Electrical and Computer Engineering Commons^™

Gyroless Line-Of-Sight Stabilization For Pointing And Tracking Systems, Marcelo C. Aigrain

Department of Electrical and Computer Engineering: Faculty Publications

A new platform stabilization approach is described where miature, low-cost, linear accelerometers are used (instead of gyroscopes) for line-of-sight (LOS) stabilization. This is accomplished by placing the accelerometers at strategic locations and combining their outputs so that angular motion is determined from linear acceleration measurements. The control system uses the sensed angular accelerations to generate movement commands for the gimbal servomotors in the stabilization platform. This counterrotates the imaging device to stabilize its LOS. The use of accelerometers allows the servo system to operate in an acceleration control mode, which is more desirable than position or velocity control modes, typical …

Electronic Simulation Of The Temporal Characteristics Of Photon Memory Echoes And Some Related Applications, Yuwen Kuo, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

The characteristics of nonlinear photon memory echoes are investigated by means of SPICE simulations using equivalent resonator ensembles. By developing implicit nonlinear circuit models in the memory echo domain, the triple product formalism of electronic holography, involving correlation and convolution, is tested for the storage and recall of arbitrary signals and/or data bit streams in both time-inverted and nontime-inverted modes. Furthermore, a few specific optical data processing applications are also simulated in which the mixed binary multiplication of two or more binary bit streams is achieved.

Higher order products, optical pattern recognition, and other possible applications are also discussed. It …

Variable Structure End Point Control Of A Flexible Manipulator, Shailaja Chenumalla, Sahjendra N. Singh

Electrical & Computer Engineering Faculty Research

We treat the question of control and stabilization of the elastic multibody system developed in the Phillips Laboratory, Edwards Air Force Base, California. The controlled output is judiciously chosen such that the zero dynamics are stable or almost stable. A variable structure control (VSC) law is derived for the end point trajectory control. Although, the VSC law accomplishes precise end point tracking, elastic modes are excited during the maneuver of the arm. A Linear stabilizer is designed for the final capture of the terminal state.

The Application Of Neural Networks To Optimal Robot Trajectory Planning, Daniel J. Simon

Electrical and Computer Engineering Faculty Publications

Interpolation of minimum jerk robot joint trajectories through an arbitrary number of knots is realized using a hardwired neural network. Minimum jerk joint trajectories are desirable for their similarity to human joint movements and their amenability to accurate tracking. The resultant trajectories are numerical rather than analytic functions of time. This application formulates the interpolation problem as a constrained quadratic minimization problem over a continuous joint angle domain and a discrete time domain. Time is discretized according to the robot controller rate. The neuron outputs define the joint angles (one neuron for each discrete value of time) and the Lagrange …

Suboptimal Robot Joint Interpolation Within User-Specified Knot Tolerances, Daniel J. Simon, Can Isik

Electrical and Computer Engineering Faculty Publications

Approximation of a desired robot path can be accomplished by interpolating a curve through a sequence of joint-space knots. A smooth interpolated trajectory can be realized by using trigonometric splines. But, sometimes the joint trajectory is not required to exactly pass through the given knots. The knots may rather be centers of tolerances near which the trajectory is required to pass. In this article, we optimize trigonometric splines through a given set of knots subject to user-specified knot tolerances. The contribution of this article is the straightforward way in which intermediate constraints (i.e., knot angles) are incorporated into the parameter …

Robot Force Velocity Control Using Expert System For Control Mode Changes, William R. Doggett

Electrical & Computer Engineering Theses & Dissertations

The most important property of an automated mechanical system is reliable execution of a specified task. Automated mechanical systems work best in precisely structured environments where all operations are repeatable. Typically, these systems are difficult to modify and expensive to install. Sensors can be used to detect disturbances, thus reducing hardware cost by offsetting the need for precise rigid construction components. Sensors, however, increase the complexity and cost of the control software. Efficient methods of reacting to sensor information during automated system operation are required to reduce software complexity and expense.

This thesis analyzes a robotic construction task and describes …

A Systolic Simulation And Transformation System, Ronald I. Greenberg, H.-C. Oh

Computer Science: Faculty Publications and Other Works

This paper presents a CAD tool, SystSim, to ease the design of systolic systems. Given a high-level, functional description of processors, and a high-level description of their interconnection, SystSim will perform simulations and provide graphical output. SystSim will also perform transformations such as retiming, which eases use of the methodology of Leiserson and Saxe of designing a system with broadcasting and then obtaining a systolic system through retiming.

