Showing papers on "Modeling and simulation published in 2012"

Modeling Cyber–Physical Systems

Abstract: This paper focuses on the challenges of modeling cyber-physical systems (CPSs) that arise from the intrinsic heterogeneity, concurrency, and sensitivity to timing of such systems. It uses a portion of an aircraft vehicle management system (VMS), specifically the fuel management subsystem, to illustrate the challenges, and then discusses technologies that at least partially address the challenges. Specific technologies described include hybrid system modeling and simulation, concurrent and heterogeneous models of computation, the use of domain-specific ontologies to enhance modularity, and the joint modeling of functionality and implementation architectures.

On the Switching Parameter Variation of Metal-Oxide RRAM—Part I: Physical Modeling and Simulation Methodology

Abstract: The variation of switching parameters is one of the major challenges to both the scaling and volume production of metal-oxide-based resistive random-access memories (RRAMs). In this two-part paper, the source of such parameter variation is analyzed by a physics-based simulator, which is equipped with the capability to simulate a large number ( ~1000) of cyclic SET-RESET operations. By comparing the simulation results with experimental data, it is found that the random current fluctuation experimentally observed in the RESET processes is caused by the competition between trap generation and recombination, whereas the variation of the high resistance states and the tail bits are directly correlated to the randomness of the trap dynamics. A combined strategy with a bilayer dielectric material and a write-verification technique is proposed to minimize the resistance variation. We describe the simulation methodology and discuss the dc results in Part I. The corroboration of the model and the device optimization strategy will be discussed in Part II.

A Simple Approach to Modeling and Simulation of Photovoltaic Modules

Abstract: An accurate model is essential when designing photovoltaic (PV) systems. PV models rely on a set of transcendental nonlinear equations which add to the model complexity. This letter proposes a simple and easy-to-model approach for implementation in simulations of PV systems. It takes advantage of the simplicity of ideal models and enhances the accuracy by deriving a mathematical representation, capable of extracting accurate estimates of the model parameters, directly related to manufacturer datasheets. Experimental measurements proved the effectiveness of the proposed approach.

URDME: a modular framework for stochastic simulation of reaction-transport processes in complex geometries

Abstract: Experiments in silico using stochastic reaction-diffusion models have emerged as an important tool in molecular systems biology. Designing computational software for such applications poses several challenges. Firstly, realistic lattice-based modeling for biological applications requires a consistent way of handling complex geometries, including curved inner- and outer boundaries. Secondly, spatiotemporal stochastic simulations are computationally expensive due to the fast time scales of individual reaction- and diffusion events when compared to the biological phenomena of actual interest. We therefore argue that simulation software needs to be both computationally efficient, employing sophisticated algorithms, yet in the same time flexible in order to meet present and future needs of increasingly complex biological modeling. We have developed URDME, a flexible software framework for general stochastic reaction-transport modeling and simulation. URDME uses U nstructured triangular and tetrahedral meshes to resolve general geometries, and relies on the R eaction-D iffusion M aster E quation formalism to model the processes under study. An interface to a mature geometry and mesh handling external software (Comsol Multiphysics) provides for a stable and interactive environment for model construction. The core simulation routines are logically separated from the model building interface and written in a low-level language for computational efficiency. The connection to the geometry handling software is realized via a Matlab interface which facilitates script computing, data management, and post-processing. For practitioners, the software therefore behaves much as an interactive Matlab toolbox. At the same time, it is possible to modify and extend URDME with newly developed simulation routines. Since the overall design effectively hides the complexity of managing the geometry and meshes, this means that newly developed methods may be tested in a realistic setting already at an early stage of development. In this paper we demonstrate, in a series of examples with high relevance to the molecular systems biology community, that the proposed software framework is a useful tool for both practitioners and developers of spatial stochastic simulation algorithms. Through the combined efforts of algorithm development and improved modeling accuracy, increasingly complex biological models become feasible to study through computational methods. URDME is freely available at http://www.urdme.org .

Spatial modeling of cell signaling networks.

