circuit Solution
    Open this publication in new window or tab >>Applied Control Strategies for a Pump Controlled Open Circuit Solution
    2008 (English)In: Proceedings of the 6:th IFK: International Fluid Power Conference, Dresden, Germany, Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V. , 2008, p. 39-52Conference paper, Published paper (Other academic)
    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 a 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. The pump is electrically controlled and is used either in pressure control mode or flow control mode depending on the state of operation. Along with the hardware described above, the open-circuit solution requires a number of electronic sensors as well as a microprocessor control system, hence the system is a mechatronic system. In contrast to a conventional hydraulic system the control objectives in this concept are not strictly defined by the hardware configuration, but instead many of its critical parameters can be adjusted in software, thus an increased flexibility in system design is obtained. Consequently, defining the desired system properties becomes even more important. Furthermore system robustness must be considered to a greater extent, due to the increased number of sensors and components. The main focus in this paper is to show how machine operability and performance depends on a set of chosen control strategies, what can be achieved as to energy efficiency and driver comfort and at what cost. Additionally the trade-off between energy efficiency and comfort is discussed. In previous work the author has investigated the influence on energy efficiency by lowering loads in different modes of operation, in respect to how the valves are controlled. In this article strategies to decide which mode of operation is the most energy efficient are considered, and how transitions between these modes can be handled by pressure matching prior to opening valves. As the open circuit solution does not support energy storage over time, methods to manage recuperated excess energy is investigated in order to prevent the primary mover from speeding up. The author will also discuss some application specific challenges where a wheel loader has been equipped with the open-circuit solution. For instance, how to handle interference between drives due to the mechanical coupling in the lifting framework and how to handle load actuation over gravity center.

    Place, publisher, year, edition, pages
    Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V., 2008
    Keywords
    Pump control, control strategies, energy recuperation, mode switching
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-16073 (URN)
    Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-10-26Bibliographically approved
    2. Modelling and Control of a Complementary Energy Recuperation System for Mobile Working Machines
    Open this publication in new window or tab >>Modelling and Control of a Complementary Energy Recuperation System for Mobile Working Machines
    2013 (English)In: / [ed] Petter Krus, Magnus Sethson, Liselott Ericson, Linköping: Linköping University Electronic Press, 2013, p. 21-30Conference paper, Published paper (Refereed)
    Abstract [en]

    The concept of hybrid technologies for mobile working machines has gained increased attention in recent years. This paper deals with a parallel hybrid system for energy recuperation based on a two-machine hydraulic transformer. The system can be connected hydraulically to an existing hydraulic circuit as a complementary add-on system. The linear analysis of the system visualises the control difficulties coming from a low inertia, slow control dynamics of the machines and the non-linear stick-slip friction during low speeds. A control strategy based on linear control methods is proposed and evaluated in a hardware test bench. It is shown that an acceptable performance can be achieved even with fairly simple models. Additionally, a start-up procedure is proposed to start the transformer from zero speed

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2013
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 092
    Keywords
    Parallel hybrid, Energy recuperation, Hydraulic transformer
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:liu:diva-100142 (URN)10.3384/ecp1392a3 (DOI)978-91-7519-572-8 (ISBN)
    Conference
    13th Scandinavian International Conference on Fluid Power, June 3-5, 2013, Linköping, Sweden
    Available from: 2013-10-29 Created: 2013-10-29 Last updated: 2018-02-02Bibliographically approved
    3. Towards Resistance-free Hydraulics in Construction Machinery
    Open this publication in new window or tab >>Towards Resistance-free Hydraulics in Construction Machinery
    2012 (English)In: 8th International Fluid Power Conference, Dresden: Dresdner Verein zur Förderung der Fluidtechnik , 2012, Vol. 2, p. 123-138Conference paper, Published paper (Refereed)
    Abstract [en]

    The topic of resistance-free motion control refers to solutions that minimize or completely eliminate the need for proportional valves, hence avoiding the throttling losses associated with metering. Previous research by the authors shows how a secondary control system could be used to improve energy efficiency in construction machines. The proposed solution uses hydraulic transformers, powered by a common pressure rail system driving both the linear work implements and the rotary drives of a propulsion system in a wheel loader. An emphasis in this paper is on the sizing aspects of transformer-based system design. The solution under special observation enables the use of smaller transformers utilizing the differential cylinder as a two-stage gearbox by means of “short-circuiting” its two cylinder chambers. The results and outlook from this study touch on how state-of-the-art secondary control systems could improve the energy efficiency of future construction machinery and suggest potential areas of improvement.

