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  • 1.
    Axin, Mikael
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Dell'Amico, Alessandro
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Björn
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Pettersson, Karl
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Staack, Ingo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik. Linköpings universitet, Tekniska högskolan.
    Next Generation Simulation Software using Transmission Line Elements2010Inngår i: Fluid Power and Motion Control / [ed] Dr D N Johnston and Professor A R Plummer, Centre for Power Transmission and Motion Control , 2010, s. 265-276Konferansepaper (Fagfellevurdert)
    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.

  • 2.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Distributed System Simulation Methods: For Model-Based Product Development2015Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

    Delarbeid
    1. Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    Åpne denne publikasjonen i ny fane eller vindu >>Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    2016 (engelsk)Inngår i: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, nr 10, s. 921-930Artikkel i tidsskrift (Annet vitenskapelig) 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.

    sted, utgiver, år, opplag, sider
    Sage Publications, 2016
    Emneord
    Distributed Solvers, Parallelism, Problem Partitioning, Transmission Line Modelling, System Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88024 (URN)10.1177/0037549716667243 (DOI)000385704300004 ()
    Merknad

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

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

    Tilgjengelig fra: 2013-01-29 Laget: 2013-01-29 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    2. Improved Scheduling Techniques for Parallel Distributed-Solver System Simulation
    Åpne denne publikasjonen i ny fane eller vindu >>Improved Scheduling Techniques for Parallel Distributed-Solver System Simulation
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    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.

    Emneord
    System simulation, distributed solvers, parallelism, scheduling, transmission line element method
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122749 (URN)
    Tilgjengelig fra: 2015-11-19 Laget: 2015-11-19 Sist oppdatert: 2015-11-19
    3. Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    Åpne denne publikasjonen i ny fane eller vindu >>Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    2012 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    Emneord
    Real-time simulation, Distributed modelling, Transmission line mod- elling, Parallel simulation, Multi-core, Model fidelity
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-76377 (URN)
    Konferanse
    8th International Fluid Power Conference, March 26-28, 2012, Dresden, Germany
    Tilgjengelig fra: 2012-04-05 Laget: 2012-04-05 Sist oppdatert: 2015-11-19bibliografisk kontrollert
    4. Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation
    Åpne denne publikasjonen i ny fane eller vindu >>Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation
    2016 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    sted, utgiver, år, opplag, sider
    ASME Press, 2016
    Emneord
    System simulation, distributed solvers, parallelism, scheduling, transmission line element method
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122750 (URN)10.1115/FPMC2015-9588 (DOI)000373970500047 ()
    Konferanse
    ASME/BATH 2015 Symposium on Fluid Power and Motion Control, October 12-14, 2015, Chicago, USA
    Tilgjengelig fra: 2015-11-19 Laget: 2015-11-19 Sist oppdatert: 2017-12-20bibliografisk kontrollert
    5. An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language
    Åpne denne publikasjonen i ny fane eller vindu >>An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language
    2014 (engelsk)Inngår i: 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, s. 57-64Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    sted, utgiver, år, opplag, sider
    New York: Association for Computing Machinery (ACM), 2014
    Emneord
    distributed solvers, transmission line element method, Modelica, model generation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-111478 (URN)10.1145/2666202.2666212 (DOI)978-1-4503-2953-8 (ISBN)
    Konferanse
    6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, Berlin, October 10, 2014
    Prosjekter
    HiPO
    Forskningsfinansiär
    Swedish Foundation for Strategic Research
    Tilgjengelig fra: 2014-10-17 Laget: 2014-10-17 Sist oppdatert: 2015-11-19bibliografisk kontrollert
    6. Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface
    Åpne denne publikasjonen i ny fane eller vindu >>Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface
    2013 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    Emneord
    Functional Mockup Interface (FMI), Functional Mockup Unit (FMU), Transmission Line Element Method (TLM), Parallelism, Co-Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-99870 (URN)
    Konferanse
    53rd SIMS conference on Simulation and Modelling, October 4-6, Reykjavik, Iceland
    Tilgjengelig fra: 2013-10-22 Laget: 2013-10-22 Sist oppdatert: 2015-11-19bibliografisk kontrollert
    7. Parallel Implementations of the Complex-RF Algorithm
    Åpne denne publikasjonen i ny fane eller vindu >>Parallel Implementations of the Complex-RF Algorithm
    2017 (engelsk)Inngår i: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273, Vol. 49, nr 9, s. 1558-1572Artikkel i tidsskrift (Fagfellevurdert) 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.

    sted, utgiver, år, opplag, sider
    Taylor & Francis, 2017
    Emneord
    Parallel optimization, direct-search, simplex, Complex-RF
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122751 (URN)10.1080/0305215X.2016.1260712 (DOI)000404810100006 ()
    Merknad

    The prevuous status of this article was Manuscript.

