DESIGN AND DEVELOPMENT USING MODELICA
Adrian PopOlof Johansson2
1
Peter Fritzson3
Programming Environments Laboratory
Department of Computer and Information Science
Linköping University
58131 Linköping
Sweden
Abstract
This paper presents recent work in the area of model-driven product development processes. The focus is on the integration of product design tools with modeling and simulation tools. The goal is to provide automatic generation of models from product specifications using a highly integrated set of tools. Also, we provide the designer with the possibility of selecting the best design choice, verified through (automatic) simulation of different implementation alternatives of the same product model. To have a flexible interaction among various tools of the framework an XML representation of the Modelica modeling language called ModelicaXML is used. For efficient search in a large base of simulation models the Modelica Database was designed.
modeling and simulation tools in a framework for product design. In our proposed framework, the 1 Introduction and Related Work
product concept design phase of the product
Designing products is a complex process. Highly development process is based on Function-Means integrated tools are essential to help a designer to tree decomposition [7, 13]. This phase is work efficiently. Designing a product includes implemented in a first version of a prototype tool early design phase product concept modeling and called FMDesign, developed in cooperation with evaluation, physical modeling and simulation and the Machine Design Group led by Petter Krus, finally the physical product realization. For IKP, Linköping University. conceptual modeling and physical modeling and As an example of Function-Means tree simulation available tools provide advanced decomposition we give a landing function in an functionality. However, the integration of such airplane. This function can be represented by two tools is a resource consuming process that today different means: hydraulic landing gear or electric requires large amounts of manual, and error prone landing gear. Each of the two alternatives can be work. Also, the number of physical models selected and configured to simulate its properties. available to the designer in the product concept Starting from FMDesign tool, our integration design phase is typically quite large. This has an work extends the framework in two ways: impact on the selection of the best set of • Providing a Selection and Configuration Tool component choices for detailed product concept that helps the designer to choose a specific simulation. implementation for the means in the function- To address these issues we have integrated new means tree from a Modelica model/ product concept design tools with physical 1
Phone: +46 13 285781, Fax: +46 13 284499, Email: adrpo@ida.liu.se2
Fax: +46 13 284499, Email: olojo@ida.liu.se3
Phone: +46 13 281484, Fax: +46 13 284499, Email: petfr@ida.liu.secomponent database. This tool also provides component configuration and has links to a Modelica standard based simulation environment for component editing.
• Providing an Automatic Model Generation
Tool that helps the designer to choose the best implementation from different design choices by evaluation through simulation of
Requirementsautomatically Databasegenerated models of candidate product Reference Linksconcepts. If the designer is not pleased Product Concept Design Databasewith the results, F1he/she can either implement new M1aM1bM1cmodels for the components that did F1a.1 F1a.2F1a.3not perform in the desired way or Selection and Configuration reiterate in the design
Tool process and choose other alternatives for implementing
Modelica Model different functions in
Database the product, or change
the configuration parameters for models at deeper levels of detail.
The paper is structured as follows: The next section presents an overview of our proposed framework. Section 3 enters in the details of the framework components and their interaction. Section 4 presents our conclusion and future work.
The presented system has similarities with the Schemebuilder tool [8]. However our work is more oriented towards the design of advanced complex products that require systems engineering, and targeted to the simulation modeling language Modelica, which to our knowledge has more expressive power in the areas of our research, than many tools for systems engineering that are currently widely used. For details on Systems Engineering, see [2].
2 Architecture overview
The architecture of our extended framework is presented in Figure 1. The entire product concept design process is iterative.
F = FunctionM = Means Product ConceptDesign Tool(FMDESIGN)MeansEvaluations SimulationEvaluationOptimisationOperationCases EngineeringDesignSystem XAutomaticModelGeneratorToolModelicaXML Generated Models ModelicaSimulationSource code Figure 1: Design framework for product development Starting from requirements for a product the designer will use the FMDesign prototype for modeling alternative product concepts. The knowledge base for designing a product is organized into function-means trees. A function in the product can be realized by alternative means. A product concept is a set of means that document selected solution alternatives for implementing the functions in a product concept. Example of a function is \"Actuator Power Supply\", with means \"Hydraulic Power Supply\" or \"Electrical Power Supply\". Means must be implemented by (physical) components arranged in a bill-of-material like tree of implementation objects. One can roughly say that a means and its implementation are the same, but at different levels of detail. Implementation objects (not shown in the figure) may represent existing classTest \"comment\"component products on the market or Real x;modelicaxmlReal xdot;manufactured components. Implementation equationobjects carry data that is important for the Modelicaxdot= der(x);definition product concept design, and references to more endTest;codedetailed design information like CAD-drawings, equation componentreadsimulation models etc. Some (physical components) may implement several means, like Modelica Parsercomponent an aircraft wing that creates lift and stores fuel.
