Showing papers on "Modeling and simulation published in 1999"

A Matlab-based modeling and simulation package for electric and hybrid electric vehicle design

Abstract: This paper discusses a simulation and modeling package developed at Texas A&M University, V-Elph 2.01. V-Elph facilitates in-depth studies of electric vehicle (EV) and hybrid EV (HEV) configurations or energy management strategies through visual programming by creating components as hierarchical subsystems that can be used interchangeably as embedded systems. V-Elph is composed of detailed models of four major types of components: electric motors, internal combustion engines, batteries, and support components that can be integrated to model and simulate drive trains having all electric, series hybrid, and parallel hybrid configurations. V-Elph was written in the Matlab/Simulink graphical simulation language and is portable to most computer platforms. This paper also discusses the methodology for designing vehicle drive trains using the V-Elph package. An EV, a series HEV, a parallel HEV, and a conventional internal combustion engine (ICE) driven drive train have been designed using the simulation package. Simulation results such as fuel consumption, vehicle emissions, and complexity are compared and discussed for each vehicle.

Test systems for harmonics modeling and simulation

Abstract: This paper presents three harmonic simulation test systems. The purpose is to demonstrate guidelines for the preparation and analysis of harmonic problems through case studies and simulation examples. The systems can also be used as benchmark systems for the development of new harmonic simulation methods and for the evaluation of existing harmonic analysis software.

A New Methodology for the Estimation of Total Uncertainty in Computational Simulation

Abstract: INTRODUCTION This paper develops a general methodology for estimating the total uncertainty in computational simulations that deal with the numerical solution of a system of partial differential equations. A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of -the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. In each of these phases, general sources of variability, uncertainty, and error are identified. Our general methodology is applicable to any discretization procedure for solving ordinary or partial differential equations. To demonstrate this methodology, we describe a system-level analysis of an unguided, rocket-boosted, aircraft-launched missile. In the conceptual modeling phase, a wide variety of analysis options are considered, but only one branch of the analysis is computed: rigid body flight dynamics. We choose two parameters as nondeterministic elements of the system: one has variability that is treated probabilistically and one has uncertainty that is represented as a set of possible alternatives. To illustrate mathematical modeling uncertainty, we pursue two models with differing levels of physics: a six-degree-of-freedom and a three-degree-of- freedom model. We also examine numerical solution error in the analysis, which is ubiquitous in computational simulations. Historically the primary method of evaluating the performance of a proposed system design has been to build the design and then test it in the use environment. This testing process is often iterative, as design flaws are sequentially discovered and corrected. The number of design-test iterations has been reduced with the advent of computer simulation through numerical solution of the mathematical equations describing the system behavior. Computational results can identify some flaws and they avoid the difficulty or safety issues involved in conducting certain types of physical tests. Examples include the atmospheric entry of a space probe into another planet, structural failure of a full-scale containment vessel of a nuclear power plant, failure of a bridge during an earthquake, and exposure of a nuclear weapon to certain types of accident environments. Modeling and simulation are valuable tools in assessing the survivability and vulnerability of complex systems to either natural, abnormal, and hostile events. However, there still remains the need to assess the accuracy of simulations by comparing computational predictions with experimental test data through the process known as validation of computational simulations. Experimental validation, however, is continually increasing in cost and time rcquircd to conduct the test. For these reason modeling and simulation must take increasing responsibility for the safety, performance, and reliability of many high consequence systems.

Activity-based construction (abc) modeling and simulation method

Abstract: This research presents the activity-based construction (ABC) modeling and simulation method. ABC modeling (ABC-Mod) uses one single element (e.g., activity) for modeling general construction proces...

Efficient techniques for accurate modeling and simulation of substrate coupling in mixed-signal IC's

Abstract: Industry trends aimed at integrating higher levels of circuit functionality have triggered a proliferation of mixed analog-digital systems. Magnified noise coupling through the common chip substrate has made the design and verification of such systems an increasingly difficult task. In this paper we present a fast eigendecomposition technique that accelerates operator application in BEM methods and avoids the dense-matrix storage while taking all of the substrate boundary effects into account explicitly. This technique can be used for accurate and efficient modeling of substrate coupling effects in mixed-signal integrated circuits.

Advances in modeling and simulation of vacuum electronic devices

Abstract: Recent advances in the modeling and simulation of vacuum electronic devices are reviewed. Design of these devices makes use of a variety of physical models and numerical code types. Progress in the development of these models and codes is outlined and illustrated with specific examples. The state of the art in device simulation is evolving to the point such that devices can be designed on the computer, thereby eliminating many trial and error fabrication and test steps. The role of numerical simulation in the design places can be expected to grow further in the future.