    Place, publisher, year, edition, pages
    Dresden: Dresdner Verein zur Förderung der Fluidtechnik, 2012
    National Category
    Other Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-132927 (URN)
    Conference
    8th International Fluid Power Conference, Dresden, March 26-28, 2012
    Funder
    Swedish Energy Agency, P32064-1
    Available from: 2016-12-01 Created: 2016-12-01 Last updated: 2017-10-26Bibliographically approved
    4. A novel hydromechanical hybrid motion system for construction machines
    Open this publication in new window or tab >>A novel hydromechanical hybrid motion system for construction machines
    2017 (English)In: International Journal of Fluid Power, ISSN 1439-9776, Vol. 18, no 1, p. 17-28Article in journal (Refereed) Published
    Abstract [en]

    This paper deals with a novel type of hybrid motion system for construction machines based on a common pressure rail shared between a hydromechanical power-split transmission and secondary controlled work hydraulics. A construction machine with driveline and work functions is a complex coupled motion system and the design of an effective hybrid system needs to take both subsystems into account. Studies on energy efficient hybrid systems for construction machines have hitherto principally focused on one subsystem at a time - work hydraulics or driveline. The paper demonstrates a use case with a specific transmission concept proposal for a medium-sized wheel loader. The system is modelled and simulated using an optimal energy management strategy based on dynamic programming. The results show the benefits of a throttle-free bidirectional link between the machine's subsystems and the energy storage, while taking advantage of the complex power flows of the power-split transmission.

    Place, publisher, year, edition, pages
    Abingdon, UK: Taylor & Francis, 2017
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-142329 (URN)10.1080/14399776.2016.1210423 (DOI)
    Available from: 2017-10-26 Created: 2017-10-26 Last updated: 2017-11-09Bibliographically approved
    Download full text (pdf)
    On Energy Efficient Mobile Hydraulic Systems: with Focus on Linear Actuation
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  • 3.
    Heybroek, Kim
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems.
    Pumpstyrd arbetshydraulik i hjullastare2007Conference paper (Other academic)
  • 4. Order onlineBuy this publication >>
    Heybroek, Kim
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems.
    Saving Energy in Construction Machinery using Displacement Control Hydraulics: Concept Realization and Validation2008Licentiate 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.

    List of papers
    1. Mode Switching and Energy Recuperation in Open-Circuit Pump Control
    Open this publication in new window or tab >>Mode Switching and Energy Recuperation in Open-Circuit Pump Control
    2007 (English)In: The 10th Scandinavian International Conference on Fluid Power, Tampere, Finland, Tampere, Finland: Tampere University of Technology , 2007, p. 197-209Conference paper, Published 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
    Keywords
    Pump control open circuit energy efficiency energy recuperation
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-16075 (URN)
    Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2009-04-30Bibliographically approved
    2. Applied Control Strategies for a Pump Controlled Open Circuit Solution
    Open this publication in new window or tab >>Applied Control Strategies for a Pump Controlled Open Circuit Solution
    2008 (English)In: Proceedings of the 6:th IFK: International Fluid Power Conference, Dresden, Germany, Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V. , 2008, p. 39-52Conference paper, Published paper (Other academic)
    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 a 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. The pump is electrically controlled and is used either in pressure control mode or flow control mode depending on the state of operation. Along with the hardware described above, the open-circuit solution requires a number of electronic sensors as well as a microprocessor control system, hence the system is a mechatronic system. In contrast to a conventional hydraulic system the control objectives in this concept are not strictly defined by the hardware configuration, but instead many of its critical parameters can be adjusted in software, thus an increased flexibility in system design is obtained. Consequently, defining the desired system properties becomes even more important. Furthermore system robustness must be considered to a greater extent, due to the increased number of sensors and components. The main focus in this paper is to show how machine operability and performance depends on a set of chosen control strategies, what can be achieved as to energy efficiency and driver comfort and at what cost. Additionally the trade-off between energy efficiency and comfort is discussed. In previous work the author has investigated the influence on energy efficiency by lowering loads in different modes of operation, in respect to how the valves are controlled. In this article strategies to decide which mode of operation is the most energy efficient are considered, and how transitions between these modes can be handled by pressure matching prior to opening valves. As the open circuit solution does not support energy storage over time, methods to manage recuperated excess energy is investigated in order to prevent the primary mover from speeding up. The author will also discuss some application specific challenges where a wheel loader has been equipped with the open-circuit solution. For instance, how to handle interference between drives due to the mechanical coupling in the lifting framework and how to handle load actuation over gravity center.

