| 1. |
- Bachmann, Bernhard, et al.
(author)
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Parallel Multiple-Shooting and Collocation Optimization with OpenModelica
- 2012
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In: Proceedings of the 9th International MODELICA Conference; September 3-5; 2012; Munich; Germany. - : Linköping University Electronic Press. - 9789175198262 ; , s. 659-668
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Conference paper (peer-reviewed)abstract
- Nonlinear model predictive control (NMPC) has become increasingly important for today’s control engineers during the last decade. In order to apply NMPC a nonlinear optimal control problem (NOCP) must be solved which needs a high computational effort.State-of-the-art solution algorithms are based on multiple shooting or collocation algorithms; which are required to solve the underlying dynamic model formulation. This paper describes a general discretization scheme applied to the dynamic model description which can be further concretized to reproduce the mul-tiple shooting or collocation approach. Furthermore; this approach can be refined to represent a total collocation method in order to solve the underlying NOCP much more efficiently. Further speedup of optimization has been achieved by parallelizing the calculation of model specific parts (e.g. constraints; Jacobians; etc.) and is presented in the coming sections.The corresponding discretized optimization problem has been solved by the interior optimizer Ipopt. The proposed parallelized algorithms have been tested on different applications. As industrial relevant application an optimal control of a Diesel-Electric power train has been investigated. The modeling and problem description has been done in Optimica and Modelica. The simulation has been performed using OpenModelica. Speedup curves for parallel execution are presented.
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| 2. |
- Brinkrolf, Christoph, et al.
(author)
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Modeling and Simulating the Aerobic Carbon Metabolism of a Green Microalga Using Petri Nets and New Concepts of VANESA
- 2018
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In: Journal of integrative bioinformatics. - : De Gruyter Open. - 1613-4516. ; 15:3
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Journal article (peer-reviewed)abstract
- In this work we present new concepts of VANESA, a tool for modeling and simulation in systems biology. We provide a convenient way to handle mathematical expressions and take physical units into account. Simulation and result management has been improved, and syntax and consistency checks, based on physical units, reduce modeling errors. As a proof of concept, essential components of the aerobic carbon metabolism of the green microalga Chlamydomonas reinhardtii are modeled and simulated. The modeling process is based on xHPN Petri net formalism and simulation is performed with OpenModelica, a powerful environment and compiler for Modelica. VANESA, as well as OpenModelica, is open source, free-of-charge for non-commercial use, and is available at: http://agbi.techfak.uni-bielefeld.de/vanesa.
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| 3. |
- Brinkrolf, Christoph, et al.
(author)
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VANESA : An open-source hybrid functional Petri net modeling and simulation environment in systems biology
- 2021
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In: Biosystems (Amsterdam. Print). - : Elsevier Ireland Ltd. - 0303-2647 .- 1872-8324. ; 210
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Journal article (peer-reviewed)abstract
- Petri nets are a common method for modeling and simulation of systems biology application cases. Usually different Petri net concepts (e.g. discrete, hybrid, functional) are demanded depending on the purpose of the application cases. Modeling complex application cases requires a unification of those concepts, e.g. hybrid functional Petri nets (HFPN) and extended hybrid Petri nets (xHPN). Existing tools have certain limitations which motivated the extension of VANESA, an existing open-source editor for biological networks. The extension can be used to model, simulate, and visualize Petri nets based on the xHPN formalism. Moreover, it comprises additional functionality to support and help the user. Complex (kinetic) functions are syntactically analyzed and mathematically rendered. Based on syntax and given physical unit information, modeling errors are revealed. The numerical simulation is seamlessly integrated and executed in the background by the open-source simulation environment OpenModelica utilizing the Modelica library PNlib. Visualization of simulation results for places, transitions, and arcs are useful to investigate and understand the model and its dynamic behavior. The impact of single parameters can be revealed by comparing multiple simulation results. Simulation results, charts, and entire specification of the Petri net model as Latex file can be exported. All these features are shown in the demonstration case. The utilized Petri net formalism xHPN is fully specified and implemented in PNlib. This assures transparency, reliability, and comprehensible simulation results. Thus, the combination of VANESA and OpenModelica shape a unique open-source Petri net environment focusing on systems biology application cases. VANESA is available at: http://agbi.techfak.uni-bielefeld.de/vanesa. © 2021 The Authors
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| 4. |
- Buffoni, Lena, et al.
