Showing papers on "Systems modeling published in 2003"

Dynamic security-constrained rescheduling of power systems using trajectory sensitivities

Abstract: In the deregulated environment of power systems, the transmission networks are often operated close to their maximum capacity to achieve transfer of power. Besides, the operators must operate the system to satisfy its dynamic stability constraints under credible contingencies. This paper provides a method using trajectory sensitivity to reschedule power generation to ensure system stability for a set of credible contingencies while satisfying its economic goal. System modeling issue is not a limiting concern in this method, and hence, the technique can be used as a preventive control scheme for system operators in real time.

Identification of nonlinear physiological systems

Abstract: Preface. 1. Introduction. 1.1 Signals. 1.2 Systems and Models. 1.3 System Modeling. 1.4 System Identification. 1.5 How Common are Nonlinear Systems? 2. Background. 2.1 Vectors and Matrices. 2.2 Gaussian Random Variables. 2.3 Correlation Functions. 2.4 Mean-Square Parameter Estimation. 2.5 Polynomials. 2.6 Notes and References. 2.7 Problems. 2.8 Computer Exercises. 3. Models of Linear Systems. 3.1 Linear Systems. 3.2 Nonparametric Models. 3.3 Parametric Models. 3.4 State-Space Models. 3.5 Notes and References. 3.6 Theoretical Problems. 3.7 Computer Exercises. 4. Models of Nonlinear Systems. 4.1 The Volterra Series. 4.2 The Wiener Series. 4.3 Simple Block Structures. 4.4 Parallel Cascades. 4.5 The Wiener-Bose Model. 4.6 Notes and References. 4.7 Theoretical Problems. 4.8 Computer Exercises. 5. Identification of Linear Systems. 5.1 Introduction. 5.2 Nonparametric Time-Domain Models. 5.3 Frequency Response Estimation. 5.4 Parametric Methods. 5.5 Notes and References. 5.6 Computer Exercises. 6. Correlation-Based Methods. 6.1 Methods for Functional Expansions. 6.2 Block Structured Models. 6.3 Problems. 6.4 Computer Exercises. 7. Explicit Least-Squares Methods. 7.1 Introduction. 7.2 The Orthogonal Algorithms. 7.3 Expansion Bases. 7.4 Principal Dynamic Modes. 7.5 Problems. 7.6 Computer Exercises. 8. Iterative Least-Squares Methods. 8.1 Optimization Methods. 8.2 Parallel Cascade Methods. 8.3 Application: Visual Processing in the Light Adapted Fly Retina. 8.4 Problems 8.5 Computer Exercises. References. Index. IEEE Press Series in Biomedical Engineering.

Applied Simulation Modeling

Abstract: 1. INTRODUCTION. Model Building and Decision Making: OR/MS Tools. Simulation as a Tool to Analyze Models. Overview of Simulation Models. 2. SIMULATION CONCEPTS AND SPREADSHEETS. Definition of "Static" Simulation. Several Examples. 3. FINANCIAL MODELS AND RISK ANALYSIS USING @RISK. An Insurance Model to Estimate Loss Ratio. A Model for Stock (or Bond) Valuation. Option Pricing. A Portfolio Model. 4. DYNAMIC SYSTEM MODELS. Definition of Dynamic Systems. Characteristics of Dynamic Simulations. Examples. 5. DISCRETE EVENT SIMULATION. Dynamic Structure: Events and Event Sequencing. Examples. Static Structure: Entities, Attributes, Lists. Examples. Model Verification. 6. SYSTEM MODELING PARADIGMS. What is a Simulation World View? Event View. Activity View. Process View. 7. ARENA AND VISUAL INTERACTIVE SIMULATION. Visual Interactive Simulation (VIS). Overview of Arena. A Simple Queuing System in Arena. The System Modeling Process with Arena. 8. PROBLEM SOLVING USING SIMULATION. Waiting Line Systems (Service Systems). Manufacturing Systems. 9. GRAPHICAL MODELING. Graphical Models. Advantages of Graphical Modeling. Graphical Modeling Techniques. Execution of Graphical Models. 10. SIMULATION SOFTWARE. Types of Simulation Software. Simulation Languages. Simulation Environments. Simulation Libraries. Simulation Software for Special Purposes. 11. CONSIDERATIONS IN LARGE-SCALE SIMULATION. The Nature of Real-World Models. The Simulation Process. The Team Approach and the Need for Expertise. Working with Clients. Data Collection and Measurement. Model Organization: Submodels. Model Development and Testing. Evolutionary Model Building. A Case Study.

