Linköping Studies in Science and Technology Dissertation No. 1337
Contributions to Modelling and Visualisation of Multibody
Systems Simulations with Detailed Contact Analysis
by
Alexander Siemers
Department of Computer and Information Science Linköpings universitet
SE-581 83 Linköping, Sweden
To my children
Erik, Joel, and Lisa
Abstract
The steadily increasing performance of modern computer systems is having a large influence on simulation technologies. It enables increas-ingly 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 Sim-ulation Tool) tool box. BEAST is a multibody system (MBS) simSim-ulation software with special focus on detailed contact calculations. Our work is primarily 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 pro-cess. The work presented here is novel in the sense that it provides a complete analysis and tool chain for the whole work process for simula-tion 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 to contact modelling?
• How to integrate visualisation with the modelling and simulation process of multibody systems with detailed contacts.
• How to reuse and combine existing simulation models to simulate large mechanical systems consisting of 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 bod-ies and boundary conditions of such bodbod-ies, 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 pre-sented here is that it presents techniques covering the entire visualisation process integrated with modelling 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 dif-ferent 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., mak-ing mechanical system co-simulation modellmak-ing applicable for a larger group of people. A novel meta-model based approach for mechanical system co-simulation modelling is presented. The meta-modelling pro-cess 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 trans-lations, and three dimensional visual co-simulation modelling. The inte-grated simulator is based on a general framework for mechanical system co-simulations that guarantees numerical stability.
Acknowledgements
The work presented in this thesis is a joint effort between the Programming Environment Laboratory (PELAB) at Link¨oping University and SKF Group Technology Development.
First would I like to thank my advisor Dag Fritzson and co-advisor Peter Fritzson for initiating this work and making this thesis possible at all. Special thanks to Dag Fritzson for co-authoring most of the papers in this thesis.
Thanks to all the people at PELAB for creating a nice working environ-ment at the university. Special thanks go to Iakov Nakhimovski for all BEAST cooperation, team-work in lectures and courses, and interesting discussions. I also would like to thank Vadim Engelson for all support and fruitful discussions around different topics of this thesis.
Many thanks to current and former BEAST team members at SKF: Lars-Erik Stacke, Mikael Holgerson, H˚akan B˚astedt, Alexei Jolkin, Jonas St˚ahl, Klas Modin, Pietro Tesini, Stefan Nielsson, and Eric Svensson for all support and helpful discussions and for making the office such a pleasant working place.
I am also grateful to all the administrative staff at IDA, especially Lillemor Wallgren and Bodil Mattson-Kihlstr¨om.
Finally, I would like to thank my wife Ulrika for all support and patience, my parents in Germany, and my friends in different countries around the world for all moral support and belief in my ability to finalize this work and write this thesis.
Alexander Siemers G¨oteborg October 2009
This work has been supported by SKF, the Swedish Foundation for Strategic Research (SSF/ProViking), the Excellence Center in Computer Science and Systems Engineering in Link¨oping (ECSEL), and the Knowledge Foundation (KK-stiftelsen/the Industry Graduate School).
Contents
1 Overview 1
1.1 BEAST - Tool Box . . . 1
1.2 Objectives . . . 3
1.3 Main Contributions . . . 5
1.4 Visualisation of Dynamic Multibody Simulation Data . . . 6
1.5 Meta-Modelling for Mechanical System Co-Simulation . . . 9
1.6 Object-Oriented Modelling of Mechanical Systems . . . 12
2 Overview of the Papers 13
Paper 1
17
3 Introduction 19 3.1 Multibody Simulation . . . 203.2 Overview of the Visualisation Process . . . 20
3.3 Requirements on the Visualisation System . . . 22
4 Related Work 23 4.1 General Visualisation Systems . . . 23
4.2 Visualisation of Large Data Sets . . . 23
4.3 Visualisation of CFD and FEA Data . . . 24
4.4 MSC.ADAMS - Multibody Simulation tool . . . 24
5 Object Oriented Modelling of Multibody Systems 25 6 Surface Representations for Multibody Systems 26 6.1 Continuous Surface Representations . . . 26
6.2 Discrete Surface Representations . . . 27
6.3 Surface Representations Used in this Work . . . 27
7 Classification of Simulation Data 28 8 Data Storage and Access 29 8.1 Compression of Time-Varying Scalar and Vector Data . . . 29