Abstract: The shape of a cell, the sizes of subcellular compartments and the spatial distribution of molecules within the cytoplasm can all control how molecules interact to produce a cellular behavior. This chapter describes how these spatial features can be included in mechanistic mathematical models of cell signaling. The Virtual Cell computational modeling and simulation software is used to illustrate the considerations required to build a spatial model. An explanation of how to appropriately choose between physical formulations that implicitly or explicitly account for cell geometry and between deterministic vs, stochastic formulations for molecular dynamics is provided, along with a discussion of their respective strengths and weaknesses. As a first step toward constructing a spatial model, the geometry needs to be specified and associated with the molecules, reactions and membrane flux processes of the network. Initial conditions, diffusion coefficients, velocities and boundary conditions complete the specifications required to define the mathematics of the model. The numerical methods used to solve reaction-diffusion problems both deterministically and stochastically are then described and some guidance is provided in how to set up and run simulations. A study of cAMP signaling in neurons ends the chapter, providing an example of the insights that can be gained in interpreting experimental results through the application of spatial modeling.

Engineering Principles of Combat Modeling and Distributed Simulation

Abstract: Explore the military and combat applications of modeling and simulationEngineering Principles of Combat Modeling and Distributed Simulation is the first book of its kind to address the three perspectivesthat simulation engineers must master for successful military and defense related modeling: the operational view (what needs to be modeled); the conceptual view (how to do combat modeling); and the technical view (how to conduct distributed simulation). Through methods from the fields of operations research, computer science, and engineering, readers are guided through the history, current training practices, and modern methodology related to combat modeling and distributed simulation systems. Comprised of contributions from leading international researchers and practitioners, this book provides a comprehensive overview of the engineering principles and state-of-the-art methods needed to address the many facets of combat modeling and distributed simulation and features the following four sections:Foundations introduces relevant topics and recommended practices, providing the needed basis for understanding the challenges associated with combat modeling and distributed simulation.Combat Modeling focuses on the challenges in human, social, cultural, and behavioral modeling such as the core processes of "move, shoot, look, and communicate" within a synthetic environment and also equips readers with the knowledge to fully understand the related concepts and limitations.Distributed Simulation introduces the main challenges of advanced distributed simulation, outlines the basics of validation and verification, and exhibits how these systems can support the operational environment of the warfighter.Advanced Topics highlights new and developing special topic areas, including mathematical applications fo combat modeling; combat modeling with high-level architecture and base object models; and virtual and interactive digital worlds.Featuring practical examples and applications relevant to industrial and government audiences, Engineering Principles of Combat Modeling and Distributed Simulation is an excellent resource for researchers and practitioners in the fields of operations research, military modeling, simulation, and computer science. Extensively classroom tested, the book is also ideal for courses on modeling and simulation; systems engineering; and combat modeling at the graduate level.

Black-Box Modeling of Three-Phase Voltage Source Inverters for System-Level Analysis

Abstract: Modeling and simulation are powerful tools to design power distribution systems made up of multiple converters and loads, such as the system of the more-electric aircraft (MEA). However, a system designer usually has no access to detailed data of the power converters, due to confidentiality of manufacturers. Therefore, a black-box modeling approach is necessary. This paper proposes a large-signal black-box modeling technique of three-phase voltage source inverters. The resulting model is oriented to perform system-level analysis and is fully parameterized from the transient response of the converter, which is obtained through simple experimental tests based on low-cost equipment. Moreover, it does not represent the internal data of the converter, thus keeping the confidentiality of the manufacturer. The proposed method has been experimentally validated on a 5-kW actual inverter, which has been applied on the test bench of an MEA power distribution system.

Modeling and simulation of ion transport in dielectric liquids - Fundamentals and review

Abstract: This review paper introduces fundamental knowledge about and presents recent developments in modeling and simulation of ion transport and electrohydrodynamic flow in dielectric liquids. Starting with the formulation of the governing equations, we introduce background ideas as well as the related modeling of ion dissociation, recombination, injection, and discharge, which play key roles in the charge creation and transport problem. Numerical methods and solutions are then presented for the onedimensional problem over the domain between a pair of parallel electrodes. In particular, we show how the electrical properties of a nonpolar liquid, m-xylene, can be derived from the matching of the numerical solutions with Novotny's experimental data. Two asymptotic solution methods, one for the overlap-layer and the other for the thin-layer regimes, are then presented; in particular, we show a remarkably high accuracy for the solutions. The current-voltage relation with ion dissociation and recombination is shown to be completely different from that without them. A historical review of the modeling and simulation of ion transport and electrohydrodynamic flow is finally touched upon.