    Place, publisher, year, edition, pages
    Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V., 2008
    Keywords
    Pump control, control strategies, energy recuperation, mode switching
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-16073 (URN)
    Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-10-26Bibliographically approved
    3. Evaluating a Pump Controlled Open Circuit Solution
    Open this publication in new window or tab >>Evaluating a Pump Controlled Open Circuit Solution
    2008 (English)In: International Exposition for Power Transmission, Nevada, USA: Proceedings of the 51:st IFPE, Nevada, USA: Omnipress , 2008, p. 681-694Conference paper, Published paper (Other academic)
    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.

    Place, publisher, year, edition, pages
    Nevada, USA: Omnipress, 2008
    Keywords
    Pump control, energy recuperation, mode switching
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-16074 (URN)
    Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2009-04-30Bibliographically approved
    Download full text (pdf)
    FULLTEXT01
    Download (pdf)
    COVER01
  • 5.
    Heybroek, Kim
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Larsson, Jonas
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Palmberg, Jan-Ove
    Mode Switching and Energy Recuperation in Open-Circuit Pump Control2007In: The 10th Scandinavian International Conference on Fluid Power, Tampere, Finland, Tampere, Finland: Tampere University of Technology , 2007, p. 197-209Conference 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.

    Download full text (pdf)
    FULLTEXT01
  • 6.
    Heybroek, Kim
    et al.
    Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
    Larsson, Jonas
    Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
    Palmberg, Jan-Ove
    Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
    Open Circuit Solution for Pump Controlled Actuators2006In: Proceedings of the 4th FPNI-PhD Symposium, Sarasota 2006 : an initiative of Fluid Power Net International; Sarasota, Florida, USA, June 13 - 17, 2006 / [ed] Monika Ivantysynova, Sarasota: Coastal Printing , 2006, Vol. 1, p. 27-39Conference paper (Refereed)
    Abstract [en]

    Mobile machines of today often contain hydraulic valve controlled actuator loads 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 valves. In mobile applications, they have significantly reduced the energy consumption. Stricter environmental demands and rapidly increased fuel cost require an even lower consumption. By analyzing a typical working cycle of a construction machine, the possibility of energy recovery has been identified. The analyse confirms the importance of minimizing the metering losses. In a load-sensing valve solution these losses arise as a result of the unequal drive pressure levels. By adopting a displacement controlled regenerative solution, a significantly higher level of efficiancy can be obtained. 