8.2 Storage of Scalar and Vector Data for Fast and Selective Access 30 9 Visualisation techniques for different types of data 31 10 The Visualisation System 32 10.1 Body and Surface Rendering . . . 32
10.2 Visualising Multibody Dynamics . . . 33
10.3 Vector Data (Forces and Motions) . . . 33 v
10.4 Presenting Visualisation Results . . . 34
10.5 Hardware Requirements for the Visualisation System . . . 35
11 Conclusion 35
Paper 2
39
12 Introduction 41 12.1 System Design . . . 4312.2 Data Classification . . . 43
12.3 Organisation of this Paper . . . 45
13 The Visualisation Process 45 13.1 File Storage for Efficient Data Access . . . 46
13.2 Data Compression . . . 47
13.2.1 Common Compression Techniques . . . 47
13.2.2 Transient Data Compression in BEAST . . . 47
13.3 Efficient Memory Management . . . 48
13.3.1 Performance Evaluation . . . 51
13.3.2 Memory and File Size Evaluation . . . 51
13.4 Surface Representations . . . 52
13.4.1 Discrete Surface Representations . . . 52
13.4.2 BEAST Surface Representations . . . 53
13.5 Surface Data Mapping . . . 55
13.5.1 Common Methods . . . 56
13.5.2 Surface Data Visualisation . . . 56
13.6 Rendering Stage . . . 57
14 Scalability of the Visualisation System 58 15 User Interaction 59 16 Conclusion 60
Paper 3
65
17 Introduction 67 17.1 Sub-Surface Data . . . 68 17.2 Parallel Simulation . . . 68 17.3 Requirements . . . 69 vi18 Related Work 69
18.1 Visualisation of Large Data Sets . . . 69
18.2 Volume Visualisation . . . 70
19 A Data Structure for Sub-Surface Data 70 20 Visualisation of Sub-Surfaces 71 21 Surface Data Packaging for Parallel Simulation 72 21.1 Packing Technique . . . 72
22 Conclusion 73
Paper 4
77
23 Motivation 79 24 Transmission Line Modelling 80 25 Simulation Framework 81 26 Modelica as Meta-Model Language 82 26.1 Meta-Model Class Library . . . 8226.2 Component Modelling . . . 84 26.3 Meta Modelling . . . 85 26.4 Meta-Model Translation . . . 86 26.5 Meta-Model Example . . . 86 27 Conclusion 90
Paper 5
93
28 Motivation 95 29 Meta-Modelling 96 29.1 Meta Model Representations . . . 9729.2 Meta Modelling Language . . . 99
30 Meta-Modelling Environment 101 30.1 External Models . . . 102
30.2 Interface Alignment . . . 103
31 Verification 103
32 Conclusion 104
Paper 6
107
33 Introduction 109 34 Meta-Models 111 34.1 Meta-Model Language . . . 113 34.2 Meta-Model Editor . . . 116 35 Co-Simulation Framework 11635.1 Requirements on External Model Simulators . . . 117
36 Transmission Line Based Co-simulations 118
36.1 TLM Background Theory . . . 119 36.2 Benefits of TLM Element . . . 121 37 Meta-Model Simulation 122 38 System Verification 124 39 Performance Evaluation 126 40 Conclusion 128
Paper 7
131
41 Introduction 13342 Grinding Spindle Application 134
43 Meta-Model based Co-Simulation 135
43.1 Meta-Models . . . 135
44 Co-Simulation Framework 136
44.1 Transmission Line Modelling . . . 137
45 Grinding Spindle Model 139
45.1 External Models . . . 140 45.2 Time and Loading Conditions . . . 141
46 Results 144
46.1 Conclusion . . . 144 viii
Paper 8
149
47 Introduction 151
47.1 Modelling and simulation environments . . . 152 47.2 Structuring of this paper . . . 152 48 Object-Oriented concepts applied to multibody-systems 154 48.1 Associations in object-oriented models . . . 155 49 Tools for modelling mechanical system simulations 155 49.1 Modelica and BEAST/BML . . . 156 50 Contact modelling and encapsulation for 3D mechanics 157
51 Model libraries and model composition 164
51.1 Model composition . . . 165
52 Conclusion 166
Glossary
172
1
Overview
Simulations of system models offer a cost effective and safe way for the investi-gation of mechanical systems. Accordingly, this approach has gained increasing attention in the industry. Instead of using an expensive and complex test-rig, a simulation program (a virtual test-rig) is used, which often saves time and money. Simulation models are generally more flexible than hardware proto-types, i.e., they are easy to adjust to new system properties, and output can be gathered on demand. Some of the advantages of simulations are:
• Design modifications are simple. Several designs can be tested without high manufacturing costs.
• Development time can be reduced significantly.
• Some parts within mechanical systems are difficult or impossible to mea-sure. Simulations on the other hand allow investigation of any part of the system that can be physically modelled.
• Low risk.
The steadily increasing performance of modern computer systems has a sig-nificant influence on simulation technologies. Increased computer performance enables more detailed simulations. A growing amount of numerical data is produced by these simulations. This is especially true for transient (dynamic) simulations, for instance, dynamic multibody simulations.
All parts of the work described in this thesis have practical relevance and have been tested and implemented in tools that are used daily in the industry, i.e., the BEAST “BEAring Simulation Tool” tool box.
