基于Modelica的多领域建模与联合仿真

为实现多领域建模仿真环境与其他仿真环境的联合仿真,提出基于Modelica多领域建模的联合仿真方案.该方案基于Modelica多领域模型的连接机制,通过Modelica模型与Simulink模块的转换机理,实现在S-Function联合仿真框架下的联合仿真.基于Modelica的多领域物理系统建模仿真工具MWorks与...     

Ring: A unifying meta-model and infrastructure for Smalltalk source code analysis tools

Source code management systems record different versions of code. Tool support can then compute deltas between versions. To ease version history analysis we need adequate models to represent source code entities. Now naturally the questions of their definition, the abstractions they use, and the APIs of such models are raised, especially in the context of a reflective system which already offers a model of its own structure.We believe that this problem is due to the lack of a powerful code meta-model as well as an infrastructure. In Smalltalk, often several source code meta-models coexist: the Smalltalk reflective API coexists with the one of the Refactoring engine or distributed versioning system such as Monticello or Store. While having specific meta-models is an adequate engineered solution, it multiplies meta-models and it requires more maintenance efforts (e.g., duplication of tests, transformation between models), and more importantly hinders navigation tool reuse when meta-models do not offer polymorphic APIs.As a first step to provide an infrastructure to support history analysis, this article presents Ring, a unifying source code meta-model that can be used to support several activities and proposes a unified and layered approach to be the foundation for building an infrastructure for version and stream of change analyses. We re-implemented three tools based on Ring to show that it can be used as the underlying meta-model for remote and off-image browsing, scoping refactoring, and visualizing and analyzing changes. As a future work and based on Ring we will build a new generation of history analysis tools.     

Co-simulation for performance prediction of integrated building and HVAC systems – An analysis of solution characteristics using a two-body system

Integrated performance simulation of buildings and heating, ventilation and air-conditioning (HVAC) systems can help in reducing energy consumption and increasing occupant comfort. However, no single building performance simulation (BPS) tool offers sufficient capabilities and flexibilities to analyze integrated building systems and to enable rapid prototyping of innovative building and system technologies. One way to alleviate this problem is to use co-simulation to integrate different BPS tools. Co-simulation approach represents a particular case of simulation scenario where at least two simulators solve coupled differential-algebraic systems of equations and exchange data that couples these equations during the time integration.This article analyzes how co-simulation influences consistency, stability and accuracy of the numerical approximation to the solution. Consistency and zero-stability are studied for a general class of the problem, while a detailed consistency and absolute stability analysis is given for a simple two-body problem. Since the accuracy of the numerical approximation to the solution is reduced in co-simulation, the article concludes by discussing ways for how to improve accuracy.     

无线网络环境下控制系统的仿真研究

由于无线网络控制系统的复杂化,在分析和设计的过程中,联合仿真是研究无线网络控制系统必须解决的关键问题之一.着重介绍一种基于MATLAB/SIMULINK的联合仿真工具--TRUETIME工具箱.首先介绍工具箱的组成,然后利用该工具箱,以直流电机为对象,建立一个无线网络控制系统仿真模型,最后数值仿真说明该方法的有效性.     

Integrating MOF-Compliant Analysis Results

With the increasing maturity of model-driven tools and methods, new model-based analysis methods are developed to support specific stakeholder concerns during software lifecycle. This multiplication of models and their related analysis tools calls for solution addressing the integration of MOF-based analysis methods. Current research works on integration of analysis methods have already addressed the extraction of the needed input data as well as the control and the integration of the tools supporting the analysis execution. However, little attention has been paid to the integration of analysis results back into initial model. We propose an MOF-based framework enabling the integration of analysis results that a) defines a meta-model capturing the integration requirements, b) provides an MOF meta-model extension mechanism with support for upward compatibility; and c) automatically generates a model transformation for model integration. We illustrate the use of our framework by integrating a reliability analysis methods and a fault tolerant reconfiguration method on the ABC/ADL Software Architecture. We applied the resulting analysis composition onto the ECPerf JEE system.     

Seamless interaction in virtual reality

Jot is a novel research interface for virtual reality modeling. This system seamlessly integrates and applies a variety of virtual and physical tools, each customized for specific tasks. The Jot interface not only moves smoothly from one tool to another but also physically and cognitively matches individual tools to the tasks they perform. In particular, we exploit the notion that gestural interaction is more direct, in many cases, than traditional widget based interaction. We also respect the time tested observation that some operations-even conceptually three dimensional ones-are better performed with 1D or 2D input devices, whereas other operations are more naturally performed using stereoscopic views, higher DOF input devices, or both. Ultimately we strive for a 3D modeling system with an interface as transparent as the interaction afforded by a pencil and a sheet of paper. For example, the system should facilitate the tasks of drawing and erasing and provide an easy transition between the two. Jot emerged from our previous work on a mouse based system, called Sketch, for gesturally creating imprecise 3D models. Jot extends Sketch's functionality to a wider spectrum of modeling, from concept design to detailed feature based parametric parts. Jot also extends the interaction in Sketch to better support individual modeling tasks. We extended Sketch's gestural framework to integrate interface components ranging from traditional desktop interface widgets to context sensitive gestures to direct manipulation techniques originally designed for immersive VR     

