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Encapsulation in Object-Oriented Modelling for Mechanical Systems Simulation: Comparison of Modelica and BEAST
Linköping University, Department of Computer and Information Science. (PELAB)
Linköping University, Department of Computer and Information Science. (PELAB)ORCID iD: 0000-0002-3435-4996
Linköping University, Department of Computer and Information Science. (PELAB)
2009 (English)In: Proceedings of MATHMOD 2009 / [ed] I. Troch and F. Breitenecker, 2009Conference paper (Refereed)
Abstract [en]

In systems engineering and object-oriented design, encapsulation is a key concept to handle complexity. Interfaces are defined for the external interaction of a component, whereas internal details are hidden. Complex systems such as cars or airplanes consist of many components, which, in turn, consist of many components – hierarchically, through many levels. Therefore composition is built into modelling languages such as Modelica. External interfaces must be defined for external interaction, whereas internal components cannot be accessed if they are not available through these interfaces.

However, in 3D mechanical systems modelling and design, it is natural to be able to connect components whose surfaces are externally available. For example, the motor belonging to a car can be externally accessible in the 3D view, even though it can be regarded as an internal component of the car.

In this paper we compare two modelling approaches, one is Modelica used for systems engineering as well as modelling of multi-body systems and the other one is BEAST which is a specialised multi-body systems tool with good support for contact modelling. The current Modelica approach requires strict interfaces with encapsulation of internal components, whereas BEAST allows connections to internal components which are visible in a 3D view, which is often natural from the 3D mechanical systems point of view. For 3D mechanical systems, Modelica might be too strict, whereas BEAST might be too forgiving. Two different solutions are presented and discussed (in the form of possible Modelica extensions) to combine the advantages of both approaches.

Place, publisher, year, edition, pages
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-60302ISBN: 978-3-901608-35-3OAI: diva2:356113
MATHMOD 2012 - 7th Vienna International Conference on Mathematical Modelling, February 15 - 17, Vienna, Austria
Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2014-10-08
In thesis
1. Contributions to Modelling and Visualisation of Multibody Systems Simulations with Detailed Contact Analysis
Open this publication in new window or tab >>Contributions to Modelling and Visualisation of Multibody Systems Simulations with Detailed Contact Analysis
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The steadily increasing performance of modern computer systems is having a large influence on simulation technologies. It enables increasingly detailed simulations of larger and more comprehensive simulation models. Increasingly large amounts of numerical data are produced by these simulations.

This thesis presents several contributions in the field of mechanical system simulation and visualisation. The work described in the thesis is of practical relevance and results have been tested and implemented in tools that are used daily in the industry i.e., the BEAST (BEAring Simulation Tool) tool box. BEAST is a multibody system (MBS) simulation software with special focus on detailed contact calculations. Our work is primarily focusing on these types of systems.

focusing on these types of systems. Research in the field of simulation modelling typically focuses on one or several specific topics around the modelling and simulation work process. The work presented here is novel in the sense that it provides a complete analysis and tool chain for the whole work process for simulation modelling and analysis of multibody systems with detailed contact models. The focus is on detecting and dealing with possible problems and bottlenecks in the work process, with respect to multibody systems with detailed contact models.

The following primary research questions have been formulated:

  • How to utilise object-oriented techniques for modelling of multibody systems with special reference tocontact modelling?
  • How to integrate visualisation with the modelling and simulation process of multibody systems withdetailed contacts.
  • How to reuse and combine existing simulation models to simulate large mechanical systems consistingof several sub-systems by means of co-simulation modelling?

Unique in this work is the focus on detailed contact models. Most modelling approaches for multibody systems focus on modelling of bodies and boundary conditions of such bodies, e.g., springs, dampers, and possibly simple contacts. Here an object oriented modelling approach for multibody simulation and modelling is presented that, in comparison to common approaches, puts emphasis on integrated contact modelling and visualisation. The visualisation techniques are commonly used to verify the system model visually and to analyse simulation results. Data visualisation covers a broad spectrum within research and development. The focus is often on detailed solutions covering a fraction of the whole visualisation process. The novel visualisation aspect of the work presented here is that it presents techniques covering the entire visualisation process integrated with modeling and simulation. This includes a novel data structure for efficient storage and visualisation of multidimensional transient surface related data from detailed contact calculations.

Different mechanical system simulation models typically focus on different parts (sub-systems) of a system. To fully understand a complete mechanical system it is often necessary to investigate several or all parts simultaneously. One solution for a more complete system analysis is to couple different simulation models into one coherent simulation. Part of this work is concerned with such co-simulation modelling. Co-simulation modelling typically focuses on data handling, connection modelling, and numerical stability. This work puts all emphasis on ease of use, i.e., making mechanical system co-simulation modelling applicable for a larger group of people. A novel meta-model based approach for mechanical system co-simulation modelling is presented. The meta-modelling process has been defined and tools and techniques been created to fully support the complete process. A component integrator and modelling environment are presented that support automated interface detection, interface alignment with automated three-dimensional coordinate translations, and three dimensional visual co-simulation modelling. The integrated simulator is based on a general framework for mechanical system co-simulations that guarantees numerical stability.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 16 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1337
National Category
Engineering and Technology
urn:nbn:se:liu:diva-60303 (URN)978-91-7393-317-9 (ISBN)
Public defence
2010-10-29, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:14 (Swedish)
Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2014-10-08Bibliographically approved

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