1.1
BEAST - Tool Box
The BEAST project was initiated by SKF with the intention of creating a three dimensional dynamic rolling bearing simulation tool for simulation of bearings under predefined loading conditions. A decade later BEAST is a fully functional dynamic simulation program for different types of multibody systems. BEAST is a “Tool-Box” that consists of several tools for conducting simulations and analysing simulation results, see Figure 1. The tools are:
Beast is the tool that conducts the numerical simulation. Beast takes a param-eter file as input that describes the model geometry, boundary conditions, and other simulation and model specific parameters. The outcome of the numerical simulation is large sets (up to several gigabyte) of dynamic data.
Input Output RunBeast ViewBeast Beauty Beast Out2In
Figure 1: The BEAST Tool Box.
Beauty is an advanced 3D visualisation and animation tool. It is used for pre-and post-processing of BEAST simulations. All input parameters pre-and all model geometry is defined and verified during pre-processing. Beauty supports different methods for post-processing of simulation data, some of which are: animation of time dependent data, motion magnification, and visualisation of contact related data such as contact forces and pressure distributions. Much of the work presented here has been accomplished within the scope of this tool.
Out2In is used to convert simulation output files to input files. This is useful for restarting simulation from a certain time step, typically to test different input parameters within a certain time frame of the simulation.
RunBeast is used to start and monitor simulations on remote machines. Beast supports parallel simulation, i.e., simulations are typically submitted to a computer cluster where a single simulation utilises several CPU (Cen-tral Processing Unit) cores simultaneously to shorten simulation time. RunBeast provides the interface to the computer cluster from the users machine, where users typically run the BEAST software on a workstation or laptop.
ViewBeast is an advanced tool for two dimensional plotting of simulation data. Scalars and vectors can be investigated. ViewBeast supports time-frame selection, labelling, storage of plot descriptions, and much more. A calculator is provided to create user defined mathematical expressions based on Beast output variables.
1.2
Objectives
Research in the field of simulation modelling is typically focusing 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 method chosen to achieve this is to analyse the complete work-process for modelling and simulation of
multibody systems with detailed contact models and focus on possible problems and bottlenecks. A typical work process for modelling and simulation can be
divided into three steps:
1. Pre-processing (modelling). For mechanical systems with detailed contacts this preferably involves a graphical user interface with three di-mensional detailed surface modelling and visualisation capabilities. This is because calculation of detailed surface contacts requires detailed surface models.
2. Simulation. The actual calculation of detailed contact models often requires long simulation time and might produce a lot of simulation data that needs to be analysed.
3. Post-processing (data analysis). Data selection and visualisation techniques are typically used when analysing large amounts of data pro-duced by a simulation program. For mechanical system simulation a graphical user interface with three dimensional visualisation capabilities is desirable.
Unique in this work is the focus on detailed contact models. It influences the work process in all its phases and puts special requirements on the multibody system model, data handling, and the graphical user interface, including visual-isation techniques. Furthermore, the work presented here addresses mechanical system co-simulation modelling. The fundamental questions addressed in this work are:
• How to integrate visualisation with the modelling and simulation process
of multibody systems with detailed contacts?
Dynamic, or transient, simulations often produce large amounts of data. This is especially true for computation intensive simulations where a sin-gle simulation execution can take up to several days. Re-running such simulations is time consuming and thus costly. In such situations it is ad-vantageous to store all information that might be of interest (and that can be produced) right from the beginning, i.e., to avoid additional simulation executions. Visualisation and data-selection techniques are then needed to analyse the large amount of data. Large data sets put special require-ments on a visualisation system. Moreover, detailed contact analysis is
used to investigate surface related phenomena such as, contact pressure distribution, rolling contact fatigue, and wear. This puts high demands on the contact geometry, i.e., detailed surface and contact descriptions are needed. Part of this thesis is concerned with visualisation of large transient data sets and detailed contact phenomena.
• How to reuse and combine existing simulation models to simulate large
me-chanical systems consisting of several sub-systems by means of co-simulation modelling?
Different simulation models typically focus on different parts (sub-systems) of a mechanical system, e.g., the gear-box of a car, the drive-line, or even a single bearing inside the gear-box. To fully understand the complete mechanical system it is necessary to investigate several or all parts simul-taneously. This is especially true for transient (dynamic) simulations with several interconnected parts. One solution for a more complete system analysis is to couple different simulation models to form one coherent sim-ulation. This is sometimes called a coupled simulation or co-simsim-ulation. Co-simulations often interconnect two specific simulators where a unique interface between these tools is defined. However, a more general solution is needed to make co-simulation and co-simulation modelling easy to apply to a larger range of tools. Part of this thesis describes a general approach for modelling and management of mechanical system co-simulations. Fur-thermore focus co-simulation modelling approaches typically on data han-dling, connection modelling, and numerical stability. Here all emphasis is put on ease of use, i.e., making mechanical system co-simulation modelling applicable for a larger group of people.