(author)
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Open source languages and methods for cyber-physical system development : Overview and case studies
- 2021
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In: Electronics (Switzerland). - Basel : MDPI AG. - 2079-9292. ; 10:8
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Journal article (peer-reviewed)abstract
- Industrial cyber-physical system products interleave hardware, software, and communication components. System complexity is increasing simultaneously with increased demands on quality and shortened time-to-market. To effectively support the development of such systems, we present languages and tools for comprehensive integrated model-based development that cover major phases such as requirement analysis, design, implementation, and maintenance. The model-based approach raises the level of abstraction and allows to perform virtual prototyping by simulating and optimizing system models before building physical products. Moreover, open standards and open source implementations enable model portability, tool reuse and a broader deployment. In this paper we present a general overview of the available solutions with focus on Modelica/OpenModelica, Bloqqi, and Acumen. The paper presents contributions to these languages and environments, including symbolic-numeric modeling, requirement verification, code generation, model debugging, design optimization, graphical modeling, and variant handling with traceability, as well a general discussion and conclusions.
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| 5. |
- Fritzson, Peter, 1952-, et al.
(author)
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The OpenModelica Integrated Environment for Modeling, Simulation, and Model-Based Development
- 2020
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In: Modeling, Identification and Control. - Kristiansand, Norway : Norsk Forening for Automatisering. - 0332-7353 .- 1890-1328. ; 41:4, s. 241-295
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Journal article (peer-reviewed)abstract
- OpenModelica is a unique large-scale integrated open-source Modelica- and FMI-based modeling, simulation, optimization, model-based analysis and development environment. Moreover, the OpenModelica environment provides a number of facilities such as debugging; optimization; visualization and 3D animation; web-based model editing and simulation; scripting from Modelica, Python, Julia, and Matlab; efficient simulation and co-simulation of FMI-based models; compilation for embedded systems; Modelica-UML integration; requirement verification; and generation of parallel code for multi-core architectures. The environment is based on the equation-based object-oriented Modelica language and currently uses the MetaModelica extended version of Modelica for its model compiler implementation. This overview paper gives an up-to-date description of the capabilities of the system, short overviews of used open source symbolic and numeric algorithms with pointers to published literature, tool integration aspects, some lessons learned, and the main vision behind its development.
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| 6. |
- Kircher, Katja, 1973-, et al.
(author)
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Rural cycling in focus
- 2024
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Reports (other academic/artistic)abstract
- Even though cycling is slowly starting to get recognised as the sustainable mode of transport it is, this is mostly limited to short trips in urban areas. However, also in rural environments the bicycle has potential to replace the car for many trips. Best practice and research findings from urban areas cannot necessarily be directly applied to the rural environment, as preconditions can differ substantially. Speeds are higher, most interactions are longitudinal, the road is often shared, and the trip purposes and road users are likely to have different characteristics. This is also reflected in the differences in crash typology for rural and urban environments. This project aimed at further describing conflicts on rural roads between motorists and active travellers in a Swedish context by analysing crash statistics. The development of a logger that provides measurements of overtaking and oncoming passes in detail and can in the future then be used to quantify the context for situations that do not result in a (documented) collision. This way, collisions can be put into perspective for example in relation to the context (road type, speed limit, average annual daily traffic, etc.). Objective and reliable measurements of longitudinal interactions between motorists and active road users – namely overtaking and oncoming passes – are one important ingredient to assessing the current situation and the effectiveness of potential countermeasures. The measurement devices used in research so far are usually custom-built and the data reduction process is often not fully transparent. Within this project, we built an expandable device for logging the lateral distance to overtaking and oncoming vehicles and the approach speed of overtaking vehicles. The process to extract the passing occasions and the correct overtaking distance is made available as open source.
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| 7. |
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| 8. |
- Sjölund, Martin, 1984-, et al.
(author)
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Integrated Debugging of Equation-Based Models
- 2014
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In: Proceedings of the 10th International Modelica Conference. - : Linköping University Electronic Press. - 9789175193809 ; , s. 195-204
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Conference paper (peer-reviewed)abstract
- The high abstraction level of equation-based object-oriented languages (EOO) such as Modelica has the drawback that programming and modeling errors are often hard to find. In this paper we present the first integrated debugger for equation-based languages like Modelica; which can combine static and dynamic methods for run-time debugging of equation-based Modelica models during simulations. This builds on and extends previous results from a transformational static equation debugger and a dynamic debugger for the algorithmic subset of Modelica.
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