    Tilgjengelig fra: 2015-11-19 Laget: 2015-11-19 Sist oppdatert: 2017-08-09bibliografisk kontrollert
    8. Job-Scheduling of Distributed Simulation-Based Optimization with Support for Multi-Level Parallelism
    Åpne denne publikasjonen i ny fane eller vindu >>Job-Scheduling of Distributed Simulation-Based Optimization with Support for Multi-Level Parallelism
    2015 (engelsk)Inngår i: Proceedings of the 56th Conference on Simulation and Modelling (SIMS 56): October, 7-9, 2015, Linköping University, Sweden, Linköping: Linköping University Electronic Press, 2015, s. 187-197Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2015
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 119
    Emneord
    Job-scheduling, parallelism, distributed simulation, optimization
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122752 (URN)10.3384/ecp15119187 (DOI)9789176859001 (ISBN)
    Konferanse
    The 56th Conference on Simulation and Modelling (SIMS 56), “Modelling, Simulation and Optimization”, Linköping, Sweden, 7-9 October 2015
    Tilgjengelig fra: 2015-11-19 Laget: 2015-11-19 Sist oppdatert: 2018-02-02bibliografisk kontrollert
  • 3.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Multi-Threaded Distributed System Simulations: Using Bi-Lateral Delay Lines2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    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.

    Delarbeid
    1. Next Generation Simulation Software using Transmission Line Elements
    Åpne denne publikasjonen i ny fane eller vindu >>Next Generation Simulation Software using Transmission Line Elements
    Vise andre…
    2010 (engelsk)Inngår i: Fluid Power and Motion Control / [ed] Dr D N Johnston and Professor A R Plummer, Centre for Power Transmission and Motion Control , 2010, s. 265-276Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    sted, utgiver, år, opplag, sider
    Centre for Power Transmission and Motion Control, 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-59661 (URN)978-1-86197-181-4 (ISBN)
    Konferanse
    Fluid Power and Motion Control, 15th-17th September, Bath, England, UK
    Prosjekter
    HiPO
    Tilgjengelig fra: 2010-11-08 Laget: 2010-09-23 Sist oppdatert: 2016-05-27bibliografisk kontrollert
    2. High Performance System Simulation Using Multiple Processor Cores
    Åpne denne publikasjonen i ny fane eller vindu >>High Performance System Simulation Using Multiple Processor Cores
    2011 (engelsk)Inngår i: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11 / [ed] Harri Sairiala & Kari T. Koskinen, 2011Konferansepaper, Publicerat paper (Fagfellevurdert)
    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. 

    Emneord
    Multi-core, simulation, transmission line element method, transmission line modelling, fluid power, system simulation
    HSV kategori
    Identifikatorer
    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)
    Konferanse
    The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11, 18th–20th May, Tampere, Finland
    Tilgjengelig fra: 2011-05-23 Laget: 2011-05-23 Sist oppdatert: 2016-04-07
    3. Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    Åpne denne publikasjonen i ny fane eller vindu >>Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements
    2012 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    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.

    Emneord
    Real-time simulation, Distributed modelling, Transmission line mod- elling, Parallel simulation, Multi-core, Model fidelity
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-76377 (URN)
    Konferanse
    8th International Fluid Power Conference, March 26-28, 2012, Dresden, Germany
    Tilgjengelig fra: 2012-04-05 Laget: 2012-04-05 Sist oppdatert: 2015-11-19bibliografisk kontrollert
    4. Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    Åpne denne publikasjonen i ny fane eller vindu >>Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method
    2016 (engelsk)Inngår i: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, nr 10, s. 921-930Artikkel i tidsskrift (Annet vitenskapelig) 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.

    sted, utgiver, år, opplag, sider
    Sage Publications, 2016
    Emneord
    Distributed Solvers, Parallelism, Problem Partitioning, Transmission Line Modelling, System Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88024 (URN)10.1177/0037549716667243 (DOI)000385704300004 ()
    Merknad

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

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

    Tilgjengelig fra: 2013-01-29 Laget: 2013-01-29 Sist oppdatert: 2017-12-06bibliografisk kontrollert
  • 4.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Ericson, Liselott
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation2016Konferansepaper (Fagfellevurdert)
    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.