Modeling and Simulation of an Electric Arc Furnace Process

Abstract: The model derived in this paper is intended for the testing of control strategies using off-gas variables in the control of an Electric Arc Furnace (EAF). The derivation of a multivariable non-linear state space model of an EAF process is treated. Assumptions are made that facilitate the modeling effort. First principles of thermodynamics, together with empirical relationships, are used to derive the model equations. A state-space model is developed with physical variables such as carbon content in the steel as model states. Rates of change such as decarburization are also considered. Typical operating conditions for a furnace are discussed and initial conditions for a simulation are derived from this. A timeline of events corresponding to operating conditions is determined for the simulation. A simulation is conducted starting with the initial conditions and proceeding with the line of events. The results of the simulation are shown and discussed in terms of the purpose of the model.

Optimal design of automotive hybrid powertrain systems

Abstract: Alternative powertrains for automotive applications aim at improving emissions and fuel economy. Lack of experience with these relatively new technologies makes them ideal applications for computer-based modeling and simulation studies. There is a variety of configurations, control strategies, and design variable choices that can be made. If mathematical models exist, rigorous optimization techniques can be used to explore the design space. This paper provides an overview of a design environment for alternative powertrains that has these characteristics: modularity, allowing a system to be built by combining components; flexibility allowing different levels of fidelity and different existing codes to be used; and, rigor, since it is based an mathematical methods of decision making. A simple application to a hybrid diesel-electric powertrain is included.

Comparison of coupled and decoupled solutions for temperature and air flow in a building

Abstract: This paper concerns modeling and simulation of coupled heat and air flow in buildings. A brief overview of the current state in modeling this issue is included. Starting from a zonal mass balance approach, the paper describes a method used for the simultaneous solution of the associated nonlinear equations, and the solution coupling of the heat and mass conservation equation sets. By means of a case study involving a case of strongly coupled heat and air flow, this paper aims to quantify the differences - in terms of accuracy and computer resources - resulting from coupled and decoupled solution methods. The main conclusion from the case study is that the coupled solution method will be able to generate accurate results, even with simulation time steps of one hour. Reducing the time step will increase the computing resources used considerably, with a relatively small improvement in the accuracy. For equal length of time step a coupled solution method will use more computer resources than a decoupled solution. In the case of the decoupled method it is necessary to reduce the time step, to ensure the accuracy. For the current case study, the decoupled solution method using a simulation time step of 360 s was less accurate than the coupled solution method with a time step of one hour. However the computer resources used were more than double. Based on the case study it may be concluded that the coupled solution gives the best overall results in terms of both accuracy and computer resources used.

Computer-Aided Modeling and Simulation of Active Power Filters

Abstract: This paper deals with the computer-based modeling and simulation of active power filters (APFs) employed for harmonic and reactive power compensation of nonlinear loads. Two configurations of active shunt APF are presented using time domain analysis for compensation of three-wire (three-phase) and four-wire (three-phase with neutral) systems. For the sake of generality and simplicity, PI (Proportional-Integral) controllers have been proposed for the control of APF. The usefulness of the simulation approach to APF application is demonstrated and discussed in detail. The developed computer package is expected to be a powerful tool to give a better insight to the APF designers.

A hierarchical hybrid system model and its simulation

Abstract: This paper presents a hierarchical hybrid system modeling and simulation framework using the Ptolemy II environment. Ptolemy II is a system-level design tool that supports the integration of multiple models of computation. The modeling of hierarchical hybrid systems is achieved by combining continuous-time models with finite state automata. Breakpoint handling, event detection and invariant monitoring techniques are studied. A hybrid helicopter control system is simulated as an example.

Tips for successful practice of simulation

Abstract: Succeeding with a technology as powerful as simulation involves much more than the technical aspects you may have been trained in. The parts of a simulation study that are outside the realm of modeling and analysis can make or break the project. This paper explores the most common pitfalls in performing simulation studies and identifies approaches for avoiding these problems.

Modeling and simulation methods for plasma processing

Abstract: Methods used for the modeling and numerical simulation of the plasma processes used in semiconductor integrated-circuit fabrication are reviewed. In the first part of the paper, we review continuum and kinetic methods. A model based on the drift-diffusion equations is presented as an example of a continuum model; the model and associated numerical solutions are discussed. The most widely used simulation method for kinetic modeling is the Particle-ln-Cell/Monte-Carlo-Collision (PIC/MCC) method, in which the plasma is modeled by a system of charged superparticles (each of which represents a collection of a large number of ions or electrons) that move in self-consistent electromagnetic fields and collide via given collision cross sections. In the second part of the paper, we review the modeling and simulation of the evolution of surface topography in plasma etching and deposition.