    Download full text (pdf)
    Open Circuit Solution for Pump Controlled Actuators
  • 7.
    Heybroek, Kim
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology. Emerging Technologies, Volvo Construction Equipment, Eskilstuna, Sweden.
    Norlin, Erik
    Emerging Technologies, Volvo Construction Equipment, Eskilstuna, Sweden.
    Hydraulic Multi-Chamber Cylinders in Construction Machinery2015Conference paper (Other academic)
    Abstract [en]

    In mobile hydraulics double acting, two chamber, asymmetrical hydraulic cylinders are commonly used for linear motioncontrol. This paper shows how a cylinder instead using four chambers can improve fuel efficiency in construction machinery.In addition to this special multi-chamber cylinder the hydraulic systems presented in this study involves the use of discretelycontrolled on/off valves, hydraulic accumulators and secondary controlled hydraulic motors. The proposed system solutionsupports potential and kinetic energy recovery and storage using hydraulic accumulators. Through proper sizing of compon-ents and sophisticated control of simple on/off valves an energy efficient, flexible and robust system is achieved. This paperoutlines the basics behind this concept and provides some examples as to how the technology can be useful with an ambitionto reach new levels of energy efficiency in construction machines.

    Download full text (pdf)
    Hydraulic Multi-Chamber Cylinders in Construction Machinery
  • 8.
    Heybroek, Kim
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems .
    Palmberg, Jan-Ove
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems .
    Applied Control Strategies for a Pump Controlled Open Circuit Solution2008In: Proceedings of the 6:th IFK: International Fluid Power Conference, Dresden, Germany, Dresden: Dresdner Verein zur Förderung der Fluidtechnik e.V. , 2008, p. 39-52Conference paper (Other academic)
    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 a 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. The pump is electrically controlled and is used either in pressure control mode or flow control mode depending on the state of operation. Along with the hardware described above, the open-circuit solution requires a number of electronic sensors as well as a microprocessor control system, hence the system is a mechatronic system. In contrast to a conventional hydraulic system the control objectives in this concept are not strictly defined by the hardware configuration, but instead many of its critical parameters can be adjusted in software, thus an increased flexibility in system design is obtained. Consequently, defining the desired system properties becomes even more important. Furthermore system robustness must be considered to a greater extent, due to the increased number of sensors and components. The main focus in this paper is to show how machine operability and performance depends on a set of chosen control strategies, what can be achieved as to energy efficiency and driver comfort and at what cost. Additionally the trade-off between energy efficiency and comfort is discussed. In previous work the author has investigated the influence on energy efficiency by lowering loads in different modes of operation, in respect to how the valves are controlled. In this article strategies to decide which mode of operation is the most energy efficient are considered, and how transitions between these modes can be handled by pressure matching prior to opening valves. As the open circuit solution does not support energy storage over time, methods to manage recuperated excess energy is investigated in order to prevent the primary mover from speeding up. The author will also discuss some application specific challenges where a wheel loader has been equipped with the open-circuit solution. For instance, how to handle interference between drives due to the mechanical coupling in the lifting framework and how to handle load actuation over gravity center.

    Download full text (pdf)
    FULLTEXT01
  • 9.
    Heybroek, Kim
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems .
    Palmberg, Jan-Ove
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems .
    Evaluating a Pump Controlled Open Circuit Solution2008In: International Exposition for Power Transmission, Nevada, USA: Proceedings of the 51:st IFPE, Nevada, USA: Omnipress , 2008, p. 681-694Conference paper (Other academic)
    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.

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  • 10.
    Hugo, Anton
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Pettersson, Karl
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Heybroek, Kim
    Volvo Construction Equipment AB, Eskilstuna, Sweden.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Modelling and Control of a Complementary Energy Recuperation System for Mobile Working Machines2013In: / [ed] Petter Krus, Magnus Sethson, Liselott Ericson, Linköping: Linköping University Electronic Press, 2013, p. 21-30Conference paper (Refereed)
    Abstract [en]

    The concept of hybrid technologies for mobile working machines has gained increased attention in recent years. This paper deals with a parallel hybrid system for energy recuperation based on a two-machine hydraulic transformer. The system can be connected hydraulically to an existing hydraulic circuit as a complementary add-on system. The linear analysis of the system visualises the control difficulties coming from a low inertia, slow control dynamics of the machines and the non-linear stick-slip friction during low speeds. A control strategy based on linear control methods is proposed and evaluated in a hardware test bench. It is shown that an acceptable performance can be achieved even with fairly simple models. Additionally, a start-up procedure is proposed to start the transformer from zero speed

