This paper describes the modeling language CHARON for modular design of interacting hybrid systems. The language allows specification of architectural as well as behavioral hierarchy and discrete as well as continuous activities. The modular structure of the language is not merely syntactic, but is exploited by analysis tools and is supported by a formal semantics with an accompanying compositional theory of refinement. We illustrate the benefits of CHARON in the design of embedded control software using examples from automated highways concerning vehicle coordination

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Description languages that are used to capture the essential properties of embedded computer systems must also allow a description of the system's environment, which consists of a number of physical objects. The reason is that the environment is the ultimate source of all requirements on the system. However, most such languages, including the object-oriented ones, are not well equipped to describe the continuous-time relationships that exist in the real world. This paper shows how the Unified Modeling Language can be extended to include such modeling, thereby improving the design of embedded systems described in the same language. Two realistic examples are elaborated to show the practical usefulness of the results. The technique is also relevant to the area of systems engineering, which often deals with multi-disciplinary system development. Keywords: Physical modeling, object-oriented models, UML, embedded systems, systems engineering 2/10 1.

This paper concerns the static analysis for debugging purposes of programs written in declarative equation based modeling languages.

DCharts, a formalism for modeling and simulation of complex reactive software systems, is proposed and studied. The DCharts formalism is based on UML statecharts and DEVS, but provides better modularity and expressiveness. DCharts semantics is rigorously defined in both an operational way and in a denotational way. Abstract, textual, and visual syntax for DCharts are presented. SVM, a DCharts simulator implemented in Python, is presented. It accepts textual model descriptions and simulates them. Multiple types of simulations, as well as real-time execution, are discussed in detail with examples. Model verification is supported by means of repeated simulations in SVM and rule-checking of the simulation traces with extended regular expressions. SCC is a tool to synthesize executable code from DCharts models. It statically optimizes the models to achieve high run-time performance. Multiple target languages are supported. Applications of the DCharts formalism are studied, by means of the the above-mentioned tools. They demonstrate how DCharts are ready for practical use.

The complexity of mechanical and multi-domain simulation models is rapidly increasing. Therefore new methods and standards are needed for model design. A new language, Modelica, has been proposed by an international design committee as a standard, object-oriented, equationbased language suitable for description of the dynamics of systems containing mechanical, electrical, chemical and other types of components. However, it is complicated to describe the system models in textual form whereas CAD systems are convenient tools for this purpose. We have designed an environment that supports the translation from CAD models to standard Modelica notation. This notation is then used for simulation and visualization. Assembly information is extracted from the CAD models, from which a Modelica model is generated. By solving equations expressed in Modelica, the system is simulated. A 3D visualization tool based on OpenGL visualizes expected and actual model behavior, as well as additional parameters. The environment has been applied for robot and flight simulation.

Modern object oriented modeling techniques, such as the Modelica modeling language, are increasing the capability to model and simulate systems of large size and complexity. Simulation of such large and complex systems is computationally very expensive. The use of parallel computers for simulation of Modelica models is one approach of handling simulation of such large and complex systems within reasonable time limits. This paper presents an automatic parallelization tool that translates the sequential simulation code generated from a Modelica compiler, Dymola, into a parallel version that can be executed on a parallel computer. The paper also presents several scheduling and clustering techniques used by the tool to partition the simulation code onto several processors. One of these techniques, called FTDT-Full Task Duplication Technique, gives a measured speedup of 2.5 on an 8 pro- cessor PC-cluster. However, future work includes de- veloping better scheduling and clustering algorithms to further improve the results.

Modeling and simulation have become central to all disciplines of engineering and science. In a comprehensive modeling and simulation environment, it is desirable to integrate models specified in different modeling formalisms and to extend modeling language constructs to support multi-domain and multi-formalism modeling integrated with powerful visualization capabilities. This paper is concerned with the design of a complete integrated environment that combines the powerful mechanical model design of various CAD packages with the structuring mechanisms of object oriented modeling languages including a mathematical and logical behavior representation. We present an integrated environment for simulation of multi-domain models which has been implemented using Modelica as a standard model representation. The user can work with mechanical models designed with AutoDesk's Mechanical Desktop, extend the corresponding Modelica model in various ways, and analyze the simulation results in a high performance interactive visualization environment.

Modelica is an a-causal, equation based, object oriented modeling language for modeling and efficient simulation of large and complex multi domain systems. The Modelica language, with its strong software component model, makes it possible to use visual component programming, where large complex physical systems can be modeled and composed in a graphical way. One tool with support for both graphical modeling, textual programming and simulation is MathModelica.

Mathematical models containing partial differential equations (PDEs) occur in many engineering applications. Modelica is a general, high-level language for object-oriented modeling with differential-algebraic equations (DAEs). There is a need for extending Modelica to also support modeling with PDEs. This paper presents some ideas on such extensions to the Modelica language, that would allow formulation of PDE problems defined on general domains using objects.