• How to utilise object-oriented techniques for modelling of multibody
sys-tems with special reference to contact modelling?
At the lowest and most fundamental level of mechanical system mod-elling there are mathematical formulations. More specifically this means that the different physical properties of a mechanical system are described with mathematics, i.e., equations, mathematical functions, formulae, etc. However, when dealing with modelling of complete systems a pure math-ematical description of the system might be hard to formulate. Higher abstraction is therefore needed for large systems especially with respect to reusability, maintainability, and adjustability, i.e., testing different mathe-matical models, algorithms, and mechanical parts within the same system. Part of this thesis deals with this class of problems through techniques for object-oriented modelling of mechanical systems. Special focus is put on encapsulation in conjunction with contact modelling.
1.3
Main Contributions
The main contributions of this work can be summarised as follows:
• Integration of the complete visualisation process for multibody simulation
data including techniques and tools for: surface and data visualisation,
data storage, image rendering, and user interfaces. Visualisation research typically focuses on one detailed visualisation issue, e.g., a new compres-sion algorithm for 3D meshes. The novel visualisation aspect of the work presented here is that it presents techniques covering the entire visualisa-tion process integrated with modelling and simulavisualisa-tion.
• A novel sparse data structure that supports efficient lossless compressed storage, access, and network transport of multi dimensional transient data sets that are produced by detailed surface-to-surface contact calculations. One important aspect in visualisation of contact related data is to pro-cess two dimensional data that often has sparse topology. Existing data structures for sparse 2D data sets, e.g., sparse matrices, are typically opti-mised for efficient data storage but often lack features that are needed for time continuous simulation and visualisation, e.g., fast random data ac-cess and fast memory reallocation. This is addressed by the data structure presented here.
• A generic and uniform approach to connect various simulation tools by
means of a meta-model. Distributed co-simulation implementations
of-ten lack flexibility, i.e., they suffer from specialised interfaces between the simulation tools and system dependency, i.e., network parameters, tool dependent parameters, and machine names are stored in the model. The meta-models presented here provide a generic way to connect vari-ous simulation tools. Well defined interfaces are used that allow a uni-form connection of the tools. All operating system, network, or other co-simulation-platform dependent parameters are strictly separated from the meta-model. Furthermore, the meta-model is based on a language representation with strict notation and grammar. Graphical language el-ements are possible for visual representations of the meta-model. • A novel meta-model based approach for mechanical system co-simulation
modelling is presented. A meta-modelling process for co-simulation
mod-elling has been defined. The different phases of a meta-modmod-elling process have been identified. This work puts all emphasis on ease of use, i.e., identifies obstacles in the different phases that might hinder the usage of co-simulation and co-simulation modelling and presents solutions. Tech-niques and tools for co-simulation meta-modelling have been designed to make meta-modelling for mechanical system co-simulation applicable,
cluding tools for simulation model encapsulation, model verification, and visual (3D) meta-modelling.
• Comparison of different object-oriented modelling approaches applied to
multibody system simulations with detailed contact descriptions. Different
tools with support for multibody simulation exist, some of which use object oriented models for the multibody system. Two such approaches to modelling have been compared in this work with special focus on surface contact modelling and its relation to the object oriented model.
• Implementation of the presented techniques in an industrial multibody simulation system called BEAST.
1.4
Visualisation of Dynamic Multibody Simulation Data
Visualisation of simulation results is present everywhere in areas of modelling and simulation. There are general simulation tools, such as multi physics sim-ulation tools, i.e., Simulink [9], Ptolemy-II [2], and Modelica [4] based envi-ronments [8] and Dymola [3] that provide block diagrams for the modelling phase and sometimes simple 3D visualisation and animation for the analysis of mechanical system simulations. Concerning multibody system modelling these tools suffer from a lack of 3D pre-processing and detailed visual post-processing. Multibody system simulation tools, such as, MSC-ADAMS [10], typically sup-port 3D visualisation both, for pre- and post-processing. These tools have lim-ited capabilities for very detailed analysis of contact related phenomena, e.g., slip velocity, pressure distribution, fatigue, structural deformations (local and global), and material removal. It requires very detailed surface models and visu-alisation. More general visualisation tools, such as, ParaView [7], TechPlot [15], or OpenDX [5], provide many features for multi domain data exploration but cannot handle large transient data sets that contain thousands of variables. Typically, they require to extract and transform certain data sets and time se-ries to be able to analyse the data partially. A more integrated and complete approach is desirable from a usability point of view.
In the work presented here visualisation is fully integrated with modelling and simulation:
• Models are created using a tool which provides three dimensional repre-sentations of the entire model with detailed contact surface modelling. • Visualisation is entirely based on the simulation model. Any change in
the model structure directly affects the visual representation of the model. • Large amounts of dynamic data can be analysed by means of three di-mensional animation, including: selection of data set and time interval, visualisation of system dynamics with geometry changes, etc.