Recent Progress in Modeling, Simulation, and Optimization of Polymer Solar Cells

Abstract: The power conversion efficiency of polymer solar cells today has passed 10%, the commonly acceptable value for commercial usage. However, in general labs, the power conversion efficiency routinely achievable is only at 3–5% because of the lack of effective tools to optimize the device design and the fabrication process. Instead of using trial-and-error experiments to improve the power efficiency, modeling and simulation provides an alternative, effective, and economical way to optimize the design of polymer solar cells for best device performance. This review gives a literature survey, including some of our own studies, on modeling and simulation of polymer solar cells. First, the fundamentals of polymer solar cells are briefly explained. Then, the optical and electrical modeling and simulation are discussed in detail, followed by a discussion on optimization of polymer solar cells via modeling and simulation. This review ends with an outlook for the future study on modeling, simulation, and optimization of polymer solar cells.

Guide to Modeling and Simulation of Systems of Systems

Abstract: This guide demonstrates how virtual build and test can be supported by the Discrete Event Systems Specification (DEVS) simulation modeling formalism, and the System Entity Structure (SES) simulation model ontology. The book examines a wide variety of Systems of Systems (SoS) problems, ranging from cloud computing systems to biological systems in agricultural food crops. Features: includes numerous exercises, examples and case studies throughout the text; presents a step-by-step introduction to DEVS concepts, encouraging hands-on practice to building sophisticated SoS models; illustrates virtual build and test for a variety of SoS applications using both commercial and open source DEVS simulation environments; introduces an approach based on activity concepts intrinsic to DEVS-based system design, that integrates both energy and information processing requirements; describes co-design modeling concepts and methods to capture separate and integrated software and hardware systems.

Modeling and simulation based approach of photovoltaic system in simulink model

Abstract: This paper presents the modeling and simulation of photovoltaic model using MATLAB/Simulink software package. The proposed model is design with a user-friendly icon using Simpower of Simulink block libraries. Taking the effect of irradiance and temperature into consideration, the output current and power characteristic of PV model are simulated using the proposed model. Detailed modeling procedure for the circuit model with numerical values is presented. The simulator is verified by applying the model to 36 W PV modules. The proposed model was found to be better and accurate for any irradiance and temperature variations. The proposed model can be very useful for PV Engineers and expert who require a simple, fast and accurate PV simulator to design their systems.

Modeling and Simulation of Microwave Heating of Foods Under Different Process Schedules

Abstract: This paper describes the development of a simulation model for heating of foods in microwave ovens and its uses to optimize food heating strategies. The solution of the coupled energy and mass microscopic balances considers the electromagnetic energy absorption as well as temperature-dependent thermal, transport, and dielectric properties. The microscopic balances are highly nonlinear coupled differential equations, which were solved using finite element software (Comsol Multiphysics). Maxwell equations were employed in order to describe the interaction between electromagnetic radiation and food. The mathematical model allowed the evaluation of the effect of product size and composition in the temperature profiles that developed inside the food that was radiated either on one or both sides. In order to improve the nonuniform temperature profiles that occurred within foods under continuous operation, different operation schemes were evaluated: intermittent cycles, joint action of microwaves with air impingement, and the effect of interference of electromagnetic waves.

Modeling and simulation of equivalent circuits in description of biological systems - a fractional calculus approach

Abstract: Using the fractional calculus approach, we present the Laplace analysis of an equivalent electrical circuit for a multilayered system, which includes distributed elements of the Cole model type. The Bode graphs are obtained from the numerical simulation of the corresponding transfer functions using arbitrary electrical parameters in order to illustrate the methodology. A numerical Laplace transform is used with respect to the simulation of the fractional differential equations. From the results shown in the analysis, we obtain the formula for the equivalent electrical circuit of a simple spectrum, such as that generated by a real sample of blood tissue, and the corresponding Nyquist diagrams. In addition to maintaining consistency in adjusted electrical parameters, the advantage of using fractional differential equations in the study of the impedance spectra is made clear in the analysis used to determine a compact formula for the equivalent electrical circuit, which includes the Cole model and a simple RC model as special cases.

Modeling and simulation of a microgrid as a Stochastic Hybrid System

Abstract: Microgrids (MGs) are small-scale local energy grids. While dedicated to cover local power needs, their structure and operation is usually quite complex. Complexity arises due to a number of factors: in the first instance, a variety of operational modes - among them, MGs can be considered to be operated autonomously whenever the main distribution grid is not available; furthermore, the heterogeneity of energy types in a MG - not exclusively electrical energy, but also thermal for instance; also, the different functions that a MG energy management system has to fulfill - like coordination and dispatching of multiple generation, transfer, transformation and storage devices; finally, the external and internal random factors that affect operations. All these aspects make control and scheduling of a MG quite a challenging task. On the other hand, this widespread complexity leaves much room for improvement on the current state of the art. An advancement on the state of the art requires the development of a realistic model of the system at hand. This work puts forward a model of a MG that is based on the framework of Stochastic Hybrid Systems (SHS). SHS models can capture the interaction between probabilistic elements and discrete and continuous dynamics, and thus promise to be able to tame the complexity of the systems discussed above. This work displays the outcomes of model simulations and discusses potential development of general analysis and synthesis approaches over SHS models (e.g., based on model checking and on approximate dynamic programming) for typical challenges in MGs.

