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  • 1.
    Aevan, Nadjib Danial
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems.
    MDO Framework for Design of Human PoweredPropellers using Multi-Objective Genetic Algorithm2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis showcases the challenges, downsides and advantages to building a MultiDisciplinary Optimization (MDO) framework to automate the generation of an efficientpropeller design built for lightly loaded operation, more specifically for humanpowered aircrafts. Two years ago, a human powered aircraft project was initiatedat Linköping University. With the help of several courses, various students performedconceptional design, calculated and finally manufactured a propeller bymeans of various materials and manufacturing techniques. The performance ofthe current propeller is utilized for benchmarking and comparing results obtainedby the MDO process.The developed MDO framework is constructed as a modeFRONITER project wereseveral Computer Aided Engineering softwares (CAE) such as MATLAB, CATIAand XFOIL are connected to perform multiple consequent optimization subprocesses.The user is presented with several design constraints such as blade quantity,required input power, segment-wise airfoil thickness, desired lift coefficientetc. Also, 6 global search optimization algorithms are investigated to determinethe one which generate most efficient result according to several set standards.The optimization process is thereafter initialized by identifying the most efficientchord distribution with a help of an initial blade cross-section which has been previouslyused in other human powered propellers, the findings are thereafter usedto determine the flow conditions at different propeller stations. Two different aerodynamicoptimized shapes are generated with the help of consecutively performedsubprocesses. The optimized propeller requires 7.5 W less input power to generatenearly equivalent thrust as the original propeller with a total efficiency exceedingthe 90 % mark (90.25 %). Moreover, the MDO framework include an automationprocess to generate a CAD design of the optimized propeller. The generatedCAD file illustrates a individual surface blade decrease of 12.5 % compared tothe original design, the lightweight design and lower input power yield an overallpropulsion system which is less tedious to operate.

  • 2.
    Amadori, Kristian
    et al.
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Lundström, David
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Design Automation Framework for Micro Air Vehicles2009Conference paper (Other academic)
    Abstract [en]

    At Linköping University work has been done to automate the design process of Micro or Mini Air Vehicles. A design optimization framework that links together a CAD system for airframe design and panel code for aerodynamic design has been developed. This paper describes the experience made so far, and demonstrates a case study on fully automated design where a 3D printer is used for manufacturing.

  • 3.
    Amadori, Kristian
    et al.
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Lundström, David
    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.
    Automated Design and Fabrication of Micro Air Vehicles2011In: Journal of Aerospace Engineering, ISSN 0893-1321, E-ISSN 1943-5525, Vol. 226, no 10, p. 1271-1282Article in journal (Refereed)
    Abstract [en]

    A methodology for an automated design and fabrication of micro-air vehicles (MAVs) is presented. A design optimization framework has been developed that interfaces several software systems to generate MAVs to optimally fulfil specific mission requirements. By means of amulti-objective genetic algorithm, families of MAVs are tailored with respect to objectives such as weight and endurance. The framework takes into consideration the airframe and aerodynamic design as well as the selection and positioning of internal components. The selection of propulsion system components is made from a database of off-the-shelf components. In combination with a three-dimensional printer, physical prototypes can be quickly manufactured. A validation of the framework results from flight tests of a real MAV is also presented.

  • 4.
    Amadori, Kristian
    et al.
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Melin, Tomas
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Staack, Ingo
    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.
    Multidisciplinary Optimization of Wing Structure Using Parametric Models2013Conference paper (Other academic)
    Abstract [en]

    Aircraft design is an inherently multidisciplinary activity that requires integrating different models and tools to reach a well-balanced and optimized product. At Linköping University a design framework is being developed to support the initial design space exploration and the conceptual design phase. Main characteristics of the framework are its flexible database in XML format, together with close integration of automated CAD and other tools, which allows the developed geometry to be directly used in the subsequent preliminary design phase. In particular, the aim of the proposed work is to test the framework by designing, optimizing and studying a transport aircraft wing with respect to aerodynamic, geometry, structural and accessability constraints. The project will provide an initial assessment of the capability of the framework, both in terms of processing speed and accuracy of the results.

  • 5.
    Amadori, Kristian
    et al.
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Tarkian, Mehdi
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Ölvander, Johan
    Linköping University, Department of Management and Engineering, Machine Design. 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.
    Flexible and Robust CAD Models for Design Automation2012In: Advanced Engineering Informatics, ISSN 1474-0346, E-ISSN 1873-5320, Vol. 26, no 2, p. 180-195Article in journal (Refereed)
    Abstract [en]

    This paper explores novel methodologies for enabling Multidisciplinary Design Optimization (MDO) of complex engineering products. To realize MDO, Knowledge Based Engineering (KBE) is adopted with the aim of achieving design reuse and automation. The aim of the on-going research at Linköping University is to shift from manual modelling of disposable geometries to Computer Aided Design (CAD) automation by introducing generic high-level geometry templates. Instead of repeatedly modelling similar instances of objects, engineers should be able to create more general models that can represent entire classes of objects. The proposed methodology enables utilization of commercial design tools, hence taking industrial feasibility into consideration. High Level CAD templates (HLCt) will be proposed and discussed as the building blocks of flexible and robust CAD models, which in turn enables high-fidelity geometry in the MDO loop. Quantification of the terms flexibility and robustness is also presented, providing a means to measure the quality of the geometry models. Finally, application examples are presented in which the outlined framework is evaluated. The applications have been chosen from three ongoing research projects aimed at automating the design of transport aircraft, industrial robots, and micro air vehicles.

  • 6.
    Andersson, Håkan
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering. Construct Tools PC AB, Sweden.
    Nordin, Peter
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Borrvall, Thomas
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Leidermark, Daniel
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units2017In: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, no 2, p. 317-333Article in journal (Refereed)
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

  • 7.
    André, Samuel
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Optimization of Valve Damping2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Öhlins CES Technologies in Jönköping have in the last 30 years been developing control valves for semi active suspension systems used in the car industry. The system, marketed by Öhlins under the brand name CES (Continuously controlled Electronic Suspension), enables a wide working range and ability to adapt to the current road conditions. By controlling  the valve in different ways there are also possibilities to decide on a specfic damper characteristic such as sport or comfort.

    The CES valve is working as a pilot controlled pressure regulator and is continuously controlled with help of an electro magnet. The CES valve is mounted in a uniflow damper which in turn guarantees the flow through the valve to go in only one direction independently ofdamper stroke direction.

    The rst part of the thesis investigates the damping characteristics in the latest model of the CES valve (i.e the CES8700). A simulation model is made to approximate the damping in the solenoid plunger. Questions that are answered are: How is damping dened, what creates damping in the valve, how large is the damping, what parameters aect the damping. The second part of the thesis investigates new and already prototyped damping concepts with help of simulation. This has been done in order to optimize the valve damping and in turn the damper performance. The simulation results show that the valve dynamics can be improved but often at the expense of a slower valve.

  • 8.
    Arana Escobedo, André
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Gunnarsson, Oskar
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Hydraulic Energy Efficiency of Concepts on an Articulated Hauler: Design and evaluation of different hydraulic concepts with focus on energy efficiency2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master's thesis has evaluated dierent system designs for the hydraulic system on an articulated hauler at Volvo Construction Equipment (CE). The current system suers from great losses when running on low pump displacement settings. This is due to large installed displacements as a result of regulations and market demands. New system concepts have been generated and simulations in Matlab and Amesim show that some of the concepts can be implemented in order to increase energy eciency up to 65%. However, increasing eciency does in most cases also increase cost, making some of the concepts unrealistic to implement. The suggested solution for Volvo CE is to remove one pump and allow for the fan pumps to supply oil to the steering and dumping, as described in the Displacement reduction concept. They should also examine the possibility to implement clutches further.

  • 9.
    Axin, Mikael
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Arbetshydraulik i mobila maskiner2015Conference paper (Refereed)
    Abstract [sv]

    I mobila maskiner finns en mängd olika systemtyper för arbetshydrauliken. Det vanligaste är fortfarande det kostnadseffektivaoch robusta öppet-centrum systemet med fast pump. Det ger operatören en mjuk styrning med hög dämpning. Ennackdel är dock den låga energieffektiviteten. Under de senaste decennierna har det lastkännande systemet blivit mer ochmer populärt. Energieffektiviteten i detta system är högre även om tryck och flöde varierar stort över tid och mellan olikafunktioner. En nackdel är dock att systemets dämpning är låg. Det finns ett antal olika systemtyper som kombinerar en mjukstyrning med relativt hög energieffektivitet. Nyckeln är att begränsa flödet genom det öppna centrumet i riktningsventilen.Detta kan göras med en variabel tryckstyrd pump som regleras så att öppet-centrum flödet hålls på en konstant nivå. Alternativetär en flödesstyrd pump som styrs direkt från operatörens joystickkommandon eller via flödet i det öppna centrumet. Iden här artikeln görs en jämförande analys av olika systemtyper för arbetshydrauliken i mobila maskiner. Fokus ligger påenergieffektivitet, dynamiska egenskaper och pumpreglering. En genomgång av mer avancerade systemtyper såsom individuellastrypställen och pumpstyrda aktuatorer har också gjorts.

  • 10.
    Axin, Mikael
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Fluid Power Systems for Mobile Applications: with a Focus on Energy Efficiency and Dynamic Characteristics2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis studies an innovative working hydraulic system design for mobile applications. The purpose is to improve the energy efficiency and the dynamic characteristics compared to load sensing systems without increasing the complexity or adding additional components.

    The system analysed in this thesis is referred to as flow control. The fundamental difference compared to load sensing systems is that the pump is controlled based on the operator’s command signals rather than feedback signals from the loads. This control approach enables higher energy efficiency since the pressure difference between pump and load is given by the system resistance rather than a prescribed pump pressure margin. High power savings are possible especially at medium flow rates.

    Furthermore, load sensing systems suffer from poor dynamic characteristics since the pump is operated in a closed loop control mode. This might result in an oscillatory behaviour. Flow control systems have no stability issues attached to the load pressure feedback since there is none.

    Pressure compensators are key components in flow control systems. This thesis addresses the flow matching problem which occurs when using conventional compensators in combination with a flow controlled pump. Flow sharing pressure compensators solve this problem since the pump flow will be distributed between all active functions. A novel control approach where the directional valve is controlled without affecting the cylinder velocity with the objective of optimizing the damping is proposed.

