Showing papers on "Modeling and simulation published in 1992"

Simulation of Communication Systems

Abstract: Simulation plays an important role in the design, analysis, and implementation of communication systems During the design of complex communication systems it is often infeasible to conduct performance analysis and design tradeoff studies using closed-form mathematical formula techniques Quite frequently, simulation is the only tool available for addressing important issues in the design, analysis, and implementation of communication systems Simulation can be used to verify the functionality of communication systems, evaluate the performance of proposed systems, and generate specifications to guide their design Since the early 1980s a variety of modeling and simulation techniques and tools have been developed and used to support the design and implementation of a broad range of communication systems and products ranging from multi-million-dollar communication satellites to handsets for the next generation of personal communication systems This article presents an overview of the fundamental principles behind modeling and simulation of communication systems Keywords: communication systems; discrete time representation; signals; systems; modeling of functional blocks; simulation of functional blocks; Monte Carlo simulation; random-number generation; performance estimation

Channel modeling and simulation in satellite mobile communication systems

Abstract: An analog model describing signal amplitude and phase variations on shadowed satellite mobile channels is proposed. A linear combination of log-normal, Rayleigh, and Rice models is used to describe signal variations over an area with constant environment attributes while an M-state Markov chain is applied to represent environment parameter variations. Channel parameters are evaluated from the experimental data and utilized to verify a simulation model. Results, presented in the form of signal waveforms, probability density functions, fade durations, and average bit and block error rates, show close agreement with measurements. >

Modeling of integrated manufacturing systems using an object-oriented approach

Abstract: Traditional approaches to the modeling of complex manufacturing systems are expensive, time consuming, and of limited value. Recent developments in several areas (i.e., knowledge engineering, software engineering, modeling formalisms, engineering workstations, and database systems) are now to the point that a meaningful convergence can be crafted to yield a modeling environment far superior to any we have known in the past. Fundamental to this new approach to modeling are the recent developments in object-oriented programming and related technologies. A research team at Oklahoma State University has been exploring alternative approaches to the modeling and simulation of complex manufacturing systems since 1985. This paper argues for a fundamental paradigm shift in the development and utilization of models within a CEM framework.

Constitutive modeling and simulation of energy absorbing polyurethane foam under impact loading

Abstract: The compressive-stress strain response of polyurethane foam under uniaxial compressive impact loading has been studied. The development of a uniaxial constitutive model from strain rate controlled compression tests is detailed. Density and temperature functions have been added to the integral power model proposed by Schwaber, Meincke, and Nagy. The model assumes that the effects of density, temperature, strain and strain rate on stress are separable functions. The model correlated well with actual static compression tests and was used successfully to predict the impact response of energy absorbing polyurethane foam under uniaxial compressive loading.

Reasoning about energy in qualitative simulation

Abstract: Qualitative modeling and simulation make it feasible to predict the possible behavior of a mechanism consistent with an incomplete state of knowledge. Though qualitative simulation predicts all possible types of behavior of a system, it can also produce spurious behavior, i.e., behavior that corresponds to no solution of any ordinary differential equation consistent with the qualitative model. A method for reasoning about energy that eliminates an important source of spurious behavior is presented. This method is applied to a nonlinear proportional-integral controller, and it is shown that qualitative simulation captures the main qualitative properties of such a system, such as stability and zero-offset control. It is believed that this is a significant step toward the application of qualitative simulation to model-based monitoring, diagnosis, and design of realistic mechanisms. >

More accurate modeling of gas insulated substation components in digital simulations of very fast electromagnetic transients

Abstract: It is pointed out that very fast electromagnetic transients caused by switching operations in gas insulated substations (GIS) cannot be calculated if conventional techniques of modeling and simulation are used. The selection and adjustment of the most suitable models as well as determinations of their limitations in digital simulations of very fast transients in GIS are investigated. Results obtained from very extensive field tests and from digital simulations for different types of GIS have been used for the development of more accurate models for GIS components and GIS as a whole. A comparison between field test and calculation results permits the development of a model which takes into account the most decisive physical phenomena inherent in the very fast transients in the GIS. This is a prerequisite for designing and manufacturing power system components as well as for control and protection of the system. >