The Anatomy Of Programming Languages, Alice E. Fischer, Frances S. Grodzinsky

Electrical & Computer Engineering and Computer Science Book Series

The specific goals of this book are to help students learn: *To reason clearly about programming languages. *To develop principles of communication so that we can evaluate the wisdom and utility of the decisions made in the process of language design. *To break down language into its major components, and each component in to small pieces so that we can focus on competing alternatives. *To define a consistent and general set of terms for the components out of which programming languages are built, and the concepts on which they are based. * To use these terms to describe existing languages, …

Design And Implementation Of Fuzzy Logic Controllers. Thesis Final Report, 27 July 1992 - 1 January 1993, Osama A. Abihana, Oscar R. Gonzalez

Electrical & Computer Engineering Faculty Publications

The main objectives of our research are to present a self-contained overview of fuzzy sets and fuzzy logic, develop a methodology for control system design using fuzzy logic controllers, and to design and implement a fuzzy logic controller for a real system. We first present the fundamental concepts of fuzzy sets and fuzzy logic. Fuzzy sets and basic fuzzy operations are defined. In addition, for control systems, it is important to understand the concepts of linguistic values, term sets, fuzzy rule base, inference methods, and defuzzification methods. Second, we introduce a four-step fuzzy logic control system design procedure. The design …

Design And Development Of A High-Speed Winograd Fast Fourier Transform Processor Board, James F. Herron

Theses and Dissertations

Since 1985, the Air Force Institute of Technology has pursued a project to develop a 4080-point Discrete Fourier Transform processor using the Winograd Fourier Transform Algorithm (WFTA) and Good-Thomas Prime Factoring Algorithm (PFA). In the first attempt to build a working system, this research effort designed and constructed, in part, a modified single processor architecture in order to demonstrate the proof of concept of the WFTA system design. This prototype architecture is simpler in implementation but uses the same principles and procedures as those of the 4080-point WFTA design. The design developed in this thesis was validated using the Very …

Satcom General Purpose Modem Dscs Iii Sct Beacon Telemetry Display, James D. Coppola

Theses and Dissertations

This thesis documents the design and implementation of a DSCS III single Channel Transponder (SCT) beacon telemetry display. The system is a personal computer based design which interfaces to three SCT beacon receiver/demodulators. The software was designed to decode and display both the DSCS III A and DSCS HI B satellite beacons. Recordings of the SCT beacon display can be made on paper and/or magnetic media when triggered by the user, a watchdog timer, or the SCT command accept telemetry bit. In addition, the system can be configured with an IRIG B Universal Time Coordinates (UTC) card which enables the …

Computer Simulation Of A General Purpose Satellite Modem, William L. Montgomery Jr.

Theses and Dissertations

The purpose of this research was to model and simulate the performance of a digital phase shift keyed satellite modem. The probability of bit error (P sub b) at different levels of energy per bit to noise power ratio (E sub b/N sub o) was the performance measure. The channel was assumed to contribute only additive white Gaussian noise. A second order Costas loop performs demodulation in the modem and was the key part of the simulation. The Costas loop with second order Butterworth arm filters was tested by finding the response to a phase or frequency step. The Costas …

Interaction Of Profiled Light With Contrapropagating Acoustic Waves: Fourier Transform Approach, Partha P. Banerjee, Chen-Wen Tarn, Jaw-Jueh Liu

Electrical and Computer Engineering Faculty Publications

A straightforward Fourier-transform approach is employed to investigate acousto-optic interaction between an input optical beam with arbitrary profile and contrapropagating cw sound in the Bragg regime. The process can be analyzed in terms of the simultaneous scattering of light by the two sound waves in the interaction region. Analytic expressions for the equivalent transfer functions are obtained and the scattered light profiles are plotted.

Analysis Of Multifrequency Dispersive Optical Bistability And Switching In Nonlinear Ring Cavities With Large Medium-Response Times, Pawel Pliszka, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

Using a simple model of a ring cavity comprising a cubically nonlinear medium, we analyze dispersive optical bistability in the presence of more than one spectral component. We show the phenomenon of so-called competition for resonance. In addition to presenting cavity characteristics for the cases of two and three different frequencies, we also discuss the general method for finding steady-state solutions and checking their stability. A simple and efficient algorithm, based on a relaxation method, is devised to find steady-state solutions satisfying appropriate boundary conditions. The relaxation dynamics is physically related to a finite response time of the medium.

An Application Of Neural Networks In Data Communication Real-Time Resource Reallocation, Qing Fan

Electrical & Computer Engineering Theses & Dissertations

This thesis presents an application of artificial neural networks in real-time resource reallocation, a methodology used in the implementation of an intelligent interface node in the Computer Integrated Manufacturing (CIM) environment. In particular, the problem is formulated using a Hopfield neural network model. The real-time reallocation problem is mapped into a two-dimensional matrix of neurons similar to Hopfield and Tank's approach to the traveling salesman problem (TSP) . An energy function is formulated in terms of the hard constraints and the solution cost. The interconnection weights and the input biases are determined by the energy function. It is shown through …

An Intelligent Database For Psubot, An Autonomous Wheelchair, Dieudonne Mayi

Dissertations and Theses

In the design of autonomous mobile robots, databases have been used mainly to store information on the environment in which the device is to operate. For most of the models and ready systems, the database when used, is not a stand alone component in the system, rather it is only intended to keep static information on the disposition and properties of objects on the map.