    In this research, both theoretical studies and practical implementations demonstrate the capability of flow control systems. Experiments show a reduced pump pressure margin and energy saving possibilities in a short loading cycle for a wheel loader application.

    List of papers
    1. Energy Efficient Load Adapting System Without Load Sensing: Design and Evaluation
    Open this publication in new window or tab >>Energy Efficient Load Adapting System Without Load Sensing: Design and Evaluation
    2009 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    In load sensing systems, the pump pressure is controlled in a closed loop control mode. In this paper, a system solution where the displacement of the pump is controlled directly from the operator's demand is studied. Both the stability and the response is thereby improved. It also implies a better energy efficiency since the pump pressure will be adapted according to the point of operation with no additional pressure margin needed. In some mobile applications, pressure compensation is required to avoid load interference. When using common pre compensators in a displacement controlled system, the pump and the valve will both control the flow. A better solution would be to control the flow by the pump and utilize the valve as a flow divider. This can be achieved by using flow sharing compensators. It also allows further energy savings since the maximum restriction area of the main spool at one of the loads can be utilized independent of the flow delivered by the pump. This paper addresses the problem with using common pre compensators in displacement controlled systems and analyses and compares both a traditional load sensing system and an open controlled pump solution with flow sharing compensators. Measurements on a wheel loader application equipped with the system presented in this paper shows a decreased energy consumption of 14 % for the working hydraulics compared to a load sensing system during a short loading cycle, provided that the pump is not saturated.

    Place, publisher, year, edition, pages
    Linköping: , 2009
    Keywords
    fluid power, mobile systems, LS systems, pre compensation, energy efficiency, flow sharing
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-52691 (URN)
    Conference
    11th Scandinavian International Conference on Fluid Power, SICFP'09, June 2-4, Linköping, Sweden
    Available from: 2010-01-08 Created: 2010-01-08 Last updated: 2015-08-31Bibliographically approved
    2. Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
    Open this publication in new window or tab >>Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
    2011 (English)In: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11: Volume 2 / [ed] Harri Sairiala & Kari T. Koskinen, 2011, p. 223-238Conference paper, Published paper (Refereed)
    Abstract [en]

    Interest has increased in flow controlled systems in the field of mobile fluid power. The capital distinction between traditional load-sensing (LS) systems and flow controlled systems is that the pump is controlled based on the operator’s total flow demand rather than maintaining a certain pressure margin over the maximum load pressure. One of the main advantages of flow controlled systems is the absence of the feedback of the highest load pressure to the pump controller. In this paper, a dynamic analysis is performed where flow controlled and LS systems are compared. It is shown how instability can occur in LS systems due to the pump controller and proven that no such instability properties are present in flow controlled systems. A drawback with one type of flow controlled system is that the highest load dynamically will disturb the lighter loads. This paper shows a novel way to optimize the damping in such systems by controlling the opening position of the directional valve independently of the flow. The mentioned disturbance between the highest load to the others can thereby be reduced.

    Keywords
    Flow control, load sensing, dynamic analysis, stability, damping
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-68636 (URN)978-952-15-2519-3 (ISBN)
    Conference
    The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11, May 18-20, 2011 Tampere, Finland
    Available from: 2011-05-25 Created: 2011-05-25 Last updated: 2015-09-07
    3. Optimized Damping in Cylinder Drives Using the Meter-out Orifice: Design and Experimental Verification
    Open this publication in new window or tab >>Optimized Damping in Cylinder Drives Using the Meter-out Orifice: Design and Experimental Verification
    2012 (English)In: 8th International Fluid Power Conference Dresden: "Fluid Power Drives!", 2012, Vol. 1, p. 579-591Conference paper, Oral presentation only (Other academic)
    Abstract [en]

    This paper analyses the damping of a flow controlled cylinder with a mass load and an outlet orifice. By using linear models, a mathematical expression for the damping is derived. It is shown that the volumes on each side of the piston have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension; both smaller and larger orifice areas give low damping independently of the size of the volumes. In this paper a design is proposed of the outlet orifice area that optimizes the damping of the system. Experimental results which confirm the theoretical expectations are also presented. The conclusions are that without an outlet orifice, the hydraulic system will not contribute with any damping at all. Furthermore, large dead volumes in the cylinder will increase the damping, but at the expense of the system’s efficiency.

    Keywords
    Damping, compensator, outlet orifice, efficiency
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-76878 (URN)
    Conference
    8th International Fluid Power Conference, March 26 - 28, 2012, Dresden
    Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2015-09-07
  • 11.
    Axin, Mikael
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Mobile Working Hydraulic System Dynamics2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with innovative working hydraulic systems for mobile machines. Flow control systems are studied as an alternative to load sensing. The fundamental difference is that the pump is controlled based on the operator’s command signals rather than feedback signals from the loads. This control approach enables higher energy efficiency and there is no load pressure feedback causing stability issues. Experimental results show a reduced pump pressure margin and energy saving potential for a wheel loader application.

    The damping contribution from the inlet and outlet orifice in directional valves is studied. Design rules are developed and verified by experiments.

    A novel system architecture is proposed where flow control, load sensing and open-centre are merged into a generalized system description. The proposed system is configurable and the operator can realize the characteristics of any of the standard systems without compromising energy efficiency. This can be done non-discretely on-the-fly. Experiments show that it is possible to avoid unnecessary energy losses while improving system response and increasing stability margins compared to load sensing. Static and dynamic differences between different control modes are also demonstrated experimentally.

    List of papers
    1. Flow versus pressure control of pumps in mobile hydraulic systems
    Open this publication in new window or tab >>Flow versus pressure control of pumps in mobile hydraulic systems
    2014 (English)In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 228, no 4, p. 245-256Article in journal (Refereed) Published
    Abstract [en]

    This work studies an innovative working hydraulic system design for mobile applications, referred to as flow control. The fundamental difference compared to load-sensing systems is that the pump is controlled based on the operator’s command signals rather than feedback signals from the loads. This control approach enables higher energy efficiency since the pressure difference between pump and load is given by the system resistance rather than a prescribed pump pressure margin. Furthermore, load-sensing systems suffer from poor dynamic characteristics since the pump is operated in a closed-loop control mode. This might result in an oscillatory behaviour. Flow control systems have no stability issues attached to the load pressure feedback since there is none. This allows the pump to be designed to meet the response requirements without considering system stability. Pressure compensators are key components in flow control systems. This study addresses the flow matching problem which occurs when using traditional compensators in combination with a flow-controlled pump. Flow sharing pressure compensators solve this problem since the pump flow will be distributed between all active functions. Simulation results and measurements on a wheel loader application demonstrate the energy-saving potentials and the dynamic improvements for the flow control system.

    Place, publisher, year, edition, pages
    Sage Publications, 2014
    Keywords
    Hydraulics, flow control, load-sensing, mobile systems, energy efficiency, dynamic characteristics, compensators
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-105796 (URN)10.1177/0959651813512820 (DOI)000333799100005 ()
    Available from: 2014-04-07 Created: 2014-04-07 Last updated: 2017-12-05Bibliographically approved
    2. Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
    Open this publication in new window or tab >>Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
    2011 (English)In: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11: Volume 2 / [ed] Harri Sairiala & Kari T. Koskinen, 2011, p. 223-238Conference paper, Published paper (Refereed)
    Abstract [en]

    Interest has increased in flow controlled systems in the field of mobile fluid power. The capital distinction between traditional load-sensing (LS) systems and flow controlled systems is that the pump is controlled based on the operator’s total flow demand rather than maintaining a certain pressure margin over the maximum load pressure. One of the main advantages of flow controlled systems is the absence of the feedback of the highest load pressure to the pump controller. In this paper, a dynamic analysis is performed where flow controlled and LS systems are compared. It is shown how instability can occur in LS systems due to the pump controller and proven that no such instability properties are present in flow controlled systems. A drawback with one type of flow controlled system is that the highest load dynamically will disturb the lighter loads. This paper shows a novel way to optimize the damping in such systems by controlling the opening position of the directional valve independently of the flow. The mentioned disturbance between the highest load to the others can thereby be reduced.

    Keywords
    Flow control, load sensing, dynamic analysis, stability, damping
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-68636 (URN)978-952-15-2519-3 (ISBN)
    Conference
    The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11, May 18-20, 2011 Tampere, Finland
    Available from: 2011-05-25 Created: 2011-05-25 Last updated: 2015-09-07
    3. Optimized Damping in Cylinder Drives Using the Meter-out Orifice: Design and Experimental Verification
    Open this publication in new window or tab >>Optimized Damping in Cylinder Drives Using the Meter-out Orifice: Design and Experimental Verification
    2012 (English)In: 8th International Fluid Power Conference Dresden: "Fluid Power Drives!", 2012, Vol. 1, p. 579-591Conference paper, Oral presentation only (Other academic)
    Abstract [en]

    This paper analyses the damping of a flow controlled cylinder with a mass load and an outlet orifice. By using linear models, a mathematical expression for the damping is derived. It is shown that the volumes on each side of the piston have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension; both smaller and larger orifice areas give low damping independently of the size of the volumes. In this paper a design is proposed of the outlet orifice area that optimizes the damping of the system. Experimental results which confirm the theoretical expectations are also presented. The conclusions are that without an outlet orifice, the hydraulic system will not contribute with any damping at all. Furthermore, large dead volumes in the cylinder will increase the damping, but at the expense of the system’s efficiency.

    Keywords
    Damping, compensator, outlet orifice, efficiency
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-76878 (URN)
    Conference
    8th International Fluid Power Conference, March 26 - 28, 2012, Dresden
    Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2015-09-07
    4. A Hybrid of Pressure and Flow Control in Mobile Hydraulic Systems
    Open this publication in new window or tab >>A Hybrid of Pressure and Flow Control in Mobile Hydraulic Systems
    2014 (English)In: 9th InternationalFluid Power Conference (IFK). Vol. 1. Aachen, Germany, 24-26 March 2014 / [ed] Hubertus Murrenhoff, 2014, p. 190-201Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents a hybrid pump controller approach for mobile hydraulic systems, influenced by both pressure and flow. The controller is tuneable to be able to set the order of importance of the pressure and flow controller, respectively. It is thus possible to realize a load sensing system, a flow control system or a mix of the two. Using a low load pressure feedback gain and a high flow control gain, a system emerges with high energy efficiency, fast system response, high stability margins and no flow matching issues. In this paper, both theoretical studies and practical implementations demonstrate the capability of a hybrid pump control approach.