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  • 11.
    Pettersson, Karl
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology. Driveline Systems, Volvo Construction Equipment, Eskilstuna, Sverige.
    Heybroek, Kim
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology. Emerging Technologies, Volvo Construction Equipment, Eskilstuna, Sverige.
    Hydrauliskt hybridsystem för anläggningsmaskiner: Delat energilager är dubbelt energilager2015Conference paper (Other academic)
    Abstract [sv]

    Artikeln presenterar ett nytt innovativt hydrauliskt hybridkoncept med power-split transmission och delad hydraulisk krets med arbetsfunktionerna. Systemet är sekundärreglerat med direkt koppling till ett hydrauliskt energilager. Detta ger full frihet att överföra energi mellan drivlina, arbetsfunktioner och energilager i samtliga riktningar. En anläggningsmaskin medbåde framdrivning och arbetsfunktioner är ett komplext kopplat rörelsesystem och ett effektivt hybridkoncept måste därmed ta hänsyn till båda delsystemen. I sekundärreglerade system sker transformeringen av effekt i huvudsak vid lastsidan, detvill säga från hydraulisk effekt till mekanisk effekt. Sekundärreglering passar därför för hybridisering av maskiner med flera hydrauliska delsystem eftersom den hydrauliska kretsen kan användas gemensamt av systemen utan att använda strypventiler.Därmed blir även energilagret tillgängligt för delsystemen utan ytterligare effekttransformering.

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  • 12.
    Pettersson, Karl
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Heybroek, Kim
    Volvo Construction Equipment AB.
    Klintemyr, Andreas
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Analysis and control of a complementary energy recuperation system2012In: 8th International Fluid Power Conference Dresden: "Fluid Power Drives!", Dresden, 2012, p. 529-540Conference paper (Other academic)
    Abstract [en]

    In recent years, hybrid technologies have been in focus in both industry and academia.This paper deals with a hydraulically connected energy storage system based on a twomachinehydraulic transformer. Connecting the energy storage system hydraulically enableseasy disconnection and possibly fewer power domain transformations than with theconventional mechanically connected parallel hybrid structure. The control feasibility anddifferent control aspects are investigated and a control strategy is proposed. The controlstrategy is based on linear control techniques and it is shown that even with simple modelsof the system, sufficient control performance can be achieved.

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  • 13.
    Pettersson, Karl
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering. Driveline Systems, Volvo Construction Equipment, Eskilstuna, Sweden.
    Heybroek, Kim
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering. Emerging Technologies, Volvo Construction Equipment, Eskilstuna, Sweden.
    Mattsson, Per
    Driveline Systems, Volvo Construction Equipment, Eskilstuna, Sweden.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    A novel hydromechanical hybrid motion system for construction machines2017In: International Journal of Fluid Power, ISSN 1439-9776, Vol. 18, no 1, p. 17-28Article in journal (Refereed)
    Abstract [en]

    This paper deals with a novel type of hybrid motion system for construction machines based on a common pressure rail shared between a hydromechanical power-split transmission and secondary controlled work hydraulics. A construction machine with driveline and work functions is a complex coupled motion system and the design of an effective hybrid system needs to take both subsystems into account. Studies on energy efficient hybrid systems for construction machines have hitherto principally focused on one subsystem at a time - work hydraulics or driveline. The paper demonstrates a use case with a specific transmission concept proposal for a medium-sized wheel loader. The system is modelled and simulated using an optimal energy management strategy based on dynamic programming. The results show the benefits of a throttle-free bidirectional link between the machine's subsystems and the energy storage, while taking advantage of the complex power flows of the power-split transmission.