When the product concept design phase of the product is sufficiently complete, the designer can Figure 2: Modelica and the corresponding ModelicaXML generate code for simulation from the representation implementation tree using the Automatic Model
ModelicaXML represents an XML serialization of Generator Tool. The generator will output models
the Abstract Syntax Tree of the Modelica (different versions for different product concepts)
language obtained after the parsing. In our in ModelicaXML. From Modelica-XML the
framework, ModelicaXML is used as an models are translated to Modelica to be simulated.
interchange format between the different design The designer can review the simulation results in
tools. tools like MathModelica [3], Dymola [1] or
The advantages of having an alternative OpenModelica [10] and then selects (in
representation for Modelica in XML are: FMDesign) the desired model alternative for the
• Flexible interaction and translation between implementation. If the designer sees that some
different types of physical modeling means do not perform in the desired way, a
languages and modeling tools. Also, easy customized simulation model can be built, or a
generation of model documentation. search conducted for more alternatives for that
• Basic search and query functionalities over specific means.
models. • Easy transformation and composition of 3 Detailed framework description models [12]. In this section we present the tools from our For more information on ModelicaXML the proposed framework. Also, we briefly explain in reader is referred to [11] and [9]. each section how they interact. 3.2 Modelica Database (ModelicaDB) 3.1 ModelicaXML The features of the Modelica language and Modelica [4, 9] is an object-oriented language used for modeling of large and heterogeneous physical systems. For modeling with Modelica, commercial software products such as MathModelica [3] or Dymola [1] have been developed. However, there are also open-source projects like the OpenModelica Project [10]. Modelica is translated to ModelicaXML using a Modelica parser (Figure 2). Modelica tools has made easy for designers to create models. Also, the Modelica community has a growing code-base. In order to cope with interoperability between Modelica and other modeling languages we first developed ModelicaXML. However, scalability and efficient search features for XML require extensive skills in vendor specific products. To quickly get such features without taking on that huge learning effort, we have designed the Modelica Database (ModelicaDB). The Modelica Database is populated with Modelica models and libraries by importing their ModelicaXML representation. The UML model of this database is presented in the Appendix. For paper space reasons we use a somewhat customized compressed graphical representation of UML class diagrams, where inheritance is represented with a box between the class name and attributes box, where inherited super classes are preceded with a \"->\". For details on UML see [6]. Here we briefly explain the most important structures. They are tightly coupled with the Modelica structure [9, 11]:
• Modelica Repository: contains several
Modelica Models.
• Class: A class represents the fundamental
model element from the Modelica language. It can include several Component clauses, Equation and Algorithm statements. The component sections can be declared as public or private in order to provide only the desired interface to the outer world. Specifying that the equation or algorithm sections are only active at the initialization phase they can be declared as initial.
• Component: used to define parameters,
variables, constants, etc to be used inside a class.
• Equations and Algorithms are used to specify
the desired behavior for a class.
In the product design framework the role of ModelicaDB is to provide searching and organization features of a large base of simulation models. This base grows with every product model developed or with the import of additional simulation models from other sources (i.e. the Modelica community). For example, if we want to obtain all the models that have certain parameter names we have to search in the database for all classes that have a component with the attribute variabilityPrefix set to “parameter” and has the specified name. These searches will be integrated in FMDesign using dialogs and completely transparent for the user. 3.3 FMDesign
The FMDesign (Figure 3) prototype tool helps the designer in creating product specifications using function-means trees.
Figure 3: FMDesign
The created product model is stored in a product design library for later reuse. Throughout the product concept design process the designer can use the existing concepts stored in the product design library in order to model the desired product. A somewhat simplified meta-model of the information structure edited in FMDesign is presented as an UML class diagram in the appendix section. In the framework, FMDesign is the central front-end to specific components. FMDesign delegates searches in the ModelicaDB using the Selection and Configuration Tool and it uses the Automatic Model Generation Tool to generate the models for simulation. As we can see in Figure 3, the work area is divided into several parts:
• Products: Here products are created, deleted
and selected. When a product is selected, the trees owned by it and described below, are displayed.
• Requirements Tree: in this view the
requirements for a product can be specified. • Function-Means Tree: in this view the
designer can define the operation states, functions, their alternative means etc, of the selected product.
• Product Concepts: Allows creating, deleting
and selecting product concepts.
• Product Concept Tree: displays the currently
selected Product Concept Tree, and allows the user to select which means that will implement different functions in the product, using drag-drop. Selected means can be customized for the current product concept by overriding the default values for its design variables owned by a selected means.
• Implementation Tree: displays and provides
functionality for editing one of many configurable Implementation Trees for the currently selected product concept. These implementation trees organize the implementation objects that represent and refer to more detailed models of physical objects, functional models, simulation models, geometrical layout models etc, and organize them into trees that are useful for interfacing with tools later in the product development process.