In this thesis is implemented an intelligent database. It combines static facts to build more information. An intelligent database such as this one will be a plus for an intended autonomous machine such as the …

Model-Based Target Recognition Using Laser Radar Imagery, Robert Y. Li

Department of Electrical and Computer Engineering: Faculty Publications

Autonomous target recognition can be assisted by using CO2 laser radar data. Of these data, range data provide 3-D geometric information and Doppler data boundaries of moving targets. A powerful 3-D feature extraction algorithm based on the Hough transform is used to obtain the orientations and dimensions of the target. This information is then utilized by an inference procedure that recognizes targets based on the available evidence from the sensory data. The experimental results using actual laser radar imagery are successful and the procedure can be used for the future development of a model-based system for target recognition.

Analysis Of Algorithms For Velocity Estimation From Discrete Position Versus Time Data, Ronald H. Brown, Susan C. Schneider Phd, Michael G. Mulligan

Electrical and Computer Engineering Faculty Research and Publications

Algorithms for constructing velocity approximations from discrete position versus time data are investigated. The study is limited to algorithms suitable to provide velocity information in discrete-time feedback control systems such as microprocessor-based systems with a discrete position encoder. Velocity estimators based on lines per period, reciprocal-time, Taylor series expansion, backward difference expansions, and least-square curve fits are presented. Based on computer simulations, comparisons of relative accuracies of the different algorithms are made. The least-squares velocity estimators filtered the effect of imperfect measurements best, whereas the Taylor series expansions and backward difference equation estimators respond better to velocity transients.

Translation Of 'Kamalakanta: A Collection Of Satirical Essays And Reflections', Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

This venture was born initially out of the desire to make those works of Bengali literature which have moved me profoundly, and which I consider first-rate by any yardstick, available to friends and fellow enthusiasts who cannot read the original. In attempting to channel literary and philosophical masterpieces into a different medium, I Have experienced firsthand the formidable challenge that a translator must face because not only of the barrier imposed by the languages involved, but perhaps more so because .of his or her own severely inadequate faculty being called upon to match both the genius and the inspiration of …

A Prolog System For Converting Vhdl-Based Models To Generalized Extraction System (Ges) Rules, Michael A. Dukes, Frank M. Brown, Joanne E. Degroat

AFIT Documents

With the advent of VHDL accurate documentation of hardware designs is a practical reality. In the past, schematics were typically used for documentation of hardware designs. However, these schematics would usually become obsolete as the hardware design was being constructed. Deviations in the hardware design would sometimes not be reflected in the schematics. For design groups, failure to update schematics could lead to different parts of a hardware design becoming incompatible. A system to ensure compliance of hardware with its VHDL documentation is presented in this paper. The system, vhdl2ges, is meant to help guide the development of hardware by …

Low To Medium Level Image Processing For A Mobile Robot, Cecilia H. Espinosa

Dissertations and Theses

The use of visual perception in autonomous mobile systems was approached with caution by mobile robot developers because of the high computational cost and huge memory requirements of most image processing operations. When used, the image processing is implemented on multiprocessors or complex and expensive systems, thereby requiring the robot to be wired or radio controlled from the computer system base.

Hereby developed is a simple, inexpensive and automatic image processing subsystem that is completely implementable on a PC-386SX with 640K base memory. The subsystem will serve as the front end of the vision system for the PSUBOT, an autonomous …

Hybrid Wafer Scale Microcircuit Integration -- [ 5008213 ], Edward S. Kolesar Jr.

AFIT Patents

A wafer scale integration arrangement wherein integrated circuit die of varying size, fabrication processes, and function are commonly mounted in the same host wafer using a filled epoxy material of special characteristics. The mounting epoxy material also serves as a substrate for the die interconnecting conductors in regions adjacent the mounted die. The described assembly also includes a newly available photosensitive polyimide material as a planarization and passivation covering for the die and hose wafer and as a mounting surface for an interconnecting metal conductor array. Multiple levels of interconnection metal. Fabrication processes for the die to host wafer attachment …

Hybrid Wafer Scale Microcircuit Integration -- [ 4989063 ], Edward S. Kolesar Jr.