Migration of HLA into Civil Domains: Solutions and Prototypes for Transportation Applications

Abstract: The United States Department of Defense's (DoD) High Level Architecture for Modeling and Simulation (HLA) is a mandatory stan dard for military simulations. The situation in the civil simulation co...

Teachers' Forum: Spreadsheet Modeling and Simulation Improves Understanding of Queues

Abstract: Process-driven spreadsheet queuing simulation is a better vehicle for understanding queue behavior than queuing theory or dedicated simulation software. Spreadsheet queuing simulation has many pedagogical benefits in a business school end-user modeling course, including developing students intuition, giving them experience with active modeling skills, and providing access to tools. Spreadsheet queuing simulations are surprisingly easy to program, even for queues with balking and reneging. The ease of prototyping in spreadsheets invites thoughtless design, so careful spreadsheet programming practice is important. Spreadsheet queuing simulation is inferior to dedicated simulation software for analyzing queues but is more likely to be available to managers and students.

The influence of electromagnetic environment on operation of active array antennas: analysis and simulation techniques

Abstract: This paper presents an overview of active array antennas, system-level nonlinear effects in such antennas, and their modeling and simulation techniques. Advantages of active array antennas, in comparison with passive array antennas, are discussed. The influence of nonlinear distortions and interference in active antennas on the overall system performance is considered. Modeling and simulation techniques that can be applied to active array antennas are substantially different from those used for circuits and systems. Analytical and numerical techniques are used for the analysis of active antennas, with the prevailing use of numerical techniques at the present time. Electromagnetic-level and circuit-level simulation techniques are discussed. System-level simulation techniques are considered in detail, with special emphasis on their application to active array antennas. The "instantaneous" quadrature technique is proposed as an effective tool for numerical simulation of active arrays over wide frequency and dynamic ranges in a computationally-effective way.

Self-consistent simulation of quantization effects and tunneling current in ultra-thin gate oxide MOS devices

Abstract: In this paper we report on the self-consistent modeling and simulation of quantization effects and tunneling current in MOS devices. The simulation model features an original scheme for the self-consistent solution of Poisson and Schrodinger equations and it is used for the extraction of the oxide thickness, by fitting CV curves, and the calculation of the tunneling current. Simulations and experiments are compared for different device types and oxide thicknesses (1.5-6.5 nm) showing good agreement and pointing out the importance of quantum mechanical modeling and the presence of many tunneling mechanisms in ultra-thin oxide MOS devices.

Modeling and transient simulation of planes in electronic packages for GHz systems

Abstract: This paper presents a modeling and simulation approach for ground/power planes in high speed packages. The electrical characteristics of a plane structure are derived in terms of an impedance (Z) or scattering (S) matrix at port locations in the frequency domain by solving Maxwell's equations. Since the solution is a closed form equation, the frequency and transient response can be computed efficiently, requiring small computing time. The response of the plane structure has been captured using rational functions. These functions, which are SPICE-compatible, enable the connection of plane models to the rest of the package for simulation. The frequency and transient response computed using the analytical expression and rational functions have been compared against measurements. The simulation results show good correlation with measured data.

Modeling and simulation of electric drive systems using Matlab/Simulink environments

Abstract: This paper describes a complete modeling and simulation realization on a closed loop induction servomotor drive based on the Matlab/Simulink environment. A simple modeling approach for different types of inverters, based on the dynamic node technique is proposed and a servomotor drive library is described. Based on this library, a speed sensor and/or speed sensorless vector control strategy can be implemented and tested.

ROAMS : Rover Analysis, Modeling and Simulation

Abstract: In this paper, we present the development of ROAMS system for real-time simulation of mobile robotic vehicles. The purpose for the simulation is to provide a virtual testing ground for various subsystems and components of the robotic vehicle, which includes a mechanical subsystem, an electrical subsystem, internal and external sensors, and on-board control software. Using the DARTSIDSHELL framework, the realtime simulator can be applied to both operator-inthe-loop and off-line simulation. This flexibility permits ROAMS to be utilized for various rover tasks in planetary exploration missions, including those of system engineering, scientific research, and operation teams. However, to achieve real-time in the simulation of complex physical systems is non-trivial. Efforts have been made to build the rover model for an efficient and stable simulator. Currently, the rover model is comprised of its mechanical, electrical, and sensor subsystems, all connected with the on-board software. With additional terrain and rock models, we developed a novel solution technique that leads to real-time simulation of the rover traversing Mars-like terrain.