Biomedical Modeling and Simulation on a PC

Abstract: Why use computer simulation as an educational tool? Why is computer simulation based on mathematical models? What kinds of computer simulations are there? What is the difference between computer simulation and modeling? What is the difference between a model and a program? What are some advantages and disadvantages of computer simulation programs? What is the difference between learning through discovery and various kinds of coached learning? In which five ways can computer simulation programs be used? 2.1 Computer Simulation and Modeling

A summary of ring rolling technology—II. Recent trends in process modeling, simulation, planning, and control

Abstract: A summary of the ring rolling research in process planning, modeling, simulation and control is presented. In this technology survey, recent trends in the application of computers in process planning and control, and research in process modeling and simulation are emphasized. Current research at the Engineering Research Center for Net Shape Manufacturing aimed at reducing defects in rolled rings and increasing the productivity of ring mills via modeling and simulation of the ring rolling process is also briefly included.

Design and implementation of a highly reusable modeling and simulation framework for discrete part manufacturing systems

Abstract: This paper describes ongoing research in the area of “Advanced Modeling Methodologies for Simulation of Complex Discrete Part Manufacturing Systems” in the Center for Computer Integrated Manufacturing at Oklahoma State University. We focus on presenting the design and implementation details of a modeling and simulation environment under development. First, we briefly describe the concept of model reusability and then show how the concept of separation of physical, information, and control elements of a model can lead to model reusability. Next, we outline the structure of our modeling and simulation environment and discuss the implementation of this structure in Smalltalk-80. model such as changes in the structure of the system and their impact on the system performance cannot be easily handled. Thus, the traditional languages facilitate model reusability only to a limited degree. In this paper, we present an implementation of a highly reusable modeling and simulation framework for discrete part manufacturing systems. In Section 2, we present some background information. In Section 3, we discuss some fundamental issues for incorporating reusability in a simulation framework. Section 4 extends the reusability concepts as applied to our modeling and simulation framework for discrete part manufacturing systems. The next section deals with the design and implementation issues of the modeling and simulation environment. Section 6 presents an illustrative example

Modeling, Simulation And Optimization Of Analog Macromodels

Abstract: In this paper, we present a set of nnnlog nincroinodel development and siniulation tools which enables circuit designers t o overconie some of ihe typ icn l bottlenecks in ihis approach t o simzilalion. The m u i n focus i s on ih e m a crorii od eling in e 2 A od olog y a n d 1 w o 11, e U p rog ra ins called iMacGen and iMacClik. A l o w p a s s filler is iiscd t o illuslrule the iiiacroiiiodeling process.

Modeling and simulation of networks using CSIM

Abstract: In performance analysis of communication networks, simulation modeling is often used because it provides a convenient and reliable tool for such studies. In this paper, the authors present the use of a discrete-event simulation language- CSIM-to model the local networks by providing various simulation case studies. A description of CSIM is provided along with fragments of the code for simulating several token ring network models, as examples.

Modeling and simulation of the resource allocation process in a bandwidth-on-demand satellite communications network

Abstract: The authors describe the modeling and simulation of a frequency-division multiple-access (FDMA) satellite bandwidth-on-demand (BOD) service. The class of resource allocation processes to which the satellite BOD application belongs is identified and contrasted with more common resource allocation processes. Several unique features of BOD service complicate the performance specification, modeling, and analysis. The authors divide the modeling problem into three fundamental components: modeling the resource algorithm and modeling the processing of individual resource requests. These modeling components are illustrated with the satellite BOD application. In addition, simulation of the resource allocation requires three additional components: an easy-to-use user input interface, performance measures and statistics gathering, and presentation of simulation results (user output interface). The architecture of the simulation software (resource allocation analysis program, or RAAP) is presented in terms of these six components. To illustrate RAAP's capabilities, example simulation results are given. >