Part of this thesis deals with the visualisation of data produced by BEAST. Specialised visualisation techniques and tools are advantageous when analysing BEAST data. The core application utilised for the research presented here is Beauty, the 3D visualisation tool of BEAST, see Figure 2. Visualisation of mechanical systems and related data is not a new problem. Furthermore, the work presented here does not focus on one specific aspect of that field. Instead this work is concerned with how several aspects are integrated in one specific application area, i.e., multibody system dynamics with detailed contact analy-sis. More specifically concerning visualisation of data produced by simulations of bearings and bearing related applications. As stated in [6] there is little previous work concerned with the understanding of the integrated visualisation process itself. In the work presented here the entire visualisation process for these specific data sets has been analysed and transformed into a complete and working integrated visualisation system, see Paper 1 and Paper 2 for details. Paper 1 puts more emphasis on the visualisation process with background in-formation while Paper 2 presents the techniques designed and implemented in Beauty in more detail.
Figure 2: Beauty, the 3D visualisation tool of the BEAST tool-box. It offers
a model tree view and a full 3D view on the system. Part of a universal-joint model with some contact related data is shown.
Table 1: Performance and programming effort on different application and API
levels.
Low programming effort Other simulation MSC.ADAMS, ABAQUS,
Less performance tools ...
General visualisation Amira, OpenDX,
tools ...
Visualisation 3D Master Suite, VTK,
libraries ...
High level 3D Open Inventor, Open libraries Scene Graph, ... High programming effort low level 3D OpenGL, PEX,
High performance libraries Direct3D, ...
Generally, the choice of the visualisation system or architecture is a balance between programming effort and performance, see Table 1. On the high end there are existing simulation tools that solve certain problems and bring their own visualisation tools. At the low end there are low level 3D libraries that offer the best performance but require some programming effort. Different solutions have been tested for the data used here. Other simulation tools do not satisfactorily solve the problems addressed by BEAST, at least not regarding integration and desired detail. We found that general visualisation tools and higher level visualisation libraries have performance issues with the amount of data and number of variables used here. OpenGL [17] has been chosen as the graphics API for Beauty because it offers good performance, the highest level of flexibility, and portability.
So, what is a multibody system and what are the specific characteristics of the data created by BEAST? Multibody systems are used to model and in-vestigate mechanical systems in which several bodies interact with each other. Examples of multibody systems are: rolling bearings, gearboxes, and cars. Sim-ulations are conducted to increase the understanding of the dynamic behaviour and interaction between the bodies. Detailed contact analysis is used to inves-tigate surface related phenomena such as, contact pressure distribution, rolling contact fatigue, and wear. This puts high demands on the contact geometry, i.e., detailed surface and contact descriptions are needed. For instance, con-tacts between two bodies often result in local surface deformation, e.g., wear, material removal and structural deformation of the body, such as, flexibility or elasticity. To achieve this, new adaptive visualisation techniques for surfaces are presented in this work, including: dynamic surface meshes with level of detail methods, see Sections 13.4.2 and Section 15, and user adjustable magnification
mechanisms, see Section 15. Furthermore, contact calculations are computa-tion intensive and when applied to transient problems result in large amounts of multidimensional data, both in the time domain, i.e., many thousands of time steps, and in the data domain, e.g., pressure distribution over the surface or higher order tensors for material stresses. Techniques for handling this type of data include: lossless data compression, see Section 13.2, and a new adaptive data structure for two dimensional surface related data sets, see Section 13.3 and Section 13.5.2. Contact stresses between two surfaces affect the material underneath the surface. These stresses need to be stored during simulation and visualised during animation. This work classifies these stresses as sub-surfaces, thus a thin layer volume underneath the surface of the body. Techniques, in-cluding a new data structure, for storage and visualisation of sub-surface data are described in Paper 3.
It should be noted that BEAST and Beauty are mainly used for bearing applications with focus on detailed contact modelling. However the techniques presented in this thesis can also be applied to other application areas where contact plays an important role, e.g., gearwheel contacts, ball screws, roller screws, and ring grinding applications.
1.5
Meta-Modelling for Mechanical System Co-Simulation
Part of this work is concerned with co-simulation modelling based on a general framework for meta-model based co-simulations, see Paper 4, Paper 5, and [11] for details about the framework. Existing co-simulation environments typi-cally define communication interfaces by means of network addresses and data types and thus introduce system dependent co-simulation models that often require manual startup of all the simulation tools involved. Furthermore, in the best case, these environments support two dimensional block diagrams for co-simulation modelling to represent the interconnections between the different co-simulation components. The work presented here introduces meta-modelling for mechanical system co-simulation where the meta-model defines the physi-cal interconnections of various external models. An external model is a model defined in some specific modelling language supported by modelling and simu-lation tools that can perform a simusimu-lation of it. Each external model has one or more, but can have several external interfaces for connection to other exter-nal models. By interconnecting several exterexter-nal models, the (extended) overall structure of the system model is created.