    Keywords
    Mobile hydraulics, pressure control, flow control, energy efficiency, dynamics
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-105794 (URN)978-3-9816480-0-3 (ISBN)
    Conference
    9th International Fluid Power Conference (IFK), 24-26 March 2014, Aachen, Germany
    Available from: 2014-04-07 Created: 2014-04-07 Last updated: 2015-09-07Bibliographically approved
    5. Energy Efficient Fluid Power System for Mobile Machines with Open-centre Characteristics
    Open this publication in new window or tab >>Energy Efficient Fluid Power System for Mobile Machines with Open-centre Characteristics
    2014 (English)In: 9th JFPS International Symposium on Fluid Power. Matsue, Japan, 28-31 October 2014, The Japan Fluid Power System Society , 2014, p. 452-459Conference paper, Published paper (Other academic)
    Abstract [en]

    This paper presents a flexible and energy efficient system solution which mimics the behaviour of an open-centre system. An electro-hydraulic variable displacement pump and closed-centre valves are used. Instead of having a flow in the open-centre gallery, that flow is calculated using a pressure sensor and a valve model. The variable pump is then controlled in order to only deliver the flow that would go to the actual loads. It is also possible for the operator to decide how much load dependency there should be. The extreme case is not having any load dependency at all, resulting in a system where the pump displacement setting is controlled according to the sum of all requested load flows. It is thus possible to realize a system design with open-centre characteristics, a flow control system or something in between. Each operator can thereby get their optimal control characteristic while having high energy efficiency.

    Place, publisher, year, edition, pages
    The Japan Fluid Power System Society, 2014
    Keywords
    Mobile hydraulics, energy efficiency, dynamics, damping
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-111819 (URN)4-931070-10-8 (ISBN)
    Conference
    9th JFPS International Symposium on Fluid Power, Shimane, Japan, 28-31 October 2014
    Available from: 2014-11-04 Created: 2014-11-04 Last updated: 2016-05-17Bibliographically approved
    6. A Flexible Working Hydraulic System for Mobile Machines
    Open this publication in new window or tab >>A Flexible Working Hydraulic System for Mobile Machines
    2016 (English)In: International Journal of Fluid Power, ISSN 1439-9776, Vol. 17, no 2, p. 79-89Article in journal (Other academic) Published
    Abstract [en]

    This paper proposes a novel working hydraulic system architecture for mobile machines. Load sensing, flow control and open-centre are merged into a generalized system description. The proposed system is configurable and the operator can realize the characteristics of any of the standard systems without compromising energy efficiency. This can be done non-discretely on-the-fly. One electrically controlled variable displacement pump supplies the system and conventional closed-centre spool valves are used. The pump control strategies are explained in detail. Experimental results demonstrate one solution to the flow matching problem and the static and dynamic differences between different control modes.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2016
    Keywords
    Mobile hydraulics, dynamics, energy efficiency, pump controller
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-121068 (URN)10.1080/14399776.2016.1141635 (DOI)
    Available from: 2015-09-04 Created: 2015-09-04 Last updated: 2017-12-04Bibliographically approved
  • 12.
    Axin, Mikael
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ökad dämpning genom rätt design av utloppsstrypningen2012In: Hydraulikdagarna 2012, Linköping, 2012Conference paper (Refereed)
    Abstract [sv]

    Svängningar är ett vanligt förekommande problem i hydrauliska system. Den här artikeln analyserar dämpningen i ett system bestående av en tryckkompenserad ventil, en cylinder samt en last. Genom att designa utloppsstrypningen i ventilen på ett bra sätt kan en hög dämpning erhållas. Resultaten som presenteras i den här artikeln kan ligga till grund vid systemdimensionering för att erhålla önskad dämpning i tryckkompenserade hydraulsystem. Volymerna på respektive sida av cylinderkolven har stor inverkan på dämpningen. Om inloppsvolymen är liten blir dämpningen låg. Det absolut viktigaste är dock att designa utloppsstrypningen på ett bra sätt. En optimal öppningsarea existerar; både mindre och större area ger lägre dämpning. I den här artikeln föreslås en design av utloppsstrypningen som optimerar dämpningen i det mest ogynnsamma fallet samtidigt som förlusterna över strypningen hålls relativt små. Experimentella resultat som bekräftar de teoretiska förväntningarna presenteras också.

  • 13.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    Parker Hannifin, Borås, Sweden.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    A Flexible Working Hydraulic System for Mobile Machines2016In: International Journal of Fluid Power, ISSN 1439-9776, Vol. 17, no 2, p. 79-89Article in journal (Other academic)
    Abstract [en]

    This paper proposes a novel working hydraulic system architecture for mobile machines. Load sensing, flow control and open-centre are merged into a generalized system description. The proposed system is configurable and the operator can realize the characteristics of any of the standard systems without compromising energy efficiency. This can be done non-discretely on-the-fly. One electrically controlled variable displacement pump supplies the system and conventional closed-centre spool valves are used. The pump control strategies are explained in detail. Experimental results demonstrate one solution to the flow matching problem and the static and dynamic differences between different control modes.

  • 14.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    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.
    A Hybrid of Pressure and Flow Control in Mobile Hydraulic Systems2014In: 9th InternationalFluid Power Conference (IFK). Vol. 1. Aachen, Germany, 24-26 March 2014 / [ed] Hubertus Murrenhoff, 2014, p. 190-201Conference paper (Refereed)
    Abstract [en]

    This paper presents a hybrid pump controller approach for mobile hydraulic systems, influenced by both pressure and flow. The controller is tuneable to be able to set the order of importance of the pressure and flow controller, respectively. It is thus possible to realize a load sensing system, a flow control system or a mix of the two. Using a low load pressure feedback gain and a high flow control gain, a system emerges with high energy efficiency, fast system response, high stability margins and no flow matching issues. In this paper, both theoretical studies and practical implementations demonstrate the capability of a hybrid pump control approach.

  • 15.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    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.
    Energy Efficient Fluid Power System for Mobile Machines with Open-centre Characteristics2014In: 9th JFPS International Symposium on Fluid Power. Matsue, Japan, 28-31 October 2014, The Japan Fluid Power System Society , 2014, p. 452-459Conference paper (Other academic)
    Abstract [en]

    This paper presents a flexible and energy efficient system solution which mimics the behaviour of an open-centre system. An electro-hydraulic variable displacement pump and closed-centre valves are used. Instead of having a flow in the open-centre gallery, that flow is calculated using a pressure sensor and a valve model. The variable pump is then controlled in order to only deliver the flow that would go to the actual loads. It is also possible for the operator to decide how much load dependency there should be. The extreme case is not having any load dependency at all, resulting in a system where the pump displacement setting is controlled according to the sum of all requested load flows. It is thus possible to realize a system design with open-centre characteristics, a flow control system or something in between. Each operator can thereby get their optimal control characteristic while having high energy efficiency.

  • 16.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    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.
    Flow versus pressure control of pumps in mobile hydraulic systems2014In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 228, no 4, p. 245-256Article in journal (Refereed)
    Abstract [en]

    This work studies an innovative working hydraulic system design for mobile applications, referred to as flow control. The fundamental difference compared to load-sensing systems is that the pump is controlled based on the operator’s command signals rather than feedback signals from the loads. This control approach enables higher energy efficiency since the pressure difference between pump and load is given by the system resistance rather than a prescribed pump pressure margin. Furthermore, load-sensing systems suffer from poor dynamic characteristics since the pump is operated in a closed-loop control mode. This might result in an oscillatory behaviour. Flow control systems have no stability issues attached to the load pressure feedback since there is none. This allows the pump to be designed to meet the response requirements without considering system stability. Pressure compensators are key components in flow control systems. This study addresses the flow matching problem which occurs when using traditional compensators in combination with a flow-controlled pump. Flow sharing pressure compensators solve this problem since the pump flow will be distributed between all active functions. Simulation results and measurements on a wheel loader application demonstrate the energy-saving potentials and the dynamic improvements for the flow control system.

  • 17.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Palmberg, Jan-Ove
    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.
    Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems2011In: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11: Volume 2 / [ed] Harri Sairiala & Kari T. Koskinen, 2011, p. 223-238Conference paper (Refereed)
    Abstract [en]

    Interest has increased in flow controlled systems in the field of mobile fluid power. The capital distinction between traditional load-sensing (LS) systems and flow controlled systems is that the pump is controlled based on the operator’s total flow demand rather than maintaining a certain pressure margin over the maximum load pressure. One of the main advantages of flow controlled systems is the absence of the feedback of the highest load pressure to the pump controller. In this paper, a dynamic analysis is performed where flow controlled and LS systems are compared. It is shown how instability can occur in LS systems due to the pump controller and proven that no such instability properties are present in flow controlled systems. A drawback with one type of flow controlled system is that the highest load dynamically will disturb the lighter loads. This paper shows a novel way to optimize the damping in such systems by controlling the opening position of the directional valve independently of the flow. The mentioned disturbance between the highest load to the others can thereby be reduced.

  • 18.
    Axin, Mikael
    et al.
    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.
    Design Rules for High Damping in Mobile Hydraulic Systems2013In: 13th Scandinavian International Conference on Fluid Power, Linköping University Electronic Press, 2013, p. 13-20Conference paper (Refereed)
    Abstract [en]

    This paper analyses the damping in pressure compensated closed centre mobile working hydraulic systems. Both rotational and linear loads are covered and the analysis applies to any type of pump controller. Only the outlet orifice in the directional valve will provide damping to a pressure compensated system. Design rules are proposed for how the system should be dimensioned in order to obtain a high damping. The volumes on each side of the load have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension for maximized damping; both smaller and larger orifice areas give lower damping independently of the volumes. This paper presents a method to dimension the outlet orifice area and the load volumes in order to obtain a desired system damping. Experimental results, which confirm the theoretical expectations, are also presented. The conclusions are that it is possible to obtain a high damping contribution from the outlet orifice if the system is dimensioned correctly. However, the energy efficiency needs to be considered while improving the damping

  • 19.
    Axin, Mikael
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Palmberg, Jan-Ove
    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.
    Optimized Damping in Cylinder Drives Using the Meter-out Orifice: Design and Experimental Verification2012In: 8th International Fluid Power Conference Dresden: "Fluid Power Drives!", 2012, Vol. 1, p. 579-591Conference paper (Other academic)
    Abstract [en]

    This paper analyses the damping of a flow controlled cylinder with a mass load and an outlet orifice. By using linear models, a mathematical expression for the damping is derived. It is shown that the volumes on each side of the piston have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension; both smaller and larger orifice areas give low damping independently of the size of the volumes. In this paper a design is proposed of the outlet orifice area that optimizes the damping of the system. Experimental results which confirm the theoretical expectations are also presented. The conclusions are that without an outlet orifice, the hydraulic system will not contribute with any damping at all. Furthermore, large dead volumes in the cylinder will increase the damping, but at the expense of the system’s efficiency.