AFIT Patents

A wafer scale integration arrangement wherein integrated circuit die of varying size, fabrication processes, and function are commonly mounted in the same host wafer using a filled epoxy material of special characteristics. The mounting epoxy material also serves as a substrate for the die interconnecting conductors in regions adjacent the mounted die. The described assembly also includes a newly available photosensitive polyimide material as a planarization and passivation covering for the die and host wafer and as a mounting surface for an interconnecting metal conductor array. Multiple levels of interconnection metal. Fabrication processes for the die to host wafer attachment …

Forming Fine Particles, Dennis R. Alexander

Department of Electrical and Computer Engineering: Faculty Publications

To alter feedstock material, the material is exposed to laser radiation applied at a selected angle of incidence, intensity and wavelength related to the refractive index of the feedstock material. Fine uniform particles may be formed through vapor explosion and/or plasma formation and used by this method to coat surfaces, such as with paint or adhesive or to suply uniform small particles to a heat engine. Moreover, moving materials such as a column of liquid may be subjected to high internal pressure and temperature for creating physical and chemical changes.

Visual Speech Training Aid For The Deaf, Subhashri Venkat

Electrical & Computer Engineering Theses & Dissertations

A computer-based vowel articulation training aid has been developed. A "continuous" acoustic-phonetic transformation is performed to map speech parameters to a lower dimensionality display space. There are two possible approaches to this transformation problem. The transformation could be either linear or a combination nonlinear/linear. The nonlinear transformation is performed using a multi-layered feedforward neural network with linear output layers. Speech parameters are extracted either from an analog filter bank arrangement (band energies) or by a digital signal processing procedure (Discrete Cosine Transform Coefficients). The speech parameters obtained from both methods correspond to the spectral envelope of the speech signals. The …

Pulsed Laser Annealing Of Gaas Implanted With Se And Si, Andrzej Rys, Yanan Shieh, Alvin Compann, Huade Yao, Ajit Bhat

Department of Electrical and Computer Engineering: Faculty Publications

Carrier activation and mobility were studied by Raman spectroscopy and the Hall effect in pulsed laser annealed samples of GaAs implanted with doses of Si and Se from 2.2. x 10¹² to 6.0 x 10¹⁴ cm^-2. The samples were annealed using a pulsed XeCl excimer laser ( = 308 nm) and a pulsed dye laser (=728 nm) with energy densities from 0.06 to 0.9 J/cm² and pulse durations of about 10 ns. Very high carrier concentrations of 3 x 10¹⁹ and 1.5 x 10¹⁹ cm^-3 were obtained for the best n-type GaAs …

Metamodeling Aspects Of Model Conceptualization, Wayne W. Wakeland

Complex Systems Faculty Publications and Presentations

This paper suggests a technique for improving the conceptualization of models. The key aspect of this technique is to set aside the main model for a period of time during the model conceptualization process and focus on building a "watchdog" submodel. The primary purpose of the watchdog submodel is to assure that the main model remains internally consistent during its operation. In the experience of this author, such a submodel can help to identify model conceptualization errors and to determine if a model is sufficiently "robust" to adequately replicate the behavior of the system being modeled.

This is not a …

Theoretical Model For The Images Formed By A Spherical Particle In A Coherent Imaging System: Comparison, Scott Alan Schaub, D. R. Alexander, J. P. Barton

Department of Electrical and Computer Engineering: Faculty Publications

A simple theoretical model is presented that allows calculation of the image produced by a spherical absorbing particle illuminated by monochromatic, coherent laser light. Results presented in this paper are restricted to a singe-lens imaging system, although generalization to more complex imaging system configurations would be straightfoward. The method uses classic Lorenz-Mie scattering theory to obtain the electromagnetic field external to an absorbing spherical particle and a Fourier optics approach to calculate the intensities in the image plane. Experimental results evaluating focus characteristics are examined for 50 um diameter water droplets using an N2 laser imaging system in conjunction with …

Parallel Architectures For Solving Combinatorial Problems Of Logic Design, Phuong Minh Ho

Dissertations and Theses

This thesis presents a new, practical approach to solve various NP-hard combinatorial problems of logic synthesis, logic programming, graph theory and related areas. A problem to be solved is polynomially time reduced to one of several generic combinatorial problems which can be expressed in the form of the Generalized Propositional Formula (GPF) : a Boolean product of clauses, where each clause is a sum of products of negated or non-negated literals.

Computation Of Frequency Characteristics Of Lumped-Element 3 Db Branch Line Directional Couplers, H. R. Mgombelo

Tanzania Journal of Engineering and Technology (TJET)

An analysis of the 3 dB lumped-element branchline directional coupler constructed using L-C and T networks is given. Matrices of lumped element capacitances and inductances in the form of low and high pass filters are equated to the matrices of the distributed element transmission lines at the centre frequency of operation, as a result of which design equations are derived. Using even and odd modes of excitation, frequency characteristics of the directional couplers are computed and compared to those of the coupler constructed using distributed element transmission lines.