  • 14.
    Raduenz, Henrique
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Ericson, Liselott
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Heybroek, Kim
    Volvo Construction Equipment.
    De Negri, Victor J.
    Universidade Federal de Santa Catarina.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Improving the efficiency of valve-controlled systems by using multi-chamber actuators2021In: Proceedings of the 17:th Scandinavian International Conference on Fluid Power, SICFP’21, June 1-2, 2021, Linköping, Sweden, 2021, p. 224-236Conference paper (Refereed)
    Abstract [en]

    This paper outlines how multi-chamber actuatorscan improve the efficiency of valve-controlled systems.Resistive control is a major source of energy losses invalve-controlled systemsthat share the same pumpto drive multiple loads. In the proposed concept, by selectingdifferent chambers,the load on the multi-chamber actuator can be transformed into different pressure and flow rate levels, allowingthe adaptation of its load to the loads on otheractuators. Thiscan lead to a reduction of resistive control energy losses that occur between pump and actuatorswhen driven simultaneously.Suchsystemsareseen as an intermediate solution between resistive conventionalhydraulics and throttle-less digital hydraulics. As a casestudyto highlight the possible efficiency improvement, a concept of a load sensing system with a conventional and a multi-chamber actuatoris analysed. To determine itsefficiency,the equations that describe its static behaviour are presented. Evaluating them for a set ofload forces and speeds demonstrates how the load transformation occursand how it canimprove efficiency.

  • 15.
    Tozzi de Cantuaria Gama, Artur
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Heybroek, Kim
    Volvo CE.
    Ericson, Liselott
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    A Novel Multi-pump System for Hydraulic Actuation in Electric Mobile Machinery2022Conference paper (Refereed)
    Abstract [en]

    An observable trend nowadays is the change in the prime movers of mobile heavy machinery to electric alternatives to achieve more eco-friendly equipment. These solutions often require large and heavy batteries with limited capacity, making the research of more efficient components and the development of different system architectures an important topic of study. Hydraulic actuation is still a relevant application for these vehicles because of its reliability, controllability, and high power density. The electrification and digitalization of mobile machinery allow for innovative designs and control strategies to be implemented that take advantage of electro-hydraulic systems and their characteristics. Similar research has shown that a higher number of degrees of freedom allow for the system to operate with higher total efficiency. This paper introduces a novel actuation architecture that combines multiple fixed displacement hydraulic pumps and on/off directional valves to control the position and force of two hydraulic actuators for the working functions of a mobile machine. Each pump is powered by a variable speed electric drive so that each one can be operated independently, and together with the set of directional valves, allows the selection of different combinations of pumps and flow sharing between the actuators’ chambers to achieve the desired flow and pressure on each cylinder. The multi-pump system favours the use of smaller pumps, and the possibility of combining their flows reduces the need to operate the components at lower efficiency points such as partial displacement. At the same time, controlling the pumps’ flow through the variable-speed electric motors means that throttling valves are not needed. The development of this architecture will allow for its use in mathematical models to analyse its behaviour and efficiency and to obtain insights regarding points of improvement in the system architecture.

  • 16.
    Tozzi de Cantuaria Gama, Artur
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Heybroek, Kim
    Volvo Construction Equipment AB, Eskilstuna, Sweden.
    Ericson, Liselott
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    An Analysis of a Multi-Pump System for Actuator Operation in Electric Mobile Machinery2023In: ASME/BATH 2023 Symposium on Fluid Power and Motion Control - FPMC2023, The American Society of Mechanical Engineers , 2023Conference paper (Refereed)
    Abstract [en]

    This paper presents an analysis of a multi-pump solution for a hydraulic cylinder for application in mobile machinery with electric prime movers. The flexibility provided by using electric motors instead of an internal combustion engine allows for the design of alternative hydraulic architectures that remove the need for a centralized pumping system and support more direct control of individual components. This allows them to operate at a higher efficiency region to improve overall vehicle efficiency, leading to smaller batteries and shorter or less frequent recharge periods. To evaluate the capabilities of this proposal, this paper focuses on a backward calculation analysis of a single actuator operating with multiple pump/motors connected to each chamber. A series of hydraulic machines with fixed displacement and identical sizes are connected to the actuator chambers through on/off directional valves. The system controls the flow by using the required pumps and selecting their optimal speeds to minimize energy consumption or maximize energy recovery. The results show how the number of pumps affects the system’s performance and provide insights regarding the selection of operating machines according to the actuator speed and force.

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