Architecting systems with UML 2.0

Abstract: Signaling the end of the method wars, the Object Management Group (OMG) first standardized the Unified Modeling Language in 1997. The software industry rapidly accepted it as the standard modeling language for specifying software and system architectures. Although UML is primarily intended for general-purpose modeling, it's receiving extensive use in diverse specialized areas, such as business process modeling and real-time-systems modeling. Despite these successes, development tools have been slow to realize UMLs full potential. In this article, we look at some major improvements proposed for UML 2.0.

A framework for model-based design of agent-oriented software

Abstract: Agents are becoming one of the most important topics in distributed and autonomous decentralized systems, and there are increasing attempts to use agent technologies to develop large-scale commercial and industrial software systems. The complexity of such systems suggests a pressing need for system modeling techniques to support reliable, maintainable, and extensible design. G-nets are a type of Petri net defined to support system modeling in terms of a set of independent and loosely-coupled modules. In this paper, we customize the basic G-net model to define a so-called "agent-based G-net" that can serve as a generic model for agent design. Then, to progress from an agent-based design model to an agent-oriented model, new mechanisms to support inheritance modeling are introduced. To illustrate our formal modeling technique for multiagent systems, an example of an agent family in electronic commerce is provided. Finally, we demonstrate how we can use model checking to verify some key behavioral properties of our agent model. This is facilitated by the use of an existing Petri net tool.

Functional Hybrid Modeling

Abstract: The modeling and simulation of physical systems is of key importance in many areas of science and engineering, and thus can benefit from high-quality software tools. In previous research we have demonstrated how functional programming can form the basis of an expressive language for causal hybrid modeling and simulation. There is a growing realization, however, that a move toward non-causal modeling is necessary for coping with the ever increasing size and complexity of modeling problems. Our goal is to combine the strengths of functional programming and non-causal modeling to create a powerful, strongly typed fully declarative modeling language that provides modeling and simulation capabilities beyond the current state of the art. Although our work is still in its very early stages, we believe that this paper clearly articulates the need for improved modeling languages and shows how functional programming techniques can play a pivotal role in meeting this need.

Modeling agent organizations using roles

Abstract: Agent-based and active object systems are no longer contained within the boundaries of a single, small organization. To meet the demands of large-scale software and systems modeling, we need useful analogies for modeling and constructing large-scale systems of autonomous, interactive software entities. In this paper, we employ social and organizational systems theory as a way to guide our understanding of the notion of role and its implications on how agents (and active objects) might behave in group settings.

A Modeling Framework for Network Processor Systems

Abstract: Network processors essentially provide flexible support for communications workloads at high-performance levels. Designing a network processor involve the design and optimization of many component devices and subsystems. It is observed that system modeling can be an economical means of evaluating design alternatives. An effective system models provide a fast and sufficiently accurate description of system performance. This chapter introduces modeling framework for a network processor systems. The framework is composed of independent application, system, and traffic models that describe router functionality, system resources, and packet traffic respectively. The chapter presents several modeling examples of uniprocessor and multiprocessor systems executing internet protocol (IPv4) routing and IP security (IPSec) virtual private network (VPN) encryption or decryption. The framework emphasizes ease of use and utility, and permits users to begin full system analysis of existing or novel applications and systems very quickly. Framework users can also include writing router software, router system architects, or network processor architects.