Co-simulation implementations often lack portability and flexibility, i.e., they suffer from specialised interfaces between the simulation tools and gen-erate system dependent models. The meta-modelling approach presented here provides a generic way of connecting various simulation tools. Well defined interfaces are used that allow a uniform connection of the tools. Common co-simulation environments such as, for instance, Cosimate [16], often exchange
data using a shared memory model, i.e., two connected simulation tools write data into a certain memory address that is provided and managed by the co-simulation environment. These connections are defined in terms of memory ad-dresses and data types and do not guarantee numerically stable co-simulation. The external interfaces defined in the work presented here introduce a higher level of abstraction by defining unified interfaces in terms of mechanical ve-locity and reaction forces, and provide a numerically stable method by means of TLM, see also Section 36. One issue of distributed co-simulations is porta-bility, i.e., co-simulation models often contain system dependent parameters such as, for instance, network ports and machine names that are needed to run the different simulation tools and models involved in a co-simulation. In the meta-model approach presented in this work all operating system, network, or other co-simulation-platform dependent parameters are strictly separated from the meta-model. Instead, the system requires one initial set-up to be able to run meta-model based co-simulations, see also Section 37. This implies that the meta-model based co-simulation could theoretically run on other architec-tures than the presented co-simulation environment as well, e.g., the High-Level Architecture [1] (HLA). Furthermore, the meta-model language representation, with strict notation and grammar, allows sharing of meta-model information between different tools and people, see also Section 29.2. Different tools can be adapted to read and process the complete meta-model. Graphical language ele-ments allow for three-dimensional visual representations of the external models. The early work presented in Paper 4 utilises the Modelica [4] language to describe the meta-model in an easy to understand, object oriented way. A ModelicaXML [12] based translator is used to convert Modelica code to an XML document which is accepted as input by the co-simulation engine. Later this work has been further extended to improve meta-model simulation pre-and post-processing, i.e., fully three dimensional model editor pre-and meta-model animations, see Paper 4 for details about the modelling environment and the defined meta-modelling process. Furthermore, the XML based language has later been redesigned to remove XML-tags for improved readability, adding hierarchical constructs to allow for hierarchical meta-models, and integrating geometrical elements for improved meta-model visualisation.
Model abstraction, where each external model is represented uniformly and independently form a simulation-tool, is an important feature of the meta-model. Every external-model can be seen as a black-box, with unified interfaces, representing a particular simulation tool. Meta-models can thus be designed, shared, and discussed without the need to understand the simulation tools that are involved in the co-simulation.
Meta-models also simplify centralised co-simulation control, where a single simulation manager can execute and control the co-simulation based on the meta-model. Correct simulation tool start-up and communication between the tools can be managed and monitored in a better way. This allows a controlled
reaction on execution and communication problems and to log all communicated data. Paper 6 discusses the meta-model based co-simulation environment in detail.
All the work described here is of practical relevance and has been realised within the scope of the BEAST tool box. An example of a meta-model based co-simulation is presented in Paper 7. A rotor-dynamics application, a grinding spindle arrangement, is presented that contains several non-linear components, e.g., two ball bearings supporting the spindle shaft and a control system deter-mining the rotation of the shaft. A total of four simulation models have been connected by means of a meta-model that contains an MSC.ADAMS [10] spin-dle model, two BEAST [14] ball bearings fixing the shaft in the housing, and a Simulink [9] driver that controls the rotation of the shaft.
To advance the applicability of co-simulation meta-modelling the different phases of the meta-modelling process have been identified. Unique in this work is the focus on the user perspective on the meta-model process for mechanical system co-simulations, i.e., ease of use. Here a classification and partitioning of the process into three stages has been defined: external model design, model integration, and meta-model design, see Section 29 and Section 34 for details. To fully support the complete process in all its stages an external model inte-grator and meta-model editor have been created that support, for instance, au-tomated external interface detection, interface alignment with auau-tomated three dimensional coordinate translations, and three dimensional visual co-simulation modelling, see Section 30.
In conclusion, the following methods and tools are utilised to support ease of use in co-simulation modelling:
• Based on a framework that supports numerically stable co-simulation, interface plugin that can be adjusted to many simulation tools, automatic unit adjustment, and more, see Paper 4, Paper 5, and [11] for details. • Meta-model based co-simulation that provides:
System independent models, Meta-model designer does not need to know about computer system and network details.
Model abstraction, where each external model is represented uni-formly and independently of a simulation tool.
A generic and uniform way to connect various simulation tools. All tools implement a single unified external interface.
• Meta-model editor with three dimensional visual representations of the external models, all interfaces, connections, and model hierarchy. Exter-nal models are visualised using standard virtual reality markup language (VRML) files.