Using Meta-Modelling and Graph Grammars to Create Modelling Environments

This paper presents the combined use of meta-modelling and graph grammars for the generation of visual modelling tools for simulation formalisms. In meta-modelling, formalisms are described at a meta-level. This information is used by a meta-model processor to generate modelling tools for the described formalisms. We combine meta-modelling with graph grammars to extend the model manipulation capabilities of the generated modelling tools, as we store (meta-)models as graphs, and thus, express model manipulations as graph grammars.We show the design and implementation of these concepts in AToM³ (A Tool for Multi-formalism, Meta-Modelling). As an example we will present a meta-model for Causal Block Diagrams and a graph grammar to generate OOCSMP code, a continuous simulation language which has a compiler able to generate Java applets from the simulations models.     

On the effect of multirate co-simulation techniques in the efficiency and accuracy of multibody system dynamics

Dynamic simulation of complex mechatronic systems can be carried out in an efficient and modular way making use of weakly coupled co-simulation setups. When using this approach, multirate methods are often needed to improve the efficiency, since the physical components of the system usually have different frequencies and time scales. However, most multirate methods have been designed for strongly coupled setups, and their application in weakly coupled co-simulation is not straightforward due to the limitations enforced by commercial simulation tools used in mechatronics design. This work describes a weakly coupled multirate method intended to be a generic multirate interface between block diagram software and multibody dynamics simulators, arranged in a co-simulation setup. Its main advantage is that it does not enforce equidistant or synchronized communication time-grids and, therefore, it can be easily applied to set up weakly-coupled co-simulations using off-the-shelf commercial block diagram simulators while giving the user a great flexibility for selecting the integration scheme for each subsystem.     

基于HLA/局域网的异构仿真系统实现

高层体系结构(HLA)通过一套标准接口将异构的仿真节点封装为具有同样接口形式的联邦成员,支持异构模型的协同仿真。目前还没有统一的方法将不具备足够开放性、不能封装为HLA联邦成员的仿真节点集成到整个基于HLA框架的仿真系统中。为解决该问题,设计HLA/局域网混合的异构仿真结构,并按设计构建初步的仿真系统。测试证明系统稳定可靠,可满足仿真要求。     

Activity-based simulation using DEVS: increasing performance by an activity model in parallel DEVS simulation

Improving simulation performance using activity tracking has attracted attention in the modeling field in recent years. The reference to activity has been successfully used to predict and promote the simulation performance. Tracking activity, how- ever, uses only the inherent performance information contained in the models. To extend activity prediction in modeling, we propose the activity enhanced modeling with an activity meta-model at the meta-level. The meta-model provides a set of interfaces to model activity in a specific domain. The activity model transformation in subsequence is devised to deal with the simulation difference due to the heterogeneous activity model. Finally, the resource-aware simulation framework is implemented to integrate the activity models in activity-based simulation. The case study shows the improvement brought on by activity-based simulation using discrete event system specification （DEVS）.     

Modeling functional requirements for configurable content- and context-aware dynamic service selection in business process models

In this article, we propose a meta-model for formal specification of functional requirements for configurable content- and context-aware dynamic service selection in business process models with the objective to enable greater flexibility of the modeled processes. The dynamic service selection can cope with highly dynamic business environments that today's business processes must handle. Modeling functional requirements for dynamic service selection in business process models is not well covered in literature. Some partial solutions exist but none of them allows modeling a complete set of functional requirements for the selection similar to the one we are addressing in this article. Our meta-model enables formal specification of service selection relevant data extracted from service request message, custom configuration data (e.g., thresholds), process and task definition/instance metadata, and service selection rules. The meta-model is configurable and content- and context-aware. Processes leveraging our meta-model can adapt to changing requirements without redesign of the process flow. Proposed meta-model allows users to additionally configure the models at run time (e.g., raising a threshold). Modeling can be divided into roles with different required competences. We implement our meta-model in BPMN 2.0 (Business Process Model and Notation) through specific extensions to the BPMN semantic and diagram elements. By measuring complexity of real-world sample process models we show that using our solution modelers can efficiently model business processes that need to address frequent changing demands. Compared to available alternatives, models using our solution have on average ～13% fewer activities, ～16% fewer control-flow elements and ～22% fewer control paths. By reading ～10% smaller models (by volume) model readers get more flexible process models that capture all functional requirements for the dynamic selection.     