Architectural Modeling and Analysis of Complex Real-Time Systems

Abstract: Most automation systems and other large industrial software systems have long lifetimes and customers expect these systems to be supported as long as they are in operation Furthermore software components in these systems may be reused in di erent products e g using a soft ware product line approach Hence the lifetime of software in individual systems may be very long several decades or even longer Software that is used for a long time will be exposed to frequent changes as the system evolve over time e g due to adding new function ality error corrections or changing the hardware platform The larger and older the system is the harder it becomes to foresee the consequences of changes In this thesis we present three di erent techniques for managing the evolution of large and complex real time systems The techniques are based on analytical modeling predicting di erent quality properties e g temporal correctness by analyzing a model of the software The rst technique is a component model with analytical interfaces ReFlex that allows us to predict di erent properties of a component assembly the second is a probabilistic modeling language which is analyzed by simu lations ART FW and the third technique is an extension of classical timed automata with a notion of real time tasks TAT Ideally the analytical models should evolve together with the soft ware However since new features are often added and the implemen tation is often changed without updating the model the model becomes obsolete and predictions based on the model are no longer valid By applying the techniques proposed in this thesis we can re introduce an alyzability Using ReFlex we can update the analytical aspects while re designing the system Unless ReFlex has been used in the earlier design this will require a costly redesign of the complete system but consistency between the analytical model and the implementation will be ensured Using ART FW or TAT the implementation will be kept untouched by

Architectural interaction diagrams: AIDs for system modeling

Abstract: This paper develops a modeling paradigm called Architectural Interaction Diagrams, or AIDs, for the high-level design of systems containing concurrent, interacting components. The novelty of AIDs is that they introduce interaction mechanisms, or buses, as first-class entities into the modeling vocabulary. Users then have the capability, in their modeling, of using buses whose behavior captures interaction at a higher level of abstraction than that afforded by modeling notations such as Message Sequence Charts or process algebra, which typically provide only one fixed interaction mechanism. This paper defines AIDs formally by giving them an operational semantics that describes how buses combine subsystem transitions into system-level transitions. This semantics enables AIDs to be simulated; to incorporate subsystems given in different modeling notations into a single system model; and to use testing, debugging and model checking early in the system design cycle in order to catch design errors before they are implemented.

Scale transfer modeling: using emergent computation for coupling an ordinary differential equation system with a reactive agent model

Abstract: This article deals with the coupling of analytical models with individual based models design with the reactive agents paradigm. Such a coupling of models of different natures is motivated by the need to find a way to model scale transfer in large complex systems, i.e. to model how low level of organization can be made to influence upper level and vice versa. This is a fundamental issue, and more particularly in ecological modeling where models are a real scientific tool of investigation. Individuals and populations are not described at the same scale of time and space but it is known that they act on each others. Based on this example, we model individuals in their environment and the population dynamics. While behavior is best modeled using an algorithmic framework (the reactive agent paradigm), population dynamics (because of the number of interacting entities) is best modeled using numerical models. We propose the use of the concept of emergent computation as a framework for coupling heterogeneous formalisms. In the same time, it is crucial to be aware of the consequences of the simplifications and of the choices that are made in the reactive agent model, such as the topology of space and various parameters. In this article, we discuss these issues and our approach on a case study drawn from marine ecology and we show that it is possible to find classical mathematical functional responses with a reactive agent system. Then, we propose a methodology to deal with the coupling of heterogeneous formalism useful in any kind of system modeling.

Grounding systems modeling for high frequencies and transients: some fundamental considerations

Abstract: In spite of large amount of research work in the last decades on the grounding systems modeling for high frequencies and transients there is no consensus on its practica applicability. This work points to some issues that may be important in the systematic approach to determine the validity domains of the different existing methods for analysis. In particular, the following topics are discussed: the evaluation of the upper frequency of interest in the transient study, the limitations due to the electrical dimensions of the system, and due to the underlying circuit concepts, especially in relation to the definition of impedance to ground. As a basis for the evaluation of the validity domains of more simplified quasi-static and circuit based models a full-wave electromagnetic model is described. Validation by comparison with experiment and illustrative numerical results are presented.