  • 5.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Hällqvist, Robert
    Fritzson, Dag
    TLM-Based Asynchronous Co-simulation with the Functional Mockup Interface2017Inngår i: Proceedings of the IUTAM Symposium on Solver-Coupling and Co-Simulation, Darmstadt, Germany, September 18-20, 2017 / [ed] Bernhard Schweizer, Switzerland, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Numerical stability is a key aspect in co-simulation of physical systems. Decoupling a system into independent sub-models will introduce time delays on interface variables. By utilizing physical time delays for decoupling, affecting the numerical stability can be avoided. This requires interpolation, to allow solvers to request input variables for the time slot where they are needed. The FMI for co-simulation standard does not support fine-grained interpolation using interpolation tables. Here, various modifications to the FMI standard are suggested for improved handling of interpolation. Mechanical and thermodynamic models are used to demonstrate the need for interpolation, as well as to provide an industrial context. It is shown that the suggested improvements are able to stabilize the otherwise unstable connections.

  • 6.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    An Explicit Method for Decoupled Distributed Solvers in an Equation-Based Modelling Language2014Inngår i: 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, s. 57-64Konferansepaper (Fagfellevurdert)
    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.

  • 7.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Multi-Threaded Distributed System Simulations Using the Transmission Line Element Method2016Inngår i: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, nr 10, s. 921-930Artikkel i tidsskrift (Annet vitenskapelig)
    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.

  • 8.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Multi-Threaded Real-Time Simulations of Fluid Power Systems Using Transmission Line Elements2012Konferansepaper (Fagfellevurdert)
    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.

  • 9.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Parallel Implementations of the Complex-RF Algorithm2017Inngår i: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273, Vol. 49, nr 9, s. 1558-1572Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Tool-Independent Distributed Simulations Using Transmission Line Elements And The Functional Mock-up Interface2013Konferansepaper (Fagfellevurdert)
    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.

  • 11.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Towards A Parallel Distributed Equation-Based Simulation Environment2012Inngår i: 53rd SIMS Conference on Simulation and Modelling, 2012Konferansepaper (Fagfellevurdert)
    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.

  • 12.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Eriksson, Björn
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    High Performance System Simulation Using Multiple Processor Cores2011Inngår i: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11 / [ed] Harri Sairiala & Kari T. Koskinen, 2011Konferansepaper (Fagfellevurdert)
    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. 

  • 13.
    Braun, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Improved Scheduling Techniques for Parallel Distributed-Solver System SimulationManuskript (preprint) (Annet vitenskapelig)
    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.

  • 14.
    Hällqvist, Robert
    et al.
    Systems Simulation and Concept Design, Saab Aeronautics, Linköping, Sweden.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Early Insights on FMI-based Co-Simulation of Aircraft Vehicle Systems2017Inngår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Eriksson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 262-270Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Modelling and Simulation is extensively used for aircraft vehicle system development at Saab Aeronautics in Linköping, Sweden. There is an increased desire to simulate interacting sub-systems together in order to reveal, and get an understanding of, the present cross-coupling effects early on in the development cycle of aircraft vehicle systems. The co-simulation methods implemented at Saab require a significant amount of manual effort, resulting in scarcely updated simulation models, and challenges associated with simulation model scalability, etc. The Functional Mock-up Interface (FMI) standard is identified as a possible enabler for efficient and standardized export and co-simulation of simulation models developed in a wide variety of tools. However, the ability to export industrially relevant models in a standardized way is merely the first step in simulating the targeted coupled sub-systems. Selecting a platform for efficient simulation of the system under investigation is the next step. Here, a strategy for adapting coupled Modelica models of aircraft vehicle systems to TLM-based simulation is presented. An industry-grade application example is developed, implementing this strategy, to be used for preliminary investigation and evaluation of a cosimulation framework supporting the Transmission Line element Method (TLM). This application example comprises a prototype of a small-scale aircraft vehicle systems simulator. Examples of aircraft vehicle systems are environmental control systems, fuel systems, and hydraulic systems. The tightly coupled models included in the application example are developed in Dymola, OpenModelica, and Matlab/Simulink. The application example is implemented in the commercial modelling tool Dymola to provide a reference for a TLM-based master simulation tool, supporting both FMI and TLM. The TLM-based master simulation tool TLMSimulator is investigated in terms of model import according to the FMI standard with respect to a specified set of industrial needs and requirements.