Hybrid modeling and simulation of stochastic effects on progression through the eukaryotic cell cycle

Abstract: The eukaryotic cell cycle is regulated by a complicated chemical reaction network. Although many deterministic models have been proposed, stochastic models are desired to capture noise in the cell resulting from low numbers of critical species. However, converting a deterministic model into one that accurately captures stochastic effects can result in a complex model that is hard to build and expensive to simulate. In this paper, we first apply a hybrid (mixed deterministic and stochastic) simulation method to such a stochastic model. With proper partitioning of reactions between deterministic and stochastic simulation methods, the hybrid method generates the same primary characteristics and the same level of noise as Gillespie's stochastic simulation algorithm, but with better efficiency. By studying the results generated by various partitionings of reactions, we developed a new strategy for hybrid stochastic modeling of the cell cycle. The new approach is not limited to using mass-action rate laws. Numerical experiments demonstrate that our approach is consistent with characteristics of noisy cell cycle progression, and yields cell cycle statistics in accord with experimental observations.

Real-Time Simulation Technologies : Principles, Methodologies, and Applications

Abstract: Section I: Basic Simulation Technologies and Fundamentals Real-Time Simulation Using Hybrid Models, R. Crosbie Formalized Approach for the Design of Real-Time Distributed Computer Systems, M. Zhang, B. Zeigler, and X. Hu Principles of DEVS Model Verification for Real-Time Embedded Applications, H. Saadawi, G.A. Wainer, and M. Moallemi Optimizing Discrete Modeling and Simulation for Real-Time Constraints with Metaprogramming, L. Touraille, J. Caux, and D. Hill Modeling with UML and Its Real-Time Profiles, E. Farcas, I.H. Kruger, and M. Menarini Modeling and Simulation of Timing Behavior with the Timing Definition Language, J. Templ, A. Naderlinger, P. Derler, P. Hintenaus, W. Pree, and S. Resmerita Section II: Real-Time Simulation for System Design Progressive Simulation-Based Design for Networked Real-Time Embedded Systems, X. Hu and E. Azarnasab Validator Tool Suite: Filling the Gap between Conventional Software-in-the-Loop and Hardware-in-the-Loop Simulation Environments, S. Resmerita, P. Derler, W. Pree, and K. Butts Modern Methodology of Electric System Design Using Rapid-Control Prototyping and Hardware-in-the-Loop, J. Belanger and C. Dufour Modeling Multiprocessor Real-Time Systems at Transaction Level, G. Beltrame, G.Nicolescu, and L. Fossati Service-Based Simulation Framework for Performance Estimation of Embedded Systems, A. Sejer Tranberg-Hansen and J. Madsen Consistency Management of UML Models, E. Farcas, I.H. Kruger, and M. Menarini Section III: Parallel and Distributed Real-Time Simulation Interactive Flight Control System Development and Validation with Real-Time Simulation, H.H. T. Liu Test Bed for Evaluation of Power Grid Cyber-Infrastructure, D.C. Bergman and D.M. Nicol System Approach to Simulations for Training: Instruction, Technology, and Process Engineering, S.Schatz, D. Nicholson, and R. Dolletski Concurrent Simulation for Online Optimization of Discrete Event Systems, C.G. Cassandras and C.G. Panayiotou Section IV: Tools and Applications Toward Accurate Simulation of Large-Scale Systems via Time Dilation, J. Edmondson and D.C. Schmidt Simulation for Operator Training in Production Machinery, G. Rath Real-Time Simulation Platform for Controller Design, Test, and Redesign, S. Sahin, Y. Isler, and C. Guzelis Automotive Real-Time Simulation: Modeling and Applications, J. Scharpf, R. Hopler, and J. Hillyard Specification and Simulation of Automotive Functionality Using AUTOSAR, M. Di Natale Modelica as a Platform for Real-Time Simulation, J.J. Batteh, M.M. Tiller, and D. Winkler Real-Time Simulation of Physical Systems Using Simscape(TM), S. Miller and J. Wendlandt Systematic Derivation of Hybrid System Models for Hydraulic Systems, J. Hodgson, R. Hyde, and S. Sharma

Modeling and simulation of wind-PV hybrid power system using Matlab/Simulink

Abstract: This paper presents the modeling of a PV-wind hybrid system in Matlab/Simulink. The model is useful for simulation of a hybrid PV-wind system connected to a grid. Blocks like wind model, PV model, energy conversion and load are implemented and the results of simulation are also presented. The behavior of hybrid system employing renewable and variable in time energy sources while providing a continuous supply. Application represents a useful tool in research activity and also in teaching.