Behavior of Smith predictor in teleoperation systems with modeling and delay time errors

Abstract: In this paper, behavior of teleoperation systems with modeling error and error of delay time in Smith predictor is discussed. In teleoperation systems usually there is a large distance between master system and slave system. In this case, there is always an error in modeling of system. The condition for stability of teleoperation systems with modeling error is derived by introducing a theorem. This theorem can assist a designer in ensuring the stability of the teleoperation system. Also, error of delay time and stability of teleoperation systems by using of Internet as communication channel are discussed. The effect of delay time prediction on the system stability and performance is studied and it is shown that delay time prediction could improve system performance. Simulation results are presented to verify the obtained results.

A Direct Modeling Method of the Unbiased GM(1,1)

Abstract: There are some problems in GM( 1,1) modeling, such as, modeling method biased, compatibility condition not satisfied , linear transformation inconsistent and the first number of the initial sequence not functioning in modeling after an accumulated generating operation. In this paper, three grey differential equations are presented and a direct modeling method of the unbiased CM (1,1) is proposed.It is proved that the new method possesses not only white exponential law coincidence property but also linear transformation consistency. The analysis of practical examples show that it improves the modeling precision, enlarges the application scope of the model and makes full use of the first number of the initial sequence.

System Modeling and Robust Control of an AMB Spindle" Part I Modeling and Validation for Robust Control

Abstract: This paper discusses details of modeling and robust control of an AMB (active magnetic bearing) spindle, and part I presents a modeling and validation process of the AMB spindle. There are many components in AMB spindle : electromagnetic actuator, sensor, rotor, power amplifier and digital controller. If each component is carefully modeled and evaluated, the components have tight structured uncertainty bounds and achievable performance of the system increases. However, since some unknown dynamics may exist and the augmented plant could show some discrepancy with the real plant, the validation of the augmented plant is needed through measuring overall frequency responses of the actual plant. In addition, it is necessary to combine several components and identify them with a reduced order model. First, all components of the AMB spindle are carefully modeled and identified based on experimental data, which also render valuable information in quantifying structured uncertainties. Since sensors, power amplifiers and discretization dynamics can be considered as time delay components, such dynamics are combined and identified with a reduced order. Then, frequency responses of the open-loop plant are measured through closed-loop experiments to validate the augmented plant. The whole modeling process gives an accurate nominal model of a low order for the robust control design.

Analysing internet software retrieval systems: modeling and performance comparison

Abstract: Nowadays, there exist web sites that allow users to retrieve and install software in an easy way. The performance of these sites may be poor if they are used in wireless networks; the reason is the inadequate use of the net resources that they need. If these kinds of systems are designed using mobile agent technology the previous problem might be avoided. In this paper, we present a comparison between the performance of a software retrieval system especially designed to be used in a wireless network and the performance of a software retrieval system similar to the well-known Tucows.com web site. In order to compare performance, we make use of a software performance process enriched with formal techniques. The process has as important features that it uses UML as a design notation and it uses stochastic Petri nets as formal model. Petri nets provide a formal semantics for the system and a performance model.