Modelling of power systems in Omola for transient stability studies

Abstract: It is illustrated how the universal, equation-based, and object-oriented modeling language Omola facilitates modeling and simulation. The application is modeling of power systems for transient stability studies. However, the intention is not to develop a full-fledged power system mode, but to illustrate general ideas with concrete examples. The focus is on structural issues of model decomposition, which give flexibility. Model component shells with well-defined terminals which can be easily used to define models of different complexity through inheritance are developed. These model components have been used to implement a 16-machine power system model of the Scandinavian power grid. Simulations agree very well with results obtained from ABB's package Simpow. >

Modeling and simulation of a high-performance PACS based on a shared file system architecture

Abstract: Siemens and Loral Western Development Labs have designed a Picture Archiving and Communication System capable of supporting a large, fully digital hospital. Its functions include the management, storage and retrieval of medical images. The system may be modeled as a heterogeneous network of processing elements, transfer devices and storage units. Several discrete event simulation models have been designed to investigate different levels of the design. These models include the System Model, focusing on the flow of image traffic throughout the system, the Workstation Models, focusing on the internal processing in the different types of workstations, and the Communication Network Model, focusing on the control communication and host computer processing. The first two of these models are addressed here, with reference being made to a separate paper regarding the Communication Network Model. This paper describes some of the issues addressed with the models, the modeling techniques used and the performance results from the simulations. Important parameters of interest include: time to retrieve images from different possible storage locations and the utilization levels of the transfer devices and other key hardware components. To understand system performance under fully loaded conditions, the proposed system for the Madigan Army Medical Center was modeled in detail, as part of the Medical Diagnostic Imaging Support System (MDIS) proposal.

Study of modeling and simulation for a chemical production system

Abstract: The purpose of this paper is to demonstrate the advantages that may be obtained through the use of simulatian tools in the design of a production workshop and more specifically, in validating a structure for production and a logic for control in the field of chemical processes. Such simulation concerns a type of production which is totally different from manufacturing type, as the former are continuous processes that can be rendered discrete. After a rapid presentation of the various theoretical approaches to modeling and simulation tools that may be used in this field, we will describe the system to be designed and its characteristics. Then we will go on to the approach to modeling we have retained and the simulation carried out in order to study the system dynamically. Finally, we will present the results we reached and we will draw some conclusions on the advantages and the limits of the study made.This study, which aims at designing and evaluating the performances of a production unit in an internatio...

Multibody dynamics software for controlled vehicle simulation

Abstract: The method of multibody systems achieved major importance in vehicle dynamics for traditional and advanced applications In the context of concurrent engineering and advanced vehicle design, multibody formalisms represent the core of every software package for modeling and simulation The paper presents a multibody system datamodel and the database RSYST linking software models In detail the moduls NEWEUL for the symbolical generation of motion and NEWSIM for the simulation are considered As an example the multibody dynamics software is applied to a van with actively controlled suspensions

Modeling a highly reliable fault-tolerant guidance, navigation, and control system for long duration manned spacecraft

Abstract: The use of a reliability modeling simulation tool to evaluate the reliability of a hypercube multiprocessor which is a candidate architecture for guidance, navigation, and control systems for long-duration manned spacecraft is described. The simulation tool was used to evaluate homogeneous Markovian, nonhomogeneous Markovian, and non-Markovian models of the hypercube. The study focuses on the effect of assuming Weibull decreasing component failure rates compared to the usual assumption of constant component failure rates. The effect of the use of cold spares on system reliability under the assumption of both constant and Weibull decreasing failure rates is also examined. The authors discuss simulation applied to discrete-state reliability models and the role that importance sampling can play. The results obtained from the models under the differing assumptions about failure rate behavior are presented. >

Modeling and Simulation for Automated Yacht Design

Abstract: Computational simulation is an important tool for predicting the behavior of physical systems. Many powerful simulation programs exist today. However, using these programs to reliably analyze a physical situation requires considerable human effort and expertise to set up a simulation, determine whether the output makes sense, and repeatedly run the simulation with different inputs until a satisfactory result is achieved. Automating this process is not only of considerable practical importance but also raises significant AI research issues in the areas of spatial reasoning and modeling of physics and numerical methods. The application domain described in this paper is the design of racing yachts.