Fundamentals of Higher Order Neural Networks for Modeling and Simulation

Abstract: In this chapter, the authors provide fundamental principles of Higher Order Neural Units (HONUs) and Higher Order Neural Networks (HONNs) for modeling and simulation. An essential core of HONNs can be found in higher order weighted combinations or correlations between the input variables and HONU. Except for the high quality of nonlinear approximation of static HONUs, the capability of dynamic HONUs for the modeling of dynamic systems is shown and compared to conventional recurrent neural networks when a practical learning algorithm is used. In addition, the potential of continuous dynamic HONUs to approximate high dynamic order systems is discussed, as adaptable time delays can be implemented. By using some typical examples, this chapter describes how and why higher order combinations or correlations can be effective for modeling of systems. Zeng-Guang Hou The Chinese Academy of Sciences, China

Constant-Parameter $RL$ -Branch Equivalent Circuit for Interfacing AC Machine Models in State-Variable-Based Simulation Packages

Abstract: Transient simulation programs, either nodal analysis-based electromagnetic transient program (EMTP-like) or state-variable-based, are used very extensively for modeling and simulation of various power and energy systems with electrical machines. It has been shown in the literature that the method of interfacing machine models with the external electrical network plays an important role in numerical accuracy and computational performance of the overall simulation. This paper considers the state-variable-based simulation packages, and provides a constant-parameter decoupled RL-branch equivalent circuit for interfacing the ac induction and synchronous machine models with the external electrical network. The proposed interfacing circuit is based on the voltage-behind-reactance formulation which has been shown to have advantageous properties. For the synchronous machines, this paper describes both implicit and explicit (approximate) interfacing methods. The presented case studies demonstrate the advantages of using the proposed interfacing method over the traditional -models that are conventionally used in many simulation packages.

Modeling and simulation of photovoltaic cell/module/array with two-diode model

Abstract: The purpose of this paper is to propose a MATLAB/ Simulink simulators for PV cell/module/array based on the Two-diode model of a PV cell.This model is known to have better accuracy at low irradiance levels which allows for more accurate prediction of PV systems performance.To reduce computational time , the input parameters are reduced as the values of Rs and Rp are estimated by an efficient iteration method. Furthermore ,all of the inputs to the simulators are information available on a standard PV module datasheet. The present paper present first abrief introduction to the behavior and functioning of a PV device and write the basic equation of the two-diode model,without the intention of providing an indepth analysis of the photovoltaic phenomena and the semicondutor physics. The introduction on PV devices is followed by the modeling and simulation of PV cell/PV module/PV array, which is the main subject of this paper. A MATLAB Simulik based simulation study of PV cell/PV module/PV array is carried out and presented .The simulation model makes use of the two-diode model basic circuit equations of PV solar cell, taking the effect of sunlight irradiance and cell temperature into consideration on the output current I-V characteristic and output power P-V characteristic . A particular typical 50W solar panel was used for model evaluation. The simulation results , compared with points taken directly from the data sheet and curves pubblished by the manufacturers, show excellent correspondance to the model.

Modeling and simulation of directly driven wind turbine with permanent magnet synchronous generator

Abstract: Wind energy, a kind of renewable and clean energy, is widely studied nowadays. Directly driven wind turbine permanent magnet synchronous generator (D-PMSG) plays an important role in the modern wind generating systems. A reliable and speedy simulation of the wind directly driven permanent-magnet synchronous generator is significant. By replacing the power electronic device with math equivalence, it established the windmill model, PMSG model, control model, voltage source converter (VSC) model, dc-line model, filter model and grid model in this paper. It achieved a simulation in Simulink of Matlab. This simulation model could fix the aim of maximum wind energy tracking, active power and reactive power independent control and variable speed constant frequency operation. With the influence of wind speed changing and short circuit occurring, the simulation results show the availability of the control strategies and research.