CMAC neural network as an SVM with B-spline kernel functions

Abstract: In measurement systems, there is an often need Cerebellar Model Articulation Controller (CMAC) neural network has some attractive features. The most important ones are its extremely fast learning capability and the special architecture that lets effective digital hardware implantation possible. All these properties may be important in measurement systems, e.g. in system modeling or in complex sensor's system, etc. Although the CMAC architecture was proposed in the middle of the seventies, several open questions have been left even for today. Among them the most important ones are about its modeling and generalization capabilities. The limits of fits modeling capability were addressed in the literature and recently a detailed analysis of its generalization properties was given. The results show that there are significant differences between the one-dimensional and the multidimensional versions of CMAC. The modeling capability of a multidimensional network is inferior to that of the one-dimensional one. This paper discusses the reasons of this difference and suggests a new interpretation of CMAC. This interpretation is based on kernel machines. The paper shows that a one-dimensional binary CMAC can be considered as a kernel machine with linear B-spline kernel function. However, this close relation cannot be found in multidimensional case. The paper proposes a version of multidimensional CMAC, which - similarly to the one-dimensional case - can be considered as a kernel machine. The paper introduces this interpretation and details its most important advantages.

A Survey of Modeling Approaches forEmbedded Computer Control Systems

Abstract: The development of embedded computer control systems(ECS) requires a synergetic integration of heterogeneoustechnologies and multiple engineering disciplines. Withincreasing amount of functionalities and expectations for highproduct qualities, short time-to-market, and low cost, thesuccess of complexity control and built-in flexibility turn outto be one of the major competitive edges for many ECS products.For this reason, modeling and modularity assessment constitutetwo critical subjects of ECS engineering.In the development ofECS, model-based design is currently being exploited in most ofthe sub-systems engineering activities. However, the lack ofsupport for formalization and systematization associated withthe overall systems modeling leads to problems incomprehension, cross-domain communication, and integration oftechnologies and engineering activities. In particular, designchanges and exploitation of "components" are often risky due tothe inability to characterize components' properties and theirsystem-wide contexts. Furthermore, the lack of engineeringtheories for modularity assessment in the context of ECS makesit difficult to identify parameters of concern and to performearly system optimization. This thesis aims to provide a more complete basis for theengineering of ECS in the areas of systems modeling andmodularization. It provides solution domain models for embeddedcomputer control systems and the software subsystems. Thesemeta-models describe the key system aspects, design levels,components, component properties and relationships with ECSspecific semantics. By constituting the common basis forabstracting and relating different concerns, these models willalso help to provide better support for obtaining holisticsystem views and for incorporating useful technologies fromother engineering and research communities such as to improvethe process and to perform system optimization. Further, amodeling framework is derived, aiming to provide a perspectiveon the modeling aspect of ECS development and to codifyimportant modeling concepts and patterns. In order to extendthe scope of engineering analysis to cover flexibility relatedattributes and multi-attribute tradeoffs, this thesis alsoprovides a metrics system for quantifying componentdependencies that are inherent in the functional solutions.Such dependencies are considered as the key factors affectingcomplexity control, concurrent engineering, and flexibility.The metrics system targets early system-level design and takesinto account several domain specific features such asreplication and timing accuracy. Keywords:Domain-Specific Architectures, Model-basedSystem Design, Software Modularization and Components, QualityMetrics.

Tangible Toolkits for Reflective Systems Modeling

Abstract: Understanding dynamic systems is an important but difficult task across a wide range of disciplines. Building such intuitions is particularly difficult for novices, for whom traditional representations of systems models are often opaque and confusing. Yet these novices often have deep, situated knowledge that is crucial to building powerful models. This thesis leverages work in the field of tangible interfaces to create an infrastructure for building domain-specific toolkits for models of dynamic systems that are transparent and actively support collaboration in their use. We report on two case studies for which we built toolkits based on this infrastructure. Drawing on these studies, we develop criteria for the design of toolkits that provide support for reflection by novices and experts alike. We further outline a framework for the effective use of reflective systems modeling in both academic and corporate settings. Thesis Supervisor: Bakhtiar Mikhak Research Scientist, MIT Media Lab

Modeling and analysis of power-aware systems

Abstract: The paper describes a formal approach for designing and reasoning about power-constrained, timed systems. The framework is based on process algebra, a formalism that has been developed to describe and analyze communicating concurrent systems. The proposed extension allows the modeling of probabilistic resource failures, priorities of resource usages, and power consumption by resources within the same formalism. Thus, it is possible to model alternative power-consumption behaviors and analyze tradeoffs in their timing and other characteristics. This paper describes the modeling and analysis techniques, and illustrates them with examples, including a dynamic voltage-scaling algorithm.