  • 15.
    Hällqvist, Robert
    et al.
    Systems Simulation and Concept Design, Saab Aeronautics, Linköping, Sweden.
    Schminder, Jörg
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten.
    Eek, Magnus
    Systems Simulation and Concept Design, Saab Aeronautics, Linköping, Sweden.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Gårdhagen, Roland
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    NOVEL FMI AND TLM-BASED DESKTOP SIMULATOR FORDETAILED STUDIES OF THERMAL PILOT COMFORT2018Inngår i: ICAS congress proceeding, International Council of the Aeronautical Sciences , 2018, artikkel-id ICAS2018_0203Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Modelling and Simulation is key in aircraft systemdevelopment. This paper presents a novel,multi-purpose, desktop simulator that can beused for detailed studies of the overall performanceof coupled sub-systems, preliminary controldesign, and multidisciplinary optimization.Here, interoperability between industrially relevanttools for model development and simulationis established via the Functional MockupInterface (FMI) and System Structure andParametrization (SSP) standards. Robust anddistributed simulation is enabled via the TransmissionLine element Method (TLM). The advantagesof the presented simulator are demonstratedvia an industrially relevant use-case wheresimulations of pilot thermal comfort are coupledto Environmental Control System (ECS) steadystateand transient performance.

  • 16.
    Krus, Petter
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Eriksson, Björn
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska högskolan.
    Aircraft System Simulation for Preliminary Design2012Inngår i: ICAS 2012 CD-ROM PROCEEDINGS / [ed] Professor I Grant, Optimage Ltd , 2012, s. Art.nr. ICAS2012-1.9.3-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Developments in computational hardware and simulation software have come to a point where it is possible to use whole mission simulation in a framework for conceptual/preliminary design. This paper is about the implementation of full system simulation software for conceptual/preliminary aircraft design. It is based on the new Hopsan NG simulation package, developed at the Linköping University. The Hopsan NG software is implemented in C++. Hopsan NG is the first simulation software that has support for multi-core simulation for high speed simulation of multi domain systems.

    In this paper this is demonstrated on a flight simulation model with subsystems, such as control surface actuators.

  • 17.
    Nordin, Peter
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Job-Scheduling of Distributed Simulation-Based Optimization with Support for Multi-Level Parallelism2015Inngår i: Proceedings of the 56th Conference on Simulation and Modelling (SIMS 56): October, 7-9, 2015, Linköping University, Sweden, Linköping: Linköping University Electronic Press, 2015, s. 187-197Konferansepaper (Fagfellevurdert)
    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.

  • 18.
    Sjölund, Martin
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Braun, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluid och mekanisk systemteknik.
    Towards Efficient Distributed Simulation in Modelica using Transmission Line Modeling2010Inngår i: 3rd International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The current development towards multiple processor cores in personal computers is making distribution and parallelization of simulation software increasingly important. The possible speedups from parallelism are however often limited with the current centralized solver algorithms, which are commonly used in today’s simulation environments. An alternative method investigated in this work utilizes distributed solver algorithms using the transmission line modeling (TLM) method. Creation of models using TLM elements to separate model components makes them very suitable for computation in parallel because larger models can be partitioned into smaller independent submodels. The computation time can also be decreased by using small numerical solver step sizes only on those few submodels that need this for numerical stability. This is especially relevant for large and demanding models. In this paper we present work in how to combine TLM and solver inlining techniques in the Modelica equation-based language, giving the potential for efficient distributed simulation of model components over several processors.

1 - 18 of 18
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