  • 20.
    B M, Shiva Kumar
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems.
    Ramanujam, kathiravan
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems.
    Thermal Simulation of Hybrid Drive System2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Safety, performance and driving comforts are given high importance while developing modern day cars. All-Wheel Drive vehicles are exactly designed to fulfill such requirements. In modern times, human concern towards depleting fossil fuels and cognizance of ecological issues have led to new innovations in the field of Automotive engineering. One such outcome of the above process is the birth of electrical hybrid vehicles. The product under investigation is a combination of all wheel drive and hybrid system. A superior fuel economy can be achieved using hybrid system and optimized vehicle dynamic forces are accomplished by torque vectoring action which in turn provides All-Wheel Drive capabilities.

    Heat generation is inevitable whenever there is a conversion of energy from one form into another. In this master thesis investigation, a thermal simulation model for the product is built using 1D simulation tool AMESim and validation is done against the vehicle driving test data. AMESim tool was chosen for its proven track record related to vehicle thermal management. The vehicle CAN data are handled in MATLAB. In a nutshell, Simulation model accounts for heat generation sources, oil flow paths, power loss modeling and heat transfer phenomena.

    The final simulation model should be able to predict the transient temperature evolution in the rear drive when the speed and torque of motor is supplied as input. This simulation model can efficiently predict temperature patterns at various locations such as casing, motor inner parts as well as coolant at different places. Various driving cases were tried as input including harsh (high torque, low speed) ones. Simulation models like this helps Engineers in trying out new cooling strategies. Flow path optimization, flow rate, convection area, coolant pump controlling etc are the few variables worth mentioning in this regard.

  • 21.
    Baer, Katharina
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Simulation-Based Optimization of a Series Hydraulic Hybrid Vehicle2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hybrid transmissions are characterized by their utilization of more than one form of energy storage. They have the potential to help reduce overall fuel consumption and vehicle emissions by providing the possibility of brake energy recuperation and prime mover operation management. Electric hybrids and electric vehicle drives are nowadays ubiquitous, and mechanical energy storage in flywheel has been investigated in the past. The use of fluid power technology with a combustion engine has also been investigated since the late 1970s, and is frequently revisited.

    Hydraulic hybridization is especially attractive for heavy vehicles with frequent braking and acceleration which benefit most from fluid power components’ high power density, typically busses, delivery or refuse vehicles, and vehicles with existing hydraulic circuits and transmissions, such as forest and construction machinery, but have been considered for smaller vehicles as well.

    Due to the characteristic discharge profile of hydraulic energy storage, special attention needs to be paid to control aspects in the design process to guarantee drivability of the vehicle. In this respect, simulation models can be of use in early design process stages for cheaper and faster evaluation of concepts and designs than physical experiments and prototyping, and to generate better understanding of the system studied. Engineering optimization aids in the systematic exploration of a given design space, to determine limits and potentials, evaluate trade-offs and potentially find unexpected solutions. In the optimization of a hydraulic hybrid transmission, the integration of component and controller design is of importance, and different strategies (sequential, iterative, bi-level and simultaneous approaches) are conceivable, with varying consequences for the implementation.

    This thesis establishes a simulation-based optimization framework for a hydraulic hybrid transmission with series architecture. Component and control parameter optimization are addressed simultaneously, using a rule-based supervisory control strategy. The forward-facing dynamic simulation model at the centre of the framework is built in Hopsan, a multi-disciplinary open-source tool developed at Linköping University. The optimization is set up and conducted for an example application of an on-road light-duty truck over standard drive cycles. Both results from these experiments as well as the framework itself are studied and evaluated. Relevant design aspects, such as explicit design relations to be considered and performance requirements for more robust design, are identified and addressed, and the optimization problem is analysed with regard to algorithm performance and problem formulation. The final result is an optimization framework that can be adjusted for further in-depth studies, for example through the inclusion of additional components or optimization objectives, and extendable for comparative analysis of different topologies, applications and problem formulations.  

    List of papers
    1. System Parameter Study for a Light-Weight Series Hydraulic Hybrid Vehicle
    Open this publication in new window or tab >>System Parameter Study for a Light-Weight Series Hydraulic Hybrid Vehicle
    2014 (English)In: PROCEEDINGS OF THE 8TH FPNI PH.D SYMPOSIUM ON FLUID POWER, 2014, ASME Press, 2014, p. V001T03A004-Conference paper, Published paper (Refereed)
    Abstract [en]

    Amongst the hybrid vehicle propulsion solutions aiming to improve fuel efficiency, hybrid electric solutions currently receive most attention, especially on the market. However, hydraulic hybrids are an interesting alternative, especially for heavier vehicles due to higher power density which is beneficial if higher masses are moved. As a step towards a comprehensive design framework to compare several possible hydraulic hybrid architectures for a specified application and usage profile, the model of a series hydraulic hybrid vehicle was previously introduced and initially studied concerning component sizing for an exemplary light-duty vehicle in urban traffic. The vehicle is modeled in the Hopsan simulation tool. A comparably straight-forward engine management is used for the vehicle control; both pump and engine controls are based on the hydraulic accumulator’s state-of-charge. The model is developed further with respect to the accumulator component model. Based on that, the influence of several system and component parameters, such as maximum system pressure and engine characteristics, as well as controller parameters on the vehicle’s performance is analyzed. The goal is to allow for more understanding of the system’s characteristics to facilitate future optimization of the system.

    Place, publisher, year, edition, pages
    ASME Press, 2014
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-114212 (URN)10.1115/FPNI2014-7840 (DOI)000359389400029 ()978-0-7918-4582-0 (ISBN)
    Conference
    8th FPNI Ph.D Symposium on Fluid Power, Lappeenranta, Finland, June 11–13, 2014
    Available from: 2015-02-13 Created: 2015-02-13 Last updated: 2018-03-09
    2. Design Study and Parameter Optimization for a Light-Weight Series Hydraulic Hybrid Vehicle
    Open this publication in new window or tab >>Design Study and Parameter Optimization for a Light-Weight Series Hydraulic Hybrid Vehicle
    2015 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Hydraulic hybrid drives are one potential way of improving the fuel efficiency of vehicles, including the possi-bility of recuperating braking energy in a hydraulic accumulator. The high power density of fluid power is mainly advantageous for heavy vehicles, or duty cycles characterized with frequent braking and acceleration. For smaller vehicles, hydraulic hybrid drives are thus most interesting under urban and suburban driving conditions. Amongst the existing architectures, the series hydraulic hybrid offers the advantage of operating the internal combustion engine independently of the vehicle speed, at the cost of a less efficient transmission path than a purely mechanical one. Previously, a series hydraulics hybrid light-duty vehicle was modelled in the transmission-line modelling (TLM)-based simulation software Hopsan from the division of Fluid and Mechatronic Systems (Flumes) at Linköping University. This paper studies through simulation-based optimi-zation how the fuel-optimal vehicle design is affected by various mixes of urban and suburban driving requirements. Both the system’s hardware and the parameters of a basic control strategy are considered. The results show quite similar designs for most performance requirements combinations, and can be the base for further studies addressing additional requirements, conditions and objectives.

    Series
    Scandinavian International Conference on Fluid Power (SICFP), ISSN 2342-2726
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-122004 (URN)
    Conference
    14th Scandinavian International Conference on Fluid Power (SICFP'15), Tampere, Finland
    Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2018-03-09
    3. Aspects of Parameter Sensitivity for Series Hydraulic Hybrid Light-Weight Duty Vehicle Design
    Open this publication in new window or tab >>Aspects of Parameter Sensitivity for Series Hydraulic Hybrid Light-Weight Duty Vehicle Design
    2016 (English)In: Proceedings of the 9th FPNI Ph.D. Symposium on Fluid Power (FPNI2016), American Society of Mechanical Engineers , 2016, article id V001T01A041Conference paper, Published paper (Refereed)
    Abstract [en]

    Hybridization of a vehicle’s drivetrain can in principle help to improve its energy efficiency by allowing for recuperation of kinetic energy and modulating the engine’s load. How well this can be realized depends on appropriate sizing and control of the additional components. The system is typically designed sequentially, with the hardware setup preceding the development and tuning of advanced controller architectures. Taking an alternative approach, component sizing and controller tuning can be addressed simultaneously through simulation-based optimization.

    The results of such optimizations, especially with standard algorithms with continuous design variable ranges, can however be difficult to realize, considering for example limitations in available components. Furthermore, drive-cycle based optimizations are prone to cycle-beating. This paper examines the results of such simulation-based optimization for a series hydraulic hybrid vehicle in terms of sensitivity to variations in design parameters, system parameters and drive cycle variations. Additional relevant aspects concerning the definition of the optimization problem are pointed out.