Computer modeling and simulation of vehicle dynamics

Abstract: Computer simulation combines the two approaches that scientists and engineers have for determining how physical systems behave: experimental and analytical. An engineer can run tests on the computer, using the same basic investigative methodology that would be used with tests of the physical system. This article reviews the development and use of simulation tools over the time of UMTRI's existence, and describes new computerized modeling and simulation technology that has been recently developed at UMTRI. The core of the technology is a modeling language called AUTOSIM, now distributed commercially. One of the first applications has been the development of a user-friendly simulation software package for trucks and tractor-trailer vehicles, called TruckSim.

Distributed Communication Network Systems Performance Modeling

Abstract: This paper will describe the use of system performance modeling and simulation in designing large, complex distributed communication network systems. These systems include both local and wide area configurations, utilizing a variety of protocols, hardware, communication media, etc. This paper will show how Harris was able to apply the information obtained from the modeling activity to understand the behavior of the systems being architected and to verify that specific system performance requirements are met.

An object-oriented approach to computer architecture simulation

Abstract: An object-oriented approach to modeling and simulation computer architectures is presented. Rather than concentrating on a specific system, the more generic concepts of processors, memories, clocks, registers, instruction sets, etc. are developed. By building upon these basic concepts, it is then possible to simulate virtually any processor to nearly any level of detail. >

Modeling And Simulation Of aSigma;aDelta; A/D Converters Using A Mixed-mode Simulator

Abstract: With the development of a set of building blocks for SampledData System modeling, a mixed-mode system consisting of continuous analog, sampled analog value and digital state blocks can be simulated. A triple-stage MASH A/D converter using these building blocks has been described to illustrate the procedure and advantages of this approach.

Modeling and simulation of a six-legged walking robot power system

Abstract: Reliable models and simulation enhance design and optimization capabilities considerably for complex systems. This study is concerned with such issues for a six-legged rough terrain walking vehicle power system that includes the associated control systems. The power system of the vehicle can be divided into three broad categories: leg systems, mechanical transmission system, and the primary power source and energy storage system. Modeling techniques, detailed analytical models, and a comprehensive nonlinear digital simulation are developed for precise performance predictions, interaction studies, parametric studies, and to aid in the mechanical and control design process. Validation of the models is provided by several experiments performed on a prototype leg and the vehicle. The models and simulatian predictions have resulted in a significant improvement in vehicle performance.

Structuring Biological Systems: A Computer Modeling Approach

Abstract: Structure of Genetic Algorithms in Biological Systems (S.S. Iyengar, L. Prasad, and D. Morton). Computer Modeling and Artificial Intelligence: An Introductory Review (D.P.F. Moller). Modeling of Biological Systems at the Molecular Level: Electronic and Molecular Properties of Complex Molecular Systems (N.R. Kestner). A Mathematical Model of Renal Hemodynamics and Excretory Function (T.G. Coleman and J.E. Hall). Cognitive Aspects in the Modeling and Simulation of Complex Biological Systems (B.P. Bergeron and R.L. Rouse). Entropy-Based Probability Distributions for Modeling of Environmental and Biological Systems (V.P. Singh). Computer Simulation in Cancer Research (W. Duchting). Appendices. Index.

An integrated approach for electrical performance analysis of multichip modules

Abstract: The authors describe an integrated approach to evaluate the electrical performance of multichip modules. A software system consisting of modeling and simulation tools to extract geometry from a placement and routing system, compute electrical parasiticsm, and create equivalent circuit files to perform circuit simulations has been developed. This tool was used in designing an i486 microprocessor-based multichip module. Typical results from the analysis are presented. >