Modular dynamic virtual-reality modeling of robotic systems

Abstract: This article presents the results of research into the field of dynamic simulation of mechanical and robotic systems. The main goal of the whole project is to achieve an efficient modular approach to modeling, in order to make the modeling process easier, ensure its traceability and inspectability, and support model reuse. This is achieved through the declarative definition of models, the standardization of model interfaces, and the object-oriented approach to model development and model data management. The article presents the specific features ofa general-purpose simulation environment, including an overview of the 3D solid modeling software interfaces. The modeling and simulation of a 3-DOF gripper designed for Space robotics applications is also discussed to show the performance of the whole simulation environment in terms of complexity management, efficiency, and accuracy.

On the hla-based coupling of simulation tools

Abstract: The recent development of the High Level Architecture for Modeling and Simulation (HLA) has stimulated interest in the use of distributed, interoperable simulation models. This paper deals with the application of HLA-based coupling of simulation tools. Concepts for the extension of simulation tools with HLA capabilities are outlined and their realization is discussed. Some prototypic federations of commercial simulations tools are discussed.

A Java Implementation of an Environment for Hybrid Modeling and Simulation of Physical Systems

Abstract: Bond graphs are a powerful formalism for modeling the continuous dynamics of physical systems. To model fast continuous changes as discontinuities, hybrid bond graphs introduce an ideal switching element, the controlledjunction, that may inhibit power transfer by enforcing its common variable to be zero. When bond graph storage components become dependent upon one another because of a discrete state change, their stored value may change discontinuously. Consistent values are computed by conserving the physical state variable (e.g., momentum, mass). One discrete state change may cause a number of further discrete state changes without affecting the state vector. When no further changes occur, the state vector is updated and this again may cause a new sequence of discrete state changes. These consecutive discrete state changes can be classified based on parameter abstraction and time scaleabstraction. HYBRSIM implements the hybrid bond graph modeling paradigm as a Java based modeling and simulation environment.

Alpha-SER modeling and simulation for sub-0.25 /spl mu/m CMOS technology

Abstract: Soft errors (single event upset) due to alpha particles from radioactive impurities in packaging materials were first observed on DRAMs. While terrestrial cosmic rays also cause soft errors and dominate logic circuit soft-error rate (SER), alpha-SER contributes significantly to SRAM circuit total SER and increases at a higher rate as processing technology advances to sub-0.25 /spl mu/m feature sizes where even logic nodes become susceptible to alpha strikes. In sub-0.25 /spl mu/m CMOS and beyond, with continuous reduction in supply voltage, decrease in node capacitance, and increase in chip size and transistor count, alpha-SER has become a major reliability concern for logic products. As complex logic products such as microprocessors have numerous circuit types and sizes, accurate and efficient prediction of product SER by comprehending both microscopic charge collection physics and circuit response is both critical and a challenging task. This paper presents a comprehensive modeling and simulation approach, including: (1) circuit critical charge (Qcrit) simulation methodology, (2) compact model for alpha strike charge generation and collection, and (3) statistical algorithms for FIT (failure-in-time) rate simulation. We also present compact model calibration methods and validation using Lawrence Livermore National Lab alpha beams as well as experimentally measured FIT rates of SRAMs in three technology generations. This paper reports the alpha-SER saturation effect, which is extremely critical for future technology planning. Moreover, many of the concepts and models discussed here can be extended to neutron-SER prediction.

Continuous flow models: modeling, simulation and continuity properties

Abstract: The paper presents a generic modeling tool for networks of continuous flow models (CFMs). The elemental building block, called the basic CFM, can be used in the modeling, simulation and sample path analysis of a large class of flow networks. Under certain conditions it constitutes a discrete event dynamic system (DEDS); for simulation thereof there exists a Lindley-like equation. Following the presentation of the basic CFM as a general modeling device, the paper discusses some continuity properties of the attendant flow processes, and points out the possible unbiasedness of LPA for various performance measures.

On-line data processing in simulation models: new approaches and possibilities through HLA

Abstract: The United States Department of Defense's High Level Architecture for Modeling and Simulation (HLA) provides a standardized interface for distributed simulations. The recent advent of HLA has greatly increased interest in the use of distributed, interoperable simulation model components. This paper focuses on how on-line data (i.e. data from real-time dependent processes) can be used in analytical simulation models and how the use of HLA based components can facilitate the integration of this kind of data into simulations. The paper also discusses the issue of cloning federates and federations and introduces some potential applications of cloning for a public transportation prototype example.