    Place, publisher, year, edition, pages
    American Society of Mechanical Engineers, 2016
    Keywords
    Weight (Mass), Automotive design, Cycles, Optimization, Control equipment, Simulation, Design, Hybrid electric vehicles, Hardware, Stress
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-135737 (URN)10.1115/FPNI2016-1567 (DOI)978-0-7918-5047-3 (ISBN)
    Conference
    9th FPNI Ph.D. Symposium on Fluid Power, Florianópolis, SC, Brazil, October 26–28, 2016
    Available from: 2017-03-17 Created: 2017-03-17 Last updated: 2018-03-09
    4. Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle
    Open this publication in new window or tab >>Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle
    2018 (English)In: International Journal of Fluid Power, ISSN 1439-9776Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Hybridisation of hydraulic drivetrains offers the potential of efficiency improvement for on – and off-road applications. To realise the advantages, a carefully designed system and corresponding control strategy are required, which are commonly obtained through a sequential design process. Addressing component selection and control parameterisation simultaneously through simulation-based optimisation allows for exploration of a large design space as well as design relations and trade-offs, and their evaluation in dynamic conditions which exist in real driving scenarios. In this paper, the optimisation framework for a hydraulic hybrid vehicle is introduced, including the simulation model for a series hybrid architecture and component scaling considerations impacting the system’s performance. A number of optimisation experiments for an on-road light-duty vehicle, focused on standard-drive-cycle-performance, illustrate the impact of the problem formulation on the final design and thus the complexity of the design problem. The designs found demonstrate both the potential of energy storage in series hybrids, via an energy balance diagram, as well as some challenges. The framework presented here provides a base for systematic evaluation of design alternatives and problem formulation aspects.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2018
    Keywords
    Simulation-based optimization, hydraulic hybrid vehicle, series hybrid, simultaneous design and control optimization, Hopsan
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-152353 (URN)10.1080/14399776.2018.1527122 (DOI)2-s2.0-85055674140 (Scopus ID)
    Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2018-11-23Bibliographically approved
  • 22.
    Baer, Katharina
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ericson, Liselott
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Aspects of Parameter Sensitivity for Series Hydraulic Hybrid Light-Weight Duty Vehicle Design2016In: Proceedings of the 9th FPNI Ph.D. Symposium on Fluid Power (FPNI2016), American Society of Mechanical Engineers , 2016, article id V001T01A041Conference paper (Refereed)
    Abstract [en]

    Hybridization of a vehicle’s drivetrain can in principle help to improve its energy efficiency by allowing for recuperation of kinetic energy and modulating the engine’s load. How well this can be realized depends on appropriate sizing and control of the additional components. The system is typically designed sequentially, with the hardware setup preceding the development and tuning of advanced controller architectures. Taking an alternative approach, component sizing and controller tuning can be addressed simultaneously through simulation-based optimization.

    The results of such optimizations, especially with standard algorithms with continuous design variable ranges, can however be difficult to realize, considering for example limitations in available components. Furthermore, drive-cycle based optimizations are prone to cycle-beating. This paper examines the results of such simulation-based optimization for a series hydraulic hybrid vehicle in terms of sensitivity to variations in design parameters, system parameters and drive cycle variations. Additional relevant aspects concerning the definition of the optimization problem are pointed out.

  • 23.
    Baer, Katharina
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ericson, Liselott
    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.
    Component Sizing Study for a Light-Duty Series Hydraulic Hybrid Vehicle in Urban Drive Cycles2013Conference paper (Refereed)
    Abstract [en]

    With the focus on energy efficiency for many different kinds of vehicle applications,hybridization is considered a possible solution to reduce fuel consumption. While hybrid electric concepts are already available for passenger vehicles, and also considered for heavier applications, hybrid hydraulic alternatives have been mainly limited to the latter, which benefit most from the higher power density available. To study the different hybrid architectures and applications, a modeling framework for the system design is developed using the simulation tool Hopsan from Linköping University.  Previously,  the  model  of  a  series  hydraulic  hybrid  vehicle  was introduced, a light-duty vehicle simulated over two standard urban drive cycles, and its potential for further work established. In this paper, the model is extended by including a simple combustion engine power management to provide for more realistic propulsion of the hydraulic drivetrain, showing the potential to operate a series hydraulic hybrid vehicle’s engine in more efficient regions. Additionally, the design is studied concerning the effects of a variation of key component sizes on the accuracy and energy efficiency objectives. Instead of subjecting the system to (multi- objective) optimization, at this stage the individual component’s influence is studied, and the objectives are dealt with separately from each other to eliminate the need for compromise   between   them,   both   to   gain a better understanding of the interdependencies.

  • 24.
    Baer, Katharina
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ericson, Liselott
    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, Faculty of Science & Engineering.
    Design Study and Parameter Optimization for a Light-Weight Series Hydraulic Hybrid Vehicle2015Conference paper (Refereed)
    Abstract [en]

    Hydraulic hybrid drives are one potential way of improving the fuel efficiency of vehicles, including the possi-bility of recuperating braking energy in a hydraulic accumulator. The high power density of fluid power is mainly advantageous for heavy vehicles, or duty cycles characterized with frequent braking and acceleration. For smaller vehicles, hydraulic hybrid drives are thus most interesting under urban and suburban driving conditions. Amongst the existing architectures, the series hydraulic hybrid offers the advantage of operating the internal combustion engine independently of the vehicle speed, at the cost of a less efficient transmission path than a purely mechanical one. Previously, a series hydraulics hybrid light-duty vehicle was modelled in the transmission-line modelling (TLM)-based simulation software Hopsan from the division of Fluid and Mechatronic Systems (Flumes) at Linköping University. This paper studies through simulation-based optimi-zation how the fuel-optimal vehicle design is affected by various mixes of urban and suburban driving requirements. Both the system’s hardware and the parameters of a basic control strategy are considered. The results show quite similar designs for most performance requirements combinations, and can be the base for further studies addressing additional requirements, conditions and objectives.

  • 25.
    Baer, Katharina
    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.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle2018In: International Journal of Fluid Power, ISSN 1439-9776Article in journal (Refereed)
    Abstract [en]

    Hybridisation of hydraulic drivetrains offers the potential of efficiency improvement for on – and off-road applications. To realise the advantages, a carefully designed system and corresponding control strategy are required, which are commonly obtained through a sequential design process. Addressing component selection and control parameterisation simultaneously through simulation-based optimisation allows for exploration of a large design space as well as design relations and trade-offs, and their evaluation in dynamic conditions which exist in real driving scenarios. In this paper, the optimisation framework for a hydraulic hybrid vehicle is introduced, including the simulation model for a series hybrid architecture and component scaling considerations impacting the system’s performance. A number of optimisation experiments for an on-road light-duty vehicle, focused on standard-drive-cycle-performance, illustrate the impact of the problem formulation on the final design and thus the complexity of the design problem. The designs found demonstrate both the potential of energy storage in series hybrids, via an energy balance diagram, as well as some challenges. The framework presented here provides a base for systematic evaluation of design alternatives and problem formulation aspects.

  • 26.
    Baer, Katharina
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ericson, Liselott
    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.
    Modeling of a Series Hybrid Hydraulic Drivetrain for a Light-Duty Vehicle in Hopsan2013In: Conference proceedings: 13th Scandinavian International Conference on Fluid Power / [ed] Petter Krus, Magnus Sethson, Liselott Ericson, Linköping, Sweden: Linköping University Electronic Press, 2013, p. 107-112Conference paper (Refereed)
    Abstract [en]

    Hydraulic hybrids continue to receive attention as a possible solution in the search for improved fuel economy for different vehicle types. This paper presents a model for a series hydraulic hybrid light-duty vehicle, developed in the Hopsan simulation tool of Linköping University’s Division of Fluid and Mechatronic Systems (Flumes). Focusing on the hydraulic transmission which employs a pump control based on the hydraulic accumulator’s state-of-charge (SoC), several simplifications were made, especially concerning mechanical components. Simulation over two urban standard cycles shows promising results concerning dynamic performance and energy recuperation potential, provided sufficient component sizing to compensate for the mechanical limitations. This paper lays the foundation for both a further refined model - suitable for optimizing the full drivetrain, including component sizing and controller parameterization - and the development of comparable models for parallel and power-split hybrid architectures.

  • 27.
    Baer, Katharina
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Ericson, Liselott
    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.
    System Parameter Study for a Light-Weight Series Hydraulic Hybrid Vehicle2014In: PROCEEDINGS OF THE 8TH FPNI PH.D SYMPOSIUM ON FLUID POWER, 2014, ASME Press, 2014, p. V001T03A004-Conference paper (Refereed)
    Abstract [en]

    Amongst the hybrid vehicle propulsion solutions aiming to improve fuel efficiency, hybrid electric solutions currently receive most attention, especially on the market. However, hydraulic hybrids are an interesting alternative, especially for heavier vehicles due to higher power density which is beneficial if higher masses are moved. As a step towards a comprehensive design framework to compare several possible hydraulic hybrid architectures for a specified application and usage profile, the model of a series hydraulic hybrid vehicle was previously introduced and initially studied concerning component sizing for an exemplary light-duty vehicle in urban traffic. The vehicle is modeled in the Hopsan simulation tool. A comparably straight-forward engine management is used for the vehicle control; both pump and engine controls are based on the hydraulic accumulator’s state-of-charge. The model is developed further with respect to the accumulator component model. Based on that, the influence of several system and component parameters, such as maximum system pressure and engine characteristics, as well as controller parameters on the vehicle’s performance is analyzed. The goal is to allow for more understanding of the system’s characteristics to facilitate future optimization of the system.

  • 28.
    Blomgren, Niklas
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems.
    Decoupled Design of Auxiliary Systems for Internal Combustion Engines2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigated if decoupled design of the air intake and exhaust systems for four-stroke internal combustion engines is possible. Using the information found design guidelines were set up for the formula student team ELiTH Racing. The literature study revealed that the systems are not uncoupled, and the inuence of exhaust geometry on air intake behavior needed more thorough investigation. Experiments were designed, using a single cylinder engine with simple intake and exhaust geometries. The tests were attempted, but had to be abandoned due to time constraints. Successful tests would have yielded results in the form of pressure measurements, froma Prandtl-tube, in the air intake, and footage of smoke tests. As a secondary task the potential of computer simulations during the design process was investigated, which yielded a suggestion on how to set up a complete reasonable computational model of the systems. This also resulted in that the design guidelines included how to use computer simulations for the design process. Finally a few ways to expand this work are presented.

  • 29.
    Bodin, Erik
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Stenholm, Fanny
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Modelling & Control of a 3DOF Helicopter2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The scope of this report is the development of a mathematical model and a control system for a three degrees of freedom (3DOF) helicopter rig. This 3DOF-system offers a good simplification of a real world tandem helicopter for evaluating performanceof different automatic control principles.

    A mathematical model of the system is developed using free-body diagrams. This mathematical model is then linearized and a controller is developed by decoupling the system. Due to model imperfections external disturbances and similar effects integral action is added as well as feed-forward compensation to reduce nonlinear effects.

    After the controller has been decoupled the two different controllers are tuned. The Linear-Quadratic Regulator, described in section 3.6, is used for selectingstate-feedback gains. Due to the highly nonlinear nature of the system an Extended Kalman Filter is developed to estimate unmeasurable states.