We only use the Implementation Tree of type simulation to generate the Modelica simulation model for a product. The Implementation Tree of type geometrical can be used in the visualization of the product. 3.4
The Selection and Configuration Tool The Selection and Configuration Tool extends the framework by adding integrated search capabilities in FMDesign. The tool is coupled with the Implementation Tree for a Product Concept. The designer uses the selection tool to search (query) the Modelica Database for desirable simulation components to implement a certain means. An implementation object in the simulation implementation tree represents the selected simulation component. Simulation component to means mapping reflects the various design choices made by the designer. In this way, the designer can experiment with different simulation component implementations at various level of detail for a specific means. When choosing alternatives for a specific means the designer has two possibilities: to browse the repository of simulation models classified according to physical concepts or to use the search dialog. The search dialog provides the following functionality:
• Textual/pattern search of components, search
for a component in a specific physical domain, search for a component with specific parameters.
• Adding/deleting a product concept specific
means to simulation component mapping where the simulation component is referred from an implementation object.
After building the means-component mappings the designer can choose to edit or configure components by using the configuration dialog that provides the following functionality:
• Set implementation component parameters or
parameters ranges.
• Edit the simulation component in the desired
Modelica environment and use the edited component, which is also automatically added to the Modelica Database.
3.5 The Automatic Model Generator Tool
The Automatic Model Generator Tool provides the second extension of the framework. The model generator tool has as input the Implementation Tree (Figure 3, lower right) of a product and as output the complete simulation model with the alternative design choices.
The automatic model generator traverses the Implementation Tree of a Product Concept and outputs ModelicaXML models by choosing the combination of selected components for means. The generated models are then translated to Modelica for means evaluation through simulation. To simulate the models, commercial tools like Dymola and MathModelica or the open-source OpenModelica [10] compiler can be used. After the simulation of the generated models, the results are used as feedback for the designer. Using this feedback the designer can then choose the best-suited model, based on the simulation results.
4 Conclusions and Future Work
As future work we want to explore the use of ontologies for product concept design and for the classification of the available component libraries. The languages developed by the Semantic Web [5] community will be used. Research efforts based on this standard are integrating experience of many promising research areas, for instance declarative rules, which still lack a vendor neutral exchange formats for industrial applications. The semantic web standard lacks important functionality for quality assurance and other necessary functionality, which today is implemented in commercial products, but will open up for sharing of important research results with industry in collaborative environments. Also we would like to improve the Automatic Model Generator Tool by using parts of the composition and transformation framework described in [12]. In the future we want to provide automatic evaluation through simulation of the generated models based on the constraints collected from the Product's Requirement Tree.
5 Acknowledgements
The ProViking research program, created by the Swedish Foundation for Strategic Research supported this research through the project System Engineering and Computational Design (SECD). The National Computer Graduate School in Computer Science (CUGS) and Vinnova through the Semantic web for products (SWEBPROD) project.
6 References
1. Dynasim. Dymola, http://www.dynasim.se/.
2. INCOSE. International Council on System Engineering,
http://www.incose.org.
3. MathCore. MathModelica,http://www.mathcore.se/. 4. Modelica: A Unified Object-Oriented Language for
Physical Systems Modeling, Language Specification version 2.1, Modelica Association, 2003, 5. Semantic Web Community Portal,
http://www.semanticweb.org/. 6. OMG. Unified Modeling Language,
http://www.omg.org/uml.
7. Mogens Myrup Andreasen. Machine Design Methods
Based on a Systematic Approach (Syntesemetoder på systemgrundlag), Lund Technical University, Lund, Sweden, 1980.
8. R.H. Bracewell, D.A.Bradley. Schemebuilder, A Design
Aid for Conceptual Stages of Product Design, in International Conference on Engineering Design, IECD'93 1993, The Hague.
9. Peter Fritzson. Principles of Object-Oriented Modeling
and Simulation with Modelica 2.1, Wiley-IEEE Press, 2003, http://www.mathcore.com/drmodelica.
10. Peter Fritzson, Peter Aronsson, Peter Bunus, Vadim
Engelson, Levon Saldamli, Henrik Johansson and
Andreas Karstöm. The Open Source Modelica Project, in Proceedings of The 2th International Modelica Conference,March 18-19, 2002, Munich, Germany. 11. Adrian Pop, Peter Fritzson. ModelicaXML: A Modelica
XML representation with Applications, in International Modelica Conference,3-4 November, 2003, Linköping, Sweden.
12. Adrian Pop, Ilie Savga, Uwe Assmann and Peter
Fritzson. Composition of XML dialects: A ModelicaXML case study, in Software Composition Workshop 2004, affiliated with ETAPS 2004,3 April, 2004, Barcelona. 13. Sören Wilhelms, Reuse of Principle Solution Elements In
Conceptual Design. Lic. thesis 1044, Linköping University, 2003
7 Appendix
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