A Z-map update method for linearly moving tools

In numerically controlled (NC) machining simulation, a Z-map has been frequently used for representing the workpiece. Since the Z-map is usually represented by a set of z-axis aligned vectors, the machining process can be simulated through calculating the intersection points between the vectors and the surface swept by a machining tool. In this paper, we present an efficient method to calculate those intersection points when automatically programmed tool-type tools move along a linear tool path. Each of the intersection points can be expressed as the solution of a system of non-linear equations. We transform this system of equations into a single-variable equation, and calculate the candidate interval in which the unique solution exists. We prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the non-linear equations within a given precision. The whole process of NC simulation is achieved by updating the Z-map properly. Our method can improve accuracy greatly while increasing processing time negligibly in comparison with previous Z-map update methods, making it possible to verify the tool path more accurately and reliably.     

基于元模型的知识管理建模工具设计与开发

知识管理建模是构建组织知识管理系统的基础．组织知识管理建模远比信息管理建模复杂，迫切需要建模工具的支持．从知识内容和管理两个层面分析提出知识管理的建摸需求，以此为依据建立知识管理元模型．组织知识管理元模型包括组织战略、组织结构、组织流程和组织知识地图四个子模型．为了方便建模工具的开发，用组织知识管理对象建模语言集成各子模型对应的建模语言．在此基础上实现了一个知识管理建模工具．     

A Meta-Model for Model-Driven Web Development

Several model-driven development (MDD) techniques for web applications exist; these techniques use meta-models for defining transformations and designing models. In this paper, we propose a meta-model for abstract web applications that can be mapped to multiple platforms. We extend a UML-based model to support specific features of the Web and Web 2.0 as well as to establish a bridge to functional and usability requirements through use cases and user interface (UI) prototypes. The meta-model also helps avoid a common MDD-related problem caused by name-based dependencies. Finally, mappings to a number of specific web platforms are presented in order to validate the appropriateness of the meta-model as an abstract web model.     

Model-driven engineering techniques for the development of multi-agent systems

Model-driven engineering (MDE), implicitly based upon meta-model principles, is gaining more and more attention in software systems due to its inherent benefits. Its use normally improves the quality of the developed systems in terms of productivity, portability, inter-operability and maintenance. Therefore, its exploitation for the development of multi-agent systems (MAS) emerges in a natural way. In this paper, agent-oriented software development (AOSD) and MDE paradigms are fully integrated for the development of MAS. Meta-modeling techniques are explicitly used to speed up several phases of the process. The Prometheus methodology is used for the purpose of validating the proposal. The meta-object facility (MOF) architecture is used as a guideline for developing a MAS editor according to the language provided by Prometheus methodology. Firstly, an Ecore meta-model for Prometheus language is developed. Ecore is a powerful tool for designing model-driven architectures (MDA). Next, facilities provided by the Graphical Modeling Framework (GMF) are used to generate the graphical editor. It offers support to develop agent models conform to the meta-model specified. Afterwards, it is also described how an agent code generator can be developed. In this way, code is automatically generated using as input the model specified with the graphical editor. A case of study validates the method put in practice for the development of a multi-agent surveillance system.     

A novel tool for transient stability analysis of large-scale power systems: Its application to the KEPCO system

Time-domain simulation is an important tool for power system dynamic analysis. We solve a set of differential and algebraic equations (DAE) in order to study the dynamic behavior of power systems. These power systems include thousands of generators, exciters, turbine-governors, loads, and other devices. The resultant large-scale DAEs are very difficult to handle and solve. Nevertheless, solution techniques are needed to not just guarantee accuracy but have computational efficiency.In this paper, we report on a novel tool that we developed to deal with time-domain simulation for dynamic analysis and operation of large-scale power systems. The tool has several major features related to transient stability analysis, contingency screening, and ranking. We mainly discuss the structure of this tool and the accuracy of the included dynamic models. Also, the paper proposes a new load model to overcome the low-voltage problem. The proposed technique provides a good performance and convergence when the terminal voltage is below some predefined value. Compared to the commercial tools, the developed tool is numerically well conditioned by introducing the ZIP model algorithm. This tool has been used to support and enhance power engineering education at both the undergraduate and graduate levels. In the case study, simulation results were validated through comparative simulations with the Power System Simulator for Engineering (PSS/E) and Transient Security Assessment Tool (TSAT).     

Recent development of fluid–structure interaction capabilities in the ADINA system

The ADINA system has been developed in recent years into a complete system for the analysis of solid, fluid and coupled problems. Fluid flows can be modeled as Navier–Stokes incompressible, slightly compressible and fully compressible flows. They can also be modeled as porous medium flows. Structures can be modeled as 2D/3D solids, beams or shells. The response of the structure can be linear or nonlinear, and can also include contact effects. The fluid and structure can be coupled through their interface (FSI), porous media (PFSI) or thermal materials (TFSI). Both iterative and direct solution procedures can be used for solving the fully coupled system. These capabilities, together with the extensive boundary conditions and material models, and the user-friendly graphical system for pre- and post-processing (AUI), make the ADINA system a powerful tool for engineers and researchers.