    The model and controller is then implemented on the actual rig and evaluated. The results displayed that the elevation controller had good performance. The travel controller also showed good performance but not as good as the elevation controller.

    The main goal of this thesis was to develop a controller for the 3DOF helicopter system. The results clearly show that an LQR-controller is able to successfully control a system like this with decent performance characteristics despite the highly nonlinear system.

  • 30.
    Borg Bagge, Christian Borg Bagge
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology. -.
    Stability Criteria of Inline Axial Piston Pumps with Eccentric Control System2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis was to determine the stability criteria of an inline axialpiston pump with an eccentric control system. The hydrostatic/hydrodynamic bearings of the swash plate was inspected with model building and simulation as method. The general approach has been to regard the swash plate as stiff, leading to the hydrostatic friction between the swash plate and the pump house to be considered more or less constant. Recent research treat the swash plate as bendable which could lead to the swash plate bearings’ friction being replaced from mixed friction to a full contact interaction between the swash plate and the pump house, with an increased friction as result. This increase in friction is theorized to increase the stability ofthe pump by limiting the movement of the swash plate in comparison to the fully lubricated bearing. 

  • 31.
    Braun, Robert
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Distributed System Simulation Methods: For Model-Based Product Development2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Distributed system simulation can increase performance, re-usability and modularity in model-based product development. This thesis investigates four aspects of distributed simulation: multi-threaded simulations, simulation tool coupling, distributed equation solvers and parallel optimization algorithms.

    Multi-threaded simulation makes it possible to split up the workload over several processing units. This reduces simulation time, which can save both time and money during the product development cycle. The transmission line element method (TLM) is used to decouple models to independent sub-models.

    Different simulation tools are suitable for different problems. Tool coupling makes it possible to use the best suited tool for simulating each part of the whole product. Models from different tools can then be coupled into one aggregated simulation model. An emerging standard for tool coupling is the Functional Mock-up Interface (FMI). It is investigated how this can be used in conjunction with TLM.

    Equation-based object-oriented languages (EOOs) are becoming increasing popular. A logical approach is to let the equation solvers maintain the same structure that was used in the modelling process. Methods for achieving this using TLM and FMI are implemented and evaluated.

    In addition to parallel simulations, it is also possible to use parallel optimization algorithms. This introduces parallelism on several levels. For this reason, an algorithm for profile-based multi-level scheduling is proposed.

    List of papers
    1. Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    Open this publication in new window or tab >>Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    2016 (English)In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, no 10, p. 921-930Article in journal (Other academic) Published
    Abstract [en]

    By introducing physically motivated time delays, simulation models can be partitioned into decoupled independent sub-models. This enables parallel simulations on multi-core processors. An automatic algorithm is used for partitioning and running distributed system simulations. Methods for sorting and distributing components for good load balancing have been developed. Mathematical correctness during simulation is maintained by a busy-waiting thread synchronization algorithm. Independence between sub-models is achieved by using the transmission line element method. In contrast to the more commonly used centralized solvers, this method uses distributed solvers with physically motivated time delays, making simulations inherently parallel. Results show that simulation speed increases almost proportionally to the number of processor cores in the case of large models. However, overhead time costs mean that models need to be over a certain size to benefit from parallelization.

    Place, publisher, year, edition, pages
    Sage Publications, 2016
    Keywords
    Distributed Solvers, Parallelism, Problem Partitioning, Transmission Line Modelling, System Simulation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88024 (URN)10.1177/0037549716667243 (DOI)000385704300004 ()
    Note

    When first pubished online the status of this article was Manuscript.

    Funding agencies: ProViking research School; Swedish Foundation for Strategic Research (SSF)

    Available from: 2013-01-29 Created: 2013-01-29 Last updated: 2017-12-06Bibliographically approved
    2. Improved Scheduling Techniques for Parallel Distributed-Solver System Simulation
    Open this publication in new window or tab >>Improved Scheduling Techniques for Parallel Distributed-Solver System Simulation
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Shortening simulation time is an important step towards efficient simulation-based product development. A long-used method is to exploit physically motivated time delays to split up the model into distributed solvers. In this way, the use of a centralized sequential solver can be circumvented. For maximum simulation performance, however, an efficient scheduling technique is also required. Four task scheduling methods for distributed-solver simulations has been implemented and evaluated. Experiments indicate that the best choice largely depend on model size, load distribution and granularity. Lock-based barrier synchronization provides the highest speed-up for small models. A fork-join implementation, with implicit synchronization and work-stealing scheduling, works better for models with a large total workload. It is common that workload and load distribution of a simulation model varies during execution depending on the current state of the simulation. Three of the implemented schedulers support dynamic load balancing during execution. Results show that task-stealing is the most efficient method for the specific test model. A possible continuation of this work is an automatic selection of the best scheduling technique based on knowledge about model properties and available computer resources.

    Keywords
    System simulation, distributed solvers, parallelism, scheduling, transmission line element method
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-122749 (URN)
    Available from: 2015-11-19 Created: 2015-11-19 Last updated: 2015-11-19
    3. Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    Open this publication in new window or tab >>Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    2012 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    The demand for large-scale real-time simulations of fluid power systems is in-creasing, due to growing demands for added functionality. Real-time simulationscan be used in for example hardware-in-the-loop experiments and embeddedcontrol systems. In order to achieve real-time performance, it is often necessaryto use small or simplified models, reducing the usefulness and accuracy of theresults. This article proposes the use of transmission line modelling (TLM) forexploiting multi-core hardware in real-time and embedded systems. The charac-teristics of the TLM method are analysed to identify difficulties and possibilities.A method for how to parallelise TLM models is then presented. Subsequently, aprogramming interface for implementing the parallel models in the target systemsis introduced. Practical experiments show that the approach works and that themethod is applicable. So far, however, it has required great effort on the part ofthe engineer, both when it comes to programming, compiling and importing themodel into the target environments, although some attempts to automate the pro-cedure have been successful, reducing the level of complexity.

    Keywords
    Real-time simulation, Distributed modelling, Transmission line mod- elling, Parallel simulation, Multi-core, Model fidelity
    National Category
    Fluid Mechanics and Acoustics Other Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-76377 (URN)
    Conference
    8th International Fluid Power Conference, March 26-28, 2012, Dresden, Germany
    Available from: 2012-04-05 Created: 2012-04-05 Last updated: 2015-11-19Bibliographically approved
    4. Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation
    Open this publication in new window or tab >>Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation
    2016 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    A major concern in the forest industry is impact on the soil caused by forest machines during harvesting. A six-wheel pendulum arm forwarder is being developed. The new forwarder aims at reducing soil damage by an even pressure distribution and smooth torque control and thereby also improving the working environment. The suspension contains pendulum arms on each wheel controlled by a hydraulic load sensing system in combination with accumulator.

    A natural approach is to model each part of a system in the bestsuited software. In this case, the hydraulic system is modelled in the Hopsan simulation tool, while the vehicle mechanics is modelled in Adams. To understand the whole system it is necessary to simulate all subsystems together. An open standard for this is the Functional Mock-up Interface. This makes it possible to investigate the interaction between the hydraulic system and the multi-body mechanic model.

    This paper describes how different simulation tools can be combined to support the development process. The technique is applied to the forwarder’s pendulum suspension. Controllers for height and soil force are optimized to minimize soil damage and maximize comfort for the operator.

    Place, publisher, year, edition, pages
    ASME Press, 2016
    Keywords
    System simulation, distributed solvers, parallelism, scheduling, transmission line element method
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-122750 (URN)10.1115/FPMC2015-9588 (DOI)000373970500047 ()
    Conference
    ASME/BATH 2015 Symposium on Fluid Power and Motion Control, October 12-14, 2015, Chicago, USA
    Available from: 2015-11-19 Created: 2015-11-19 Last updated: 2017-12-20Bibliographically approved
    5. An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language
    Open this publication in new window or tab >>An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language
    2014 (English)In: Proceedings of the 6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools / [ed] David Broman & Peter Pepper, New York: Association for Computing Machinery (ACM), 2014, p. 57-64Conference paper, Published paper (Refereed)
    Abstract [en]

    The Modelica language offers an intuitive way to create object-oriented models. This makes it natural also to use an object-oriented solver, where each sub-model solves its own equations. Doing so is possible only if sub-models can be made independent from the rest of the model. One way to achieve this is to use distributed solvers by separating sub-models with transmission line elements. This offers robust and predictable simulations, simplified model debugging and natural parallelism. It also makes it possible to use different time steps and solver algorithms in different parts of the model to achieve an optimal trade-off between performance and accuracy. The suggested method has been implemented in the Hopsan simulation environment. Different modelling techniques for taking advantage of the distributed solver approach are explained. Finally, three example models are used to demonstrate the method.

    Place, publisher, year, edition, pages
    New York: Association for Computing Machinery (ACM), 2014
    Keywords
    distributed solvers, transmission line element method, Modelica, model generation
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-111478 (URN)10.1145/2666202.2666212 (DOI)978-1-4503-2953-8 (ISBN)
    Conference
    6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, Berlin, October 10, 2014
    Projects
    HiPO
    Funder
    Swedish Foundation for Strategic Research
    Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2015-11-19Bibliographically approved
    6. Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface
    Open this publication in new window or tab >>Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface
    2013 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper describes how models from different simulation tools can be connected and simulated on different processors by using the Functional Mockup Interface (FMI) and the transmission line element method (TLM). Interconnectivity between programs makes it possible to model each part of a complex system with the best suited tool, which will shorten the modelling time and increase the accuracy of the results. Because the system will be naturally partitioned, it is possible to identify weak links and replace them with transmission line elements, thereby introducing a controlled time delay. This makes the different parts of the system naturally independent, making it possible to simulate large aggregated system models with good performance on multi-core processors. The proposed method is demonstrated on an example model. A suggestion of an XML extension to the FMI standard for describing TLM ports is also presented.

