Showing papers on "Modeling and simulation published in 1988"

Modeling and simulation of spacecraft power systems

Abstract: Modeling of a complete spacecraft power processing system is presented, using the Boeing EASYS software. Component models are developed, and several system models including a solar array switching system, a partially shunted solar system, and cosmic background explorer (COBE) system are simulated. The modes of operation of the power system, such as shunt mode, battery-charge mode, and battery-discharge mode, are simulated for a complete orbit cycle. >

Dynamic Models and Discrete Event Simulation

Abstract: 1. Systems and Models 2. Deterministic Models 3. Stochastic Models 4. Identification of Stochastic Systems 5. Modeling of Complex Systems 6. The Experimental Aspect of Simulation 7. The Modeling Aspect of Simulation 8. The Programming Aspect of Simulation 9. Future Trends in Modeling and Simulation 10. Simulation Examples

Transient simulation of integrated AC/DC systems. I. Converter modeling and simulation

Abstract: A general and efficient method is presented for transient simulation of HVDC converters. The method utilizes a novel algorithm that is based on network topological concepts and provides an efficient solution to the problem of modeling the inherently nonlinear characteristics and time-varying topology of static power converters caused by the switching action of the thyristor valves. The application of the algorithm to a six-pulse converter unit results in an extremely flexible and efficient model that can be easily interfaced to both the AC and DC sides of an integrated AC/DC system. >

Accurate modeling and simulation of parallel interconnection in high-speed integrated circuits

Abstract: The evaluation of the time-domain performance of interconnection lines is becoming increasingly more important in the analysis and design of high-speed integrated circuits. An accurate computer model for n coupled microstrip lines is developed for circuit simulation. Modal analysis is applied to decouple the n coupled line system into n independent lines and the characteristic solution of the lossy transmission line equation is modeled into a simple time-varying equivalent circuit. This model has been implemented into a circuit simulator, called iSMILE, that significantly reduces the model development time. Simulation results on propagation delay times and crosstalks are presented for the case of high-speed GaAs HEMT (high-electron-mobility transistor) integrated circuits. >

Cognitive skills in modeling and simulation. (volumes i and ii)

Abstract: Major advances in simulation techniques have resulted from refinements to our understanding of the modeling and analysis processes. Previous work has provided the framework for advances in the three major support technologies of (1) algorithms, (2) data structures, and (3) statistical methods. The emergence of theories in knowledge acquisition and reasoning from the domain of Artificial Intelligence (AI) provide new methods for study of the cognitive processes of the customer and the simulation analyst within a decision scenario framework. The availability of software and hardware tools for implementing these theories provide a promising mechanism for the construction of advanced modeling systems based on the results of relevant models and theories related to the cognitive process. This research establishes a base from which an intelligent, model based, systems simulation environment can be constructed. The ultimate goal of such a system is to partially or totally replace the existing human systems simulation analyst. This dissertation will address the underlying theories and strategies of how those cognitive processes can be represented and supported in a knowledge based environment.

Modeling and simulation of a supercharger

Abstract: A dynamic model is developed for simulating and predicting performance for superchargers of relatively arbitrary geometric configuration. A thermodynamic control volume approach and bond graph models are used to derive continuity and energy equations linking the various control volumes. Bond graphs also serve to study and understand the causal implications of laws governing flows between control volumes and system dynamics. Heat transfer is neglected. Simulation outputs include time histories of pressure, temperature, mass, and energy associated with each control volume, time histories of the various flows in the supercharger, and overall volumetric efficiency. Volumetric efficiencies are predicted over a wide range of speed/pressure ratio combinations and are within three percent of experimentally measured values. The simulation is used to investigate the sensitivity of supercharger performance to several key design parameters, including rotor-rotor separation, and rotor-housing and side plate clearance distances.

Modeling and simulation of an analog charge-pump phase locked loop

Abstract: We describe a nonlinear computer simulation model of an Ana log Charge-Pump Phase Locked Loop (ACP-PLL). Offsets of the Phase Detector and Analog Charge-Pump are modeled as dis turbances to simulat...

Modeling and simulation of coupled lossy lines for VLSI interconnections

Abstract: The authors present techniques for the analysis of signal propagation in the interconnections used in VLSI systems. The propagation is modelled by coupled transmission lines which include losses. For conductors whose thickness is small compared to the skin depth over the principal spectrum of the pulse being propagated, the losses can be treated as frequency-independent; otherwise, the losses must be calculated as a function of frequency. It was observed that the inductance may be approximately treated as constant, but the resistance variations in frequency may be significant. A semi-analytical method for computing the transients in lossy lines serves as the basis for the simulation of nonuniform lines. >

Modeling and Simulation in Medicine: The State of the Art

Abstract: Computer modeling and simulation techniques are playing an increasingly central role in changing both the way medicine is taught and the way it is practiced. Fundamental to the art and science of modeling and simulation is an underlying assumption that insight into system behavior can be developed or enhanced from a model that adequately represents a selected subset of the system's attributes. Simulation design considerations include: the provision of an appropriate user interface; determining optimal simulation complexity; defining a tutorial strategy; selecting authoring tools; assessing hardware requirements; identifying user needs; defining pedagogical goals; verification and validation; and system evaluation. Significant trends in simulation include the development of improved authoring tools, migration to desktop hardware platforms, and integration of simulation techniques with other types of applications.