Modeling of Dynamically Modifiable Embedded Real-Time Systems

Abstract: In the paper a Petri net based approach for modeling dynamically modifiable embedded real-time systems is presented The presented work contributes to the extension of a Petri net based design methodology for distributed embedded systems towards the handling of dynamically modifiable systems Extensions to the underlying High-Level Petri net model are introduced that allow for dynamic modifications of a net at run-time Furthermore, a simulation tool for the resulting self-modifying net model is outlined The tool has been designed to simulate the execution of a dynamically modifying Petri net on a simplified model of a hardware platform which is dynamically modifying as well

Power system modelling using hybrid system theory

Abstract: This paper describes the power system hybrid interactive behavior of continuous dynamic and the discrete event dynamic, and introduces programmable timed Petri Nets modeling tools of hybrid system. The paper proposes hybrid power system modeling method using programmable timed Petri Nets. The method divides complex power system into discrete state logic layer and continuous state layer. A high-level discrete events supervisory is used to coordinate the actions of the action of various subsystem. Meantime, the paper gives a modeling example of power system with OLTC, and analysis of power system logic switching stability using multiple Lyapunov functions. Simulation results denote that the model switching is stable and the proposed hybrid modeling method is feasible.

WebML+: a Web modeling language for forming a bridge between business modeling and information modeling.

Abstract: One aspect of the development of Web-enabled systems that has received increasing attention is information modeling, particularly with respect to aspects such as navigation and content models. These models have however typically focused on modeling at a relatively low-level and have failed to address higher-level aspects, such as architectural and business process modeling. We have proposed WebML+, a set of formal extensions to an existing modeling language (WebML), which is able to form a bridge between higher level business models and lower level detailed designs. In this paper we provide guidelines for supporting the derivation of a WebML+ model from/to these different models, thereby providing a concrete link between them. We illustrate these guidelines with a detailed example.

Simulation of Engine Systems in Modelica

Abstract: This paper details the use of the Modelica modeling language for the simulation of engine systems. The first part of the paper briefly outlines some of the challenging, multi-domain components of engine system modeling and is followed by a discussion of some of the connectors, interfaces, and model templates that enable robust, efficient model development. The remainder of the paper presents selected modeling examples with particular attention to the structure and implementation of the models that promotes model flexibility and re-use.

Functional Modeling of Complex Mechatronic Systems

Abstract: In this paper, we present a systematic approach for functional modeling of complex mechatronic systems. This approach is built upon our modeling representation platform dedicated to mechatronic systems. In particular, this approach is structured to span the functional modeling process through five phases: function generation, function decomposition, function analysis, function transformation, and structure refinement. By means of functional modeling, a function structure of the mechatronic system under design can be created upon which the formation of design concepts and solutions can be further built. Application of this approach to the conceptual design of a parallel robotic device is illustrated along with discussions.Copyright © 2003 by ASME

Towards Object-Oriented Graphs and Grammars

Abstract: This work aims to extend the algebraical approach to graph transformation to model object-oriented systems structures and computations. A graph grammar based formal framework for object-oriented system modeling is presented, incorporating both the static aspects of system modeling and the dynamic aspects of computation of object-oriented programs.

Flexible Modeling and Simulation for Mass Customization Manufacturing

Abstract: Mass Customization Manufacturing (MCM) systems possess special characteristics that make the modeling of such systems extremely difficult. These characteristics include concurrency, synchronization, and cooperation among subsystems. To support the development and analysis of these systems, new approaches to modeling and simulation must be developed. In this paper, an architecture for a modeling and simulation platform to support MCM is presented. The platform can represent solutions to problems such as dynamic rescheduling, shop reconfiguration, and multi-robot cooperation and coordination.