    Keywords
    Functional Mockup Interface (FMI), Functional Mockup Unit (FMU), Transmission Line Element Method (TLM), Parallelism, Co-Simulation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-99870 (URN)
    Conference
    53rd SIMS conference on Simulation and Modelling, October 4-6, Reykjavik, Iceland
    Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2015-11-19Bibliographically approved
    7. Parallel Implementations of the Complex-RF Algorithm
    Open this publication in new window or tab >>Parallel Implementations of the Complex-RF Algorithm
    2017 (English)In: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273, Vol. 49, no 9, p. 1558-1572Article in journal (Refereed) Published
    Abstract [en]

    Even though direct-search optimization methods are more difficult to parallelize than population-based methods, there are many unexploited opportunities. Five methods for parallelizing the Complex-RF methods have been implemented and evaluated. Three methods are based on the unchanged original algorithm, while two require modifications. The methods have been tested on two test function and one real simulation model. An analysis of the algorithm has been performed. This provides a basis for parametrization of the parallel methods. Without changing the original algorithm, speed-up of 2.5-3 is achieved. With allowing modifications, a speed-up of up to 5 is obtained without significantly reducing the probability of finding the global minimum. Speed-up does not scale linear to the number of threads. When more threads are added, parallelization efficiency decreases. However, a comparison with a particle swarm method shows that Complex-RF performs better regardless of the number of threads, due to its fast convergence rate.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2017
    Keywords
    Parallel optimization, direct-search, simplex, Complex-RF
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-122751 (URN)10.1080/0305215X.2016.1260712 (DOI)000404810100006 ()
    Note

    The prevuous status of this article was Manuscript.

    Available from: 2015-11-19 Created: 2015-11-19 Last updated: 2017-08-09Bibliographically approved
    8. Job-Scheduling of Distributed Simulation-Based Optimization with Support for Multi-Level Parallelism
    Open this publication in new window or tab >>Job-Scheduling of Distributed Simulation-Based Optimization with Support for Multi-Level Parallelism
    2015 (English)In: Proceedings of the 56th Conference on Simulation and Modelling (SIMS 56): October, 7-9, 2015, Linköping University, Sweden, Linköping: Linköping University Electronic Press, 2015, p. 187-197Conference paper, Published paper (Refereed)
    Abstract [en]

    In many organizations, the utilization of available computer power is very low. If it could be harnessed for parallel simulation and optimization, valuable time could be saved. A framework monitoring available computer resources and running distributed simulations is proposed. Users build their models locally, and then let a job scheduler determine how the simulation work should be divided among remote computers providing simulation services. Typical applications include sensitivity analysis, co-simulation and design optimization. The latter is used to demonstrate the framework. Optimizations can be parallelized either across the algorithm or across the model. An algorithm for finding the optimal distribution of the different levels of parallelism is proposed. An initial implementation of the framework, using the Hopsan simulation tool, is presented. Three parallel optimization algorithms have been used to verify the method and a thorough examination of their parallel speed-up is included.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2015
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 119
    Keywords
    Job-scheduling, parallelism, distributed simulation, optimization
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-122752 (URN)10.3384/ecp15119187 (DOI)9789176859001 (ISBN)
    Conference
    The 56th Conference on Simulation and Modelling (SIMS 56), “Modelling, Simulation and Optimization”, Linköping, Sweden, 7-9 October 2015
    Available from: 2015-11-19 Created: 2015-11-19 Last updated: 2018-02-02Bibliographically approved
  • 32.
    Braun, Robert
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Multi-Threaded Distributed System Simulations: Using Bi-Lateral Delay Lines2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    As the speed increase of single-core processors keeps declining, it is important to adapt simulation software to take advantage of multi-core technology. There is a great need for simulating large-scale systems with good performance. This makes it possible to investigate how different parts of a system work together, without the need for expensive physical prototypes. For this to be useful, however, the simulations cannot take too long, because this would delay the design process. Some uses of simulation also put very high demands on simulation performance, such as real-time simulations, design optimization or Monte Carlo-based sensitivity analysis. Being able to quickly simulate large-scale models can save much time and money.

    The power required to cool a processor is proportional to the processor speed squared. It is therefore no longer profitable to keep increasing the speed. This is commonly referred to as the "power wall". Manufacturers of processors have instead begun to focus on building multi-core processors consisting of several cores working in parallel. Adapting program code to multi-core architectures constitutes a major challenge for software developers.

    Traditional simulation software uses centralized equation-system solvers, which by nature are hard to make parallel. By instead using distributed solvers, equations from different parts of the model can be solved simultaneously. For this to be effective, it is important to minimize overheadcosts and to make sure that the workload is evenly distributed over the processor cores.

    Dividing an equation system into several parts and solving them separately means that time delays will be introduced between the parts. If these occur in the right locations, this can be physically correct, since it also takes some time for information to propagate in physical systems. The transmission line  element method (TLM) constitutes an effective method for separating system models by introducing impedances between components, causing physically motivated time delays.

    Contributions in this thesis include parts of the development of the new generation of the Hopsan simulation tool, with support for TLM and distributed solvers. An automatic algorithm for partitioning models has been developed. A multi-threaded simulation algorithm using barrier synchronization has also been implemented.

    Measurements of simulation time confirm that the simulation time is decreased almost proportionally to the number of processor cores for large models. The decrease, however, is reduced if the cores are divided on different processors. This was expected, due to the communication delay for processors communicating over shared memory. Experiments on real-time systems with four cores show that a four times as large model can be simulated without losing real-time performance.

    The division into distributed solvers constitutes a sort of natural cosimulation. A future project could be to use this as a platform for linking different simulation tools together and simulating them with high performance. This would make it possible to model each part of the system in the most suitable tool, and then connect all parts into one large model.

    List of papers
    1. Next Generation Simulation Software using Transmission Line Elements
    Open this publication in new window or tab >>Next Generation Simulation Software using Transmission Line Elements
    Show others...
    2010 (English)In: Fluid Power and Motion Control / [ed] Dr D N Johnston and Professor A R Plummer, Centre for Power Transmission and Motion Control , 2010, p. 265-276Conference paper, Published paper (Refereed)
    Abstract [en]

    A suitable method for simulating large complex dynamic systems is represented by distributed modelling using transmission line elements. The method is applicable to all physical systems, such as mechanical, electrical and pneumatics, but is particularly well suited to simulate systems where wave propagation is an important issue, for instance hydraulic systems. By using this method, components can be numerically isolated from each other, which provide highly robust numerical properties. It also enables the use of multi-core architecture since a system model can be composed by distributed simulations of subsystems on different processor cores.

    Technologies based on transmission lines has successfully been implemented in the HOPSAN simulation package, develop at Linköping University. Currently, the next generation of HOPSAN is developed using an object-oriented approach. The work is focused on compatibility, execution speed and real-time simulation in order to facilitate hardware-in-the-loop applications. This paper presents the work progress and some possible features in the new version of the HOPSAN simulation package.

    Place, publisher, year, edition, pages
    Centre for Power Transmission and Motion Control, 2010
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-59661 (URN)978-1-86197-181-4 (ISBN)
    Conference
    Fluid Power and Motion Control, 15th-17th September, Bath, England, UK
    Projects
    HiPO
    Available from: 2010-11-08 Created: 2010-09-23 Last updated: 2016-05-27Bibliographically approved
    2. High Performance System Simulation Using Multiple Processor Cores
    Open this publication in new window or tab >>High Performance System Simulation Using Multiple Processor Cores
    2011 (English)In: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11 / [ed] Harri Sairiala & Kari T. Koskinen, 2011Conference paper, Published paper (Refereed)
    Abstract [en]

    Future research and development will depend on high-speed simulations, especially for large and complex systems. Rapid prototyping, optimization and real-time simulations require  simulation tools that can take full advantage of  computer hardware.  Recent developments  in the computer market indicate  a change in focus from increasing the speed of processor cores towards increasing the number of cores in each processor. HOPSAN is a simulation tool for fluid power and mechatronics, developed at Linköping University. It  is based upon the transmission line  modeling  (TLM)  technique. This method is very suitable for taking advantage of multi-core  processors.  This paper presents  the  implementation  of multi-core support in the next generation of HOPSAN. The concept is to divide the  model  into equally sized  groups of  independent components,  to make it possible to  simulate  them  in separate threads. Reducing overhead costs and finding an effective sorting algorithm constitute  critical steps for maximizing the benefits.  Experimental results show  a significant reduction in simulation time. Improvement of algorithms in combination with a continuous increase in the number of processor cores can potentially  lead to further  increases  in simulation performance. 

    Keywords
    Multi-core, simulation, transmission line element method, transmission line modelling, fluid power, system simulation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-68373 (URN)978-952-15-2517-9 (ISBN)978-952-15-2520-9 (ISBN)978-952-15-3273-3 (ISBN)
    Conference
    The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11, 18th–20th May, Tampere, Finland
    Available from: 2011-05-23 Created: 2011-05-23 Last updated: 2016-04-07
    3. Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    Open this publication in new window or tab >>Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    2012 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    The demand for large-scale real-time simulations of fluid power systems is in-creasing, due to growing demands for added functionality. Real-time simulationscan be used in for example hardware-in-the-loop experiments and embeddedcontrol systems. In order to achieve real-time performance, it is often necessaryto use small or simplified models, reducing the usefulness and accuracy of theresults. This article proposes the use of transmission line modelling (TLM) forexploiting multi-core hardware in real-time and embedded systems. The charac-teristics of the TLM method are analysed to identify difficulties and possibilities.A method for how to parallelise TLM models is then presented. Subsequently, aprogramming interface for implementing the parallel models in the target systemsis introduced. Practical experiments show that the approach works and that themethod is applicable. So far, however, it has required great effort on the part ofthe engineer, both when it comes to programming, compiling and importing themodel into the target environments, although some attempts to automate the pro-cedure have been successful, reducing the level of complexity.

    Keywords
    Real-time simulation, Distributed modelling, Transmission line mod- elling, Parallel simulation, Multi-core, Model fidelity
    National Category
    Fluid Mechanics and Acoustics Other Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-76377 (URN)
    Conference
    8th International Fluid Power Conference, March 26-28, 2012, Dresden, Germany
    Available from: 2012-04-05 Created: 2012-04-05 Last updated: 2015-11-19Bibliographically approved
    4. Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    Open this publication in new window or tab >>Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    2016 (English)In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, no 10, p. 921-930Article in journal (Other academic) Published
    Abstract [en]

    By introducing physically motivated time delays, simulation models can be partitioned into decoupled independent sub-models. This enables parallel simulations on multi-core processors. An automatic algorithm is used for partitioning and running distributed system simulations. Methods for sorting and distributing components for good load balancing have been developed. Mathematical correctness during simulation is maintained by a busy-waiting thread synchronization algorithm. Independence between sub-models is achieved by using the transmission line element method. In contrast to the more commonly used centralized solvers, this method uses distributed solvers with physically motivated time delays, making simulations inherently parallel. Results show that simulation speed increases almost proportionally to the number of processor cores in the case of large models. However, overhead time costs mean that models need to be over a certain size to benefit from parallelization.