• An external model integrator for easy simulation model encapsulation and integration. Model files, VRML files, and start method need to be entered. All files are automatically copied into the meta-model archive.
• Automated external interface detection. External interfaces are defined in the specific simulation tools of the external model, e.g., BEAST, MSC-ADAMS, or Modelica. For mechanical system co-simulations correct po-sition and orientation of the interface is required. Also names of interfaces are needed for correct connection modelling. Often the meta-model de-signer does not have knowledge of all the simulation tools involved and might not have appropriate information about all the interfaces. There-fore the external model integrator can request this information directly from the simulation model through the co-simulation framework. • External Interface alignment. A correct meta-model requires that any two
connected TLM interface points have the same start position and orienta-tion relative to the meta-models global inertial coordinate system. In some cases the different modelling tools use different local inertial coordinate systems. To avoid redesign of the external model in its specific modelling environment the meta-model editor allows for the alignment of any two selected interface points automatically. The calculated transformations are stored in the meta-model.
• Execution in separate directories. All external models are automatically executed in separate directories during the co-simulation. This to avoid naming conflicts, i.e., the same external model can be used more than once in a meta-model.
1.6
Object-Oriented Modelling of Mechanical Systems
A mechanical system simulation can be based on several mathematical models each of which represents a physical phenomenon. Expressing the behaviour of a large mechanical system with basic mathematical formulations, i.e., just sys-tems of equations without additional structuring information, is typically hard to achieve. A higher level of abstraction is therefore needed for modelling and simulation of large mechanical systems. Especially with respect to reusability, maintainability, and adjustability, i.e., testing different mathematical models, algorithms, or system set-ups. One approach to model abstraction is to di-vide the model into several interacting components that can be handled one by one. A common method for representing mechanical systems as interdepen-dent components is called multibody system modelling. Another, more general, method is called object-oriented modelling [13]. One key concept to handle complexity in object-oriented design is encapsulation. Interfaces are defined for the external interaction of a component, whereas internal details are hidden.
Complex systems such as, for instance, cars or airplanes consist of many com-ponents, 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.
Paper 8 introduces basic object-oriented concepts, with applications to multi-body systems with detailed contact models. Modelica-based tools and the BEAST tool and their application to multi-body system modelling are dis-cussed. Section 50 discusses and compares different concepts of encapsulation and mechanical contacts in the context of multi-body system modelling, with special reference to the Modelica and BEAST approaches. It is argued that interface propagations as used in Modelica provides clean interface definitions with data encapsulation and information hiding. This approach works well for modelling of many systems but is not sufficient for convenient modelling of multibody contacts where globally accessible interfaces are needed in the context of accessible mechanical surfaces and components. It is briefly demon-strated that simple modifications to the Modelica language would allow for more convenient connection modelling through multiple hierarchical levels.
2
Overview of the Papers
This thesis consists of several papers, three that present multibody data visual-isation, four addressing meta-modelling for mechanical co-simulation, and one that is concerned with object oriented modelling of mechanical systems. Here follows a short overview of the papers:
1. Visualisation of Dynamic Multibody Simulation Data.
This paper describes what is needed to create a complete multibody visu-alisation system. The complete visuvisu-alisation process, from data storage to image rendering is discussed. Special attention is placed on visualisation of multibody dynamics and contact related vector data, e.g., forces and moments.
2. Visualisation and Data Representation for Large-Scale Multi-body Simulations with detailed contact analysis.
Beauty, an integrated visualisation and simulation tool for multibody-systems with detailed contact analysis applied to transient dynamics is presented in this paper. The simulation program produces a large amount of data and many time steps which requires data compression. A lossless compression algorithm specially designed for time-varying data is used. Selective data access is required for visualisation of transient data sets.
A block based streaming technique with fast selective data access is pre-sented that allows for realistic animations of mechanical system dynamics. Furthermore, different representations of surfaces and surface related data are presented that are used throughout the visualisation process. 3. Sub-Surface Visualisation and Parallel Simulation.
This paper focuses on the visualisation of contact stresses. Contact stresses between two surfaces penetrate the material underneath the surface. These stresses need to be stored during simulation and visualised during anima-tion. They are classified as sub-surfaces, thus a thin layer volume under-neath the surface. A sub-surface data structure is presented that inherits properties of the earlier defined surface data structure and adds addi-tional capabilities for visualisation of volumes. Another topic is parallel simulation that puts special demands on the surface data and sub-surface data structures. Data has to be packed and distributed to the different simulation nodes efficiently, in order to achieve good speed-up. Special attributes of the data are used to minimise the data to be packed. To achieve fast data transmission, all data is packed into one buffer. 4. Meta-modelling of Mechanical Systems with Transmission Line
Joints in Modelica.
A framework for meta-modelling with Transmission Line (TLM) joints is presented. The framework is intended to support transient simulations of mechanical systems using co-simulation of different tools. The expressive power of the Modelica language is used to describe the meta-model in an easy to understand, object oriented way. The main focus is on modelling of co-simulation Meta-Models taking advantage of Modelicas graphical and object-oriented modelling capabilities.