Solar Cell Modeling and Simulation

Abstract: : An important aspect of solar cell design and analysis is the ability to model the wide variety of structures which are presently under study. This document reports on the application of the Poisson and Continuity Solver (PISCES) semiconductor modeling code to solar cell studies. The original program supplied by Stanford University has been modified to include optical generation processes as required and to correct a number of significant programming errors. In its present form, nearly all solar cell structures which have been proposed can be simulated by PISCES, as well as a variety of other opto-electronic devices and processes. The material parameters which may be adjusted include, but are not restricted to, doping profiles, bulk, interface and surface recombination characteristics, and contact properties such as ohmic, Schottky or insulating. The major model selections available include Boltzmann or Fermi- Dirac carrier statistics, voltage or current boundary conditions, and steady state or time-dependent analyses. The program capabilities are demonstrated by analysis of several state-of-the art solar cell designs in which the important design parameters are varied and their effect on the cell output parameters shown.

Ada simulation technology - methods and metrics

Abstract: This paper describes the impact of the Ada programming language on the development and use of simulation models. Based upon the development in Ada of a discrete-event simulation package (A*SIM), Ada is shown to provide numerous language features and methodologies that are ideally suited for modeling and simulation. Productivity and performance metrics collected during development and extensive use of A*SIM are also presented to provide quantitative comparisons of Ada-based modeling and simulation with previous approaches.

A centralized methodology for multi-level abstraction in simulation

Abstract: Simulation systems need to be able to serve the need of a large domain of users with varying requirements and expectations of a simulation system. The varying degree of requirements by a larger group of users will require the use of multiple abstraction levels within a simulation environment. A methodology for implementing simulation systems with multiple abstraction levels has been developed. This methodology permits the simulation system to have great flexibility in satisfying the requirements of a broad range of users.

A real-time statistical polarimetric target model

Abstract: A statistical approach to modeling and simulation of polarimetric electromagnetic fields backscattered from a reflecting body of a complex shape is described. A statistical scattering matrix is formulated and estimated for Rayleigh and Rician fluctuating (reciprocal and nonreciprocal) targets. The backscattered and received fields are modeled as a stochastic processes for arbitrary combination of transmit and receive polarization. A Monte Carlo simulation of a tank target is performed to verify the assumptions and approximations made and to demonstrate the feasibility of the real-time model. The results presented can be generalized to polarimetric clutter and to decoy modeling and simulation. >

Modeling of jet vane heat-transfer characteristics and simulation of thermal response

Abstract: : The development of a dynamic computational model capable of predicting, with the requisite design certainty, the transient thermal response of jet vane thrust control systems has been undertaken. The modeling and simulation procedures utilized are based on the concept that the thermal processes associated with jet vane operation can be put into a transfer function form commonly found in the discipline of automatic controls. Well established system identification methods are employed to formulate and verify the relationships between the various gains and frequencies of the transfer function model and experimental data. Keywords: Dynamic systems modeling; Modeling; Model simulation; Thermal response; Parametric system identification; Theses.

Ada™ simulation technology- methods and metrics

Abstract: This paper describes the impact of the Ada programming lan guage on the development and use of simulation models. Based upon the development in Ada of a discrete-event simulation package (A*SIM), Ada is shown to provide numerous language features and methodologies that are ideally suited for modeling and simulation. Productivity and performance metrics collected during development and extensive use of A*SIM are also pre sented to provide quantitative comparisons of Ada-based model ing and simulation with previous approaches.

Modeling and simulation of power conditioning equipment containing saturable inductors using a personal computer

Abstract: The authors present a technique for the simulation of power-conditioning equipment containing saturable inductors. An ideal sampler, variable gain, and clamp are used to model the saturable inductor. A state variable is assigned to this group of elements. A linear homogeneous state model is formulated and solved using the state-transition-matrix approach. The state variable associated with the sampler, gain, and clamp are held constant for the solution of the state model. These added states are updated using a jump matrix and nonlinear description function. The solution achieved using the technique compares favorably with the solution obtained from a simulation using the Electromagnetic Transients Program. >

Modeling and simulation of 1553 bus for upset tolerance experiments

Abstract: Since satellite systems are particularly susceptible to transient faults induced by the radiation environment, a satellite communication protocol model has been developed for experimental research purposes. The model implements the MIL-STD-1553B protocol, which dictates the modes of communication between several satellite subsystems. The model has been developed using the behavioral and structural capabilities of the HILO simulation system. Perturbations in the control flow of the system due to transient faults can be studied by injecting faults in the model. The time and location of these faults are chosen pseudorandomly. Error-detection capabilities are incorporated by two different techniques: one consists of inserting error-checking tags in existing system software and the other uses the concept of path signature analysis. On the basis of the results of these experiments, effective error recovery techniques will be developed. >

Computer-based modeling, simulation and analysis in power electronic control systems

Abstract: Computer-aided methods in analysis and design of power electronic control systems are discussed. The problems and difficulties concerned with analysis and design peculiar to power electronic control systems are reviewed. Promising simulation and sensitivity analysis methods are described and the related design problems are discussed. The proposed methods are general enough to handle almost all existing power electronic control systems and easy to implement into program packages. >

Modeling and simulation of robot arms with flexible links

Abstract: Title of Thesis: Modeling and Simulation of Robot Arms with Flexible Links John G. Danis, Master of Science, 1988 Thesis directed by: Dr. Frederick D. Chichester F.D.C. The design of lightweight robot arms introduces a degree of flexiblity in the individual links which renders the arm difficult to control. Solution of the control problem requires accurate and detailed mathematical models of the arm dynamics. A comprehensive survey of the current literature in this area has shown that although many such models exist, there is a great diversity in their structure, function, and applicability. The different objectives and techniques of model development which lead to this diversity are examined and summarized in this thesis. Bases for classification of the mathematical models and techniques of development are established, and a general development methodology is proposed for each class of model. Computer simulations of relevant portions of the model development are used to support these general development methodologies. The model development and classification processes are demonstrated by their application to several current models. MODELING AND SIMULATION OF ROBOT ARMS WITH FLEXIBLE LINKS