    Place, publisher, year, edition, pages
    Sage Publications, 2016
    Keywords
    Distributed Solvers, Parallelism, Problem Partitioning, Transmission Line Modelling, System Simulation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88024 (URN)10.1177/0037549716667243 (DOI)000385704300004 ()
    Note

    When first pubished online the status of this article was Manuscript.

    Funding agencies: ProViking research School; Swedish Foundation for Strategic Research (SSF)

    Available from: 2013-01-29 Created: 2013-01-29 Last updated: 2017-12-06Bibliographically approved
  • 33.
    Braun, Robert
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Asghar, Adeel
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Pop, Adrian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fritzson, Dag
    SKF Group Technology, AB SKF.
    An Open-Source Framework for Efficient Co-simulation of Fluid Power Systems2017In: Proceedings of 15th Scandinavian International Conference on Fluid Power, SICFP’17, Linköping: Linköping University Electronic Press, 2017, Vol. 144, p. 393-400Conference paper (Refereed)
    Abstract [en]

    Simulation of fluid power systems typically requires models from multiple disciplines.Achieving accurate load dynamics for a system with complex geometry, for example, mayrequire both a 1D model of the hydraulic circuit and a 3D multi-body model. However, mostsimulation tools are limited to a single discipline. A solution to these kinds of problems isco-simulation, where different tools are coupled and simulated together. Co-simulation canprovide increased accuracy, improved modularity and facilitated collaboration between dif-ferent organizations. Unfortunately, tool coupling typically requires tedious and error-pronemanual work. It may also introduce numerical problems. For these reasons, co-simulation isoften avoided as long as possible. These problems have been addressed by the developmentof an open-source framework for asynchronous co-simulation. Simulation tools can be inter-connected through a stand-alone master simulation tool. An extensive range of tools is alsosupported via the Functional Mockup Interface standard. A graphical user interface has beenimplemented in the OpenModelica Connection Editor. System models can be created andedited from both a schematic view and a 3D view. Numerical robustness is enforced by theuse of transmission line modelling. A minimalistic programming interface consisting of onlytwo functions is used. An example model consisting of a hydraulic crane with two arms, twoactuators and a hanging load is used to verify the framework. The composite model consistsof nine multi-body models, one hydraulic system model and a controller. It is shown thatmodels from various simulation tools can be replaced with a minimal amount of user input.

  • 34.
    Braun, Robert
    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.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation2016Conference paper (Refereed)
    Abstract [en]

    A major concern in the forest industry is impact on the soil caused by forest machines during harvesting. A six-wheel pendulum arm forwarder is being developed. The new forwarder aims at reducing soil damage by an even pressure distribution and smooth torque control and thereby also improving the working environment. The suspension contains pendulum arms on each wheel controlled by a hydraulic load sensing system in combination with accumulator.

    A natural approach is to model each part of a system in the bestsuited software. In this case, the hydraulic system is modelled in the Hopsan simulation tool, while the vehicle mechanics is modelled in Adams. To understand the whole system it is necessary to simulate all subsystems together. An open standard for this is the Functional Mock-up Interface. This makes it possible to investigate the interaction between the hydraulic system and the multi-body mechanic model.

    This paper describes how different simulation tools can be combined to support the development process. The technique is applied to the forwarder’s pendulum suspension. Controllers for height and soil force are optimized to minimize soil damage and maximize comfort for the operator.

  • 35.
    Braun, Robert
    et al.
    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.
    An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language2014In: Proceedings of the 6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools / [ed] David Broman & Peter Pepper, New York: Association for Computing Machinery (ACM), 2014, p. 57-64Conference paper (Refereed)
    Abstract [en]

    The Modelica language offers an intuitive way to create object-oriented models. This makes it natural also to use an object-oriented solver, where each sub-model solves its own equations. Doing so is possible only if sub-models can be made independent from the rest of the model. One way to achieve this is to use distributed solvers by separating sub-models with transmission line elements. This offers robust and predictable simulations, simplified model debugging and natural parallelism. It also makes it possible to use different time steps and solver algorithms in different parts of the model to achieve an optimal trade-off between performance and accuracy. The suggested method has been implemented in the Hopsan simulation environment. Different modelling techniques for taking advantage of the distributed solver approach are explained. Finally, three example models are used to demonstrate the method.

  • 36.
    Braun, Robert
    et al.
    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.
    Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method2016In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, no 10, p. 921-930Article in journal (Other academic)
    Abstract [en]

    By introducing physically motivated time delays, simulation models can be partitioned into decoupled independent sub-models. This enables parallel simulations on multi-core processors. An automatic algorithm is used for partitioning and running distributed system simulations. Methods for sorting and distributing components for good load balancing have been developed. Mathematical correctness during simulation is maintained by a busy-waiting thread synchronization algorithm. Independence between sub-models is achieved by using the transmission line element method. In contrast to the more commonly used centralized solvers, this method uses distributed solvers with physically motivated time delays, making simulations inherently parallel. Results show that simulation speed increases almost proportionally to the number of processor cores in the case of large models. However, overhead time costs mean that models need to be over a certain size to benefit from parallelization.

  • 37.
    Braun, Robert
    et al.
    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.
    Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements2012Conference paper (Refereed)
    Abstract [en]

    The demand for large-scale real-time simulations of fluid power systems is in-creasing, due to growing demands for added functionality. Real-time simulationscan be used in for example hardware-in-the-loop experiments and embeddedcontrol systems. In order to achieve real-time performance, it is often necessaryto use small or simplified models, reducing the usefulness and accuracy of theresults. This article proposes the use of transmission line modelling (TLM) forexploiting multi-core hardware in real-time and embedded systems. The charac-teristics of the TLM method are analysed to identify difficulties and possibilities.A method for how to parallelise TLM models is then presented. Subsequently, aprogramming interface for implementing the parallel models in the target systemsis introduced. Practical experiments show that the approach works and that themethod is applicable. So far, however, it has required great effort on the part ofthe engineer, both when it comes to programming, compiling and importing themodel into the target environments, although some attempts to automate the pro-cedure have been successful, reducing the level of complexity.

  • 38.
    Braun, Robert
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Parallel Implementations of the Complex-RF Algorithm2017In: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273, Vol. 49, no 9, p. 1558-1572Article in journal (Refereed)
    Abstract [en]

    Even though direct-search optimization methods are more difficult to parallelize than population-based methods, there are many unexploited opportunities. Five methods for parallelizing the Complex-RF methods have been implemented and evaluated. Three methods are based on the unchanged original algorithm, while two require modifications. The methods have been tested on two test function and one real simulation model. An analysis of the algorithm has been performed. This provides a basis for parametrization of the parallel methods. Without changing the original algorithm, speed-up of 2.5-3 is achieved. With allowing modifications, a speed-up of up to 5 is obtained without significantly reducing the probability of finding the global minimum. Speed-up does not scale linear to the number of threads. When more threads are added, parallelization efficiency decreases. However, a comparison with a particle swarm method shows that Complex-RF performs better regardless of the number of threads, due to its fast convergence rate.

  • 39.
    Braun, Robert
    et al.
    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.
    Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface2013Conference paper (Refereed)
    Abstract [en]

    This paper describes how models from different simulation tools can be connected and simulated on different processors by using the Functional Mockup Interface (FMI) and the transmission line element method (TLM). Interconnectivity between programs makes it possible to model each part of a complex system with the best suited tool, which will shorten the modelling time and increase the accuracy of the results. Because the system will be naturally partitioned, it is possible to identify weak links and replace them with transmission line elements, thereby introducing a controlled time delay. This makes the different parts of the system naturally independent, making it possible to simulate large aggregated system models with good performance on multi-core processors. The proposed method is demonstrated on an example model. A suggestion of an XML extension to the FMI standard for describing TLM ports is also presented.

  • 40.
    Braun, Robert
    et al.
    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.
    Towards A Parallel Distributed Equation-Based Simulation Environment2012In: 53rd SIMS Conference on Simulation and Modelling, 2012Conference paper (Refereed)
    Abstract [en]

    Distributed solvers provide several benefits, such as linear scalability and good numerical robustness. By separating components with transmission line elements, simulations can be run in parallel on multi-core processors. At the same time, equation-based modelling offers an intuitive way of writing models. This paper presents an algorithm for generating distributed models from Modelica code using bilinear transform. This also enables hard limitations on variables and their derivatives. The generated Jacobian is linearised and solved using LU-decomposition. The algorithm is implemented in the Hopsan simulation tool. Equations are transformed and differentiated by using the SymPy package for symbolic mathematics. An example model is created andverified against a reference model. Simulation results are similar, but the equation-based model is four to five times slower. Further optimisation of the algorithm is thus required. The future aim is to develop a distributed simulation environment with integrated support for equation-based modelling.

  • 41.
    Braun, Robert
    et al.
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Nordin, Peter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, The Institute of Technology.
    Eriksson, Björn
    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.
    High Performance System Simulation Using Multiple Processor Cores2011In: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11 / [ed] Harri Sairiala & Kari T. Koskinen, 2011Conference paper (Refereed)
    Abstract [en]

    Future research and development will depend on high-speed simulations, especially for large and complex systems. Rapid prototyping, optimization and real-time simulations require  simulation tools that can take full advantage of  computer hardware.  Recent developments  in the computer market indicate  a change in focus from increasing the speed of processor cores towards increasing the number of cores in each processor. HOPSAN is a simulation tool for fluid power and mechatronics, developed at Linköping University. It  is based upon the transmission line  modeling  (TLM)  technique. This method is very suitable for taking advantage of multi-core  processors.  This paper presents  the  implementation  of multi-core support in the next generation of HOPSAN. The concept is to divide the  model  into equally sized  groups of  independent components,  to make it possible to  simulate  them  in separate threads. Reducing overhead costs and finding an effective sorting algorithm constitute  critical steps for maximizing the benefits.  Experimental results show  a significant reduction in simulation time. Improvement of algorithms in combination with a continuous increase in the number of processor cores can potentially  lead to further  increases  in simulation performance.