The object-oriented modeling language Dymola allows the physical modeling of large interconnected systems based on model components from different engineering domains. It generates symbolic code for different target simulators. In this paper, a Dymola class library for the efficient generation of the equations of motion for multibody systems is presented. The library is based on an O(n) algorithm which is reformulated in an object-oriented way. This feature can also be interpreted as a bond graph oriented modeling of multibody systems. Furthermore a new algorithm for a certain class of variable structure multibody systems, such as systems with Coulomb friction, is presented, which allows the generation of efficient symbolic code.

This report describes MM, a computer program that can model a variety of mechanical and fluid systems. It addresses several issues: What is the appropriate input to the modeling process? How should the search for models be organized? What evidence can be brought to bear to constrain the task? MM takes as input both a description of the structure of the system to be modeled and a trace of the system's behavior. The structure can be represented by 2D line drawings augmented with some additional information, or by component types and their interconnections, or both. The behavior trace provides the program with qualitative information about the behavior that the user wishes to capture with a model. MM organizes its search for models using a generalized, energy-based modeling framework and represents its models using bond graphs, a notation optimized for that framework. The program searches the system structure for plausible locations of primitive elements, connects the elements together ...

This article introduces the concept of combining both form (CAD models) and behavior (simulation models) of mechatronic system components into component objects. By connecting these component objects to each other through their ports, designers can create both a systemlevel design description and a virtual prototype of the system. This virtual prototype, in turn, can provide immediate feedback about design decisions by evaluating whether the functional requirements are met in simulation. To achieve the composition of behavioral models, we introduce a port-based modeling paradigm. The port-based models are reconfigurable, so that the same physical component can be simulated at multiple levels of detail without having to modify the system-level model description. This allows the virtual prototype to evolve during the design process and to achieve the accuracy required for the simulation experiments at each design stage. To maintain the consistency between the form and behavior of compone...

The field of design science attempts to place engineering design on a more formal, rigorous footing. This paper introduces recent work by the author in this area. Artifact-Centered Modeling (ACM) is a general framework intended to partition the design endeavor in manageable sections. A fundamental part of ACM is the representation of information about products being designed. The Axiomatic Information Model for Design (AIM-D) is a formal theory about product information based on axiomatic set theory. AIM-D provides formal bases for quantities, features, parts and assemblies, systems, and subassemblies; these are all notions essential to design. It is not a product modeling system per se, but rather a logic of product structure whose axioms define criteria for determining the logical validity of product models. A previous version of the theory has been found to contain logical inconsistencies; the version presented herein addresses those problems. A complete axiomatization of the new th...

We illustrate the importance of a well-defined ontology for representing and integrating different types of engineering design knowledge with examples taken from bridge design. In particular, we focus on two types of knowledge: synthesis knowledge about the generation of design products, and design standards against which the generated products have to be evaluated. It is shown how both types can be represented using YMIR, an ontology for engineering design. By using the same ontological basis for the synthesis knowledge and the design standards, both types of knowledge can be used in an integrated way by the design process. in: Artificial Intelligence in Design'94, J.S. Gero and F. Sudweeks (eds.), Kluwer Academic Publishers, 1994, pp 517-534. 1.

An important recent idea to facilitate knowledge sharing is to provide libraries of reusable components (models, ontologies) to end users. However, when libraries become large, finding the right library components is a knowledge demanding task in itself. Our suggestion therefore is that methods will be needed that help the user to gradually construct such knowledge.

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The complete control system design effort involves many stages during which partial design tasks are completed. Each of these tasks requires different modeling paradigms and different tools. Furthermore, the designed embedded control system entails a wide variety of implementation technologies that all require different specification formalisms. To handle such a multitude of modeling paradigms and different support tools: (i) a unifying generic standard language can be applied, and (ii) the required modeling paradigms can be modeled by a meta model using a shared meta language. An overview of the required parts and structure of a modeling environment and of the two approaches is given. The advantages with respect to multi-paradigm modeling are discussed.

hybrid systems, physical system modeling, bond graphs, hybrid bond graphs, hydraulic actuators Bond graphs are a powerful formalism to model continuous dynamics of physical systems. Hybrid bond graphs introduce an ideal switching element, the controlled junction, to approximate continuous behavior that is too complex for numerical analysis (e.g., because of nonlinearities or steep gradients). HyBrSim is a tool for hybrid bond graph modeling and simulation implemented in Java and documented in this paper. It performs event detection and location based on a bisectional search, handles run-time causality changes, including derivative causality, performs physically consistent (re-)initialization, and supports two types of event iteration because of dynamic coupling. It exports hybrid bond graph models in Java and C/C++ code that includes discontinuities as switched equations (i.e., pre-enumeration is not required). 1

Abstract: We present a novel approach for model-based FDI of abrupt faults in process components of continuous dynamic systems. Abrupt faults refer to parameter value changes that occur much faster than the nominal process dynamics, and component faults refer to faults that correspond to physical parameters in the bond graph model of a system. These faults cause transients in system behavior. We analyze this transient response by combining statistical detection and estimation with a model-based qualitative fault isolation engine. Detection uses the discrete wavelet transform in combination with a statistical decision function. Fault isolation is based on analysis of fault signatures in a qualitative framework. We demonstrate robust detection for small faults, and robust fault isolation that becomes more precise for larger faults. Copyright c 2003 IFAC