5. A Meta-Modelling Environment for Mechanical System Co-Simulations. This paper presents a general approach for modelling of mechanical system
co-simulations. The concept of meta-modelling is applied to mechanical co-simulations. Several tool-specific simulation models can be integrated and connected by means of a meta-model, which defines the physical in-terconnections of these models. A fully functional modelling environ-ment is described that features a graphical user interface for co-simulation modelling with support for three dimensional visual representation of the co-simulation meta-model including all its components. The modelling environment supports easy encapsulation and integration of simulation tool-specific models.
6. General Meta-Model Based Co-Simulations Applied to Mechan-ical Systems.
The meta-model co-simulation environment that supports integration of 14
many different simulation tool specific models into a co-simulation is de-scribed in this paper. The presented approach for mechanical system co-simulations is based upon a general framework for co-simulation and meta-modelling. Several tool specific simulation models can be inte-grated and connected by means of a meta-model. A platform indepen-dent, centralised, meta-model simulator is presented that executes and monitors the co-simulation. All simulation tools that participate in the co-simulation implement a single, well defined, external interface that is based on a numerically stable method for force/moment interaction. 7. Non-Linear Rotor-Dynamics Modelling using Co-Simulation.
This paper describes a rotor-dynamics application, a grinding spindle ar-rangement, that has successfully been modelled and simulated using the general framework for co-simulation and meta-modelling. Four simulation models have been connected by means of a meta-model, that contains an MSC.ADAMS spindle model, two BEAST ball bearings fixing the shaft in the housing, and a Simulink driver that controls the rotation of the shaft. Rotor-dynamics effects, such as, grinding-wheel vibrations and stiffness are presented to verify the results of the simulation.
8. Object-Oriented Modelling for Mechanical-System Simulations — Comparison of Modelica and BEAST models.
The application of object oriented techniques to mechanical system mod-elling is discussed in this paper. The focus is on modmod-elling of multibody systems. BEAST and Modelica — a language for multi-physics simula-tions, are used as reference, both of which have object oriented modelling support, are used as reference. The main differences between these ap-proaches are pointed out and discussed.
References
[1] IEEE Standard 1516-2000. High level architecture (hla) - framework and rules. IEEE Standard for Modeling and Simulation, May 2000.
[2] J. Eker, J. W. Janneck, E. A. Lee, J. Liu, X. Liu, J. Ludvig, S. Neuendorf-fer, S. Sachs, and Xiong Y. Taming heterogeneity—the ptolemy approach. In Proceedings of the IEEE, volume 91. IEEE, January 2003.
[3] H. Elmqvist. Dymola user’s manual - version 5.0a, 2002. http://www.dynasim.com.
[4] P. Fritzson. Object-Oriented Modeling an Simulation with Modelica 2.1. Wiley-Interscience, 2004.
[5] Opendx - software package for the visualization of scientific, engineering and analytical data, 2010. http://www.opendx.org.
[6] T.J Jankun-Kelly, Ma Kwan-Liu, and M. Gertz. A model for the visual-ization exploration process. Visualvisual-ization, 2002. VIS 2002. IEEE, pages 323–330, Nov. 2002.
[7] Paraview - an open-source, multi-platform data analysis and visualization application, 2010. http://www.paraview.org.
[8] Mathmodelica - model based design of multi-engineering systems, 2010. http://www.mathcore.com/products/mathmodelica.
[9] Simulink - simulation and model-based design, 2010. http://www.mathworks.com/products/simulink/.
[10] Msc software corporation website, 2008. http://www.mscsoftware.com. [11] I. Nakhimovski. Contributions to the Modeling and Simulation of
Me-chanical Systems with Detailed Contact Analysis. PhD thesis, Link¨opings
universitet, Sweden, 2006. Dissertation No. 1009.
[12] A. Pop and P. Fritzson. Modelicaxml:a modelica xml representation with applications. In Modelica 2003 Conference, 2003.
[13] J. Rumbaugh, M. Blaha, W. Premerlani, F. Eddy, and W. Lorensen.
Object-Oriented Modeling and Design. Prentice-Hall, Inc., 1991.
[14] L-E. Stacke, D. Fritzson, and P. Nordling. BEAST—a rolling bearing simulation tool. Proc. Instn Mech. Engrs, part K, Journal of Multi-body
Dynamics, 213:63–71, 1999.
[15] Techplot - powerful analysis and visualization software, 2010. http://www.techplot.com.
[16] TNI-Software. Cosimate co-simulation software. Homepage, 2008. [17] M. Woo, J. Neider, and T. Davis. OpenGL Programming Guide.
Addison-Wesley Publishing Company, Inc., 2nd edition, 1998.
Department of Computer and Information Science Linköpings universitet
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