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Articles 361 - 390 of 402
Full-Text Articles in Electrical and Electronics
An Investigation Of The Application Of Artificial Neural Networks To Adaptive Optics Imaging Systems, Andrew H. Suzuki
An Investigation Of The Application Of Artificial Neural Networks To Adaptive Optics Imaging Systems, Andrew H. Suzuki
Theses and Dissertations
Recurrent and feedforward artificial neural networks are developed as wavefront reconstructors. The recurrent neural network studied is the Hopfield neural network and the feedforward neural network studied is the single layer perceptron artificial neural network. The recurrent artificial neural network input features are the wavefront sensor slope outputs and neighboring actuator feedback commands. The feedforward artificial neural network input features are just the wavefront sensor slope outputs. Both artificial neural networks use their inputs to calculate deformable mirror actuator commands. The effects of training are examined.
Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot
Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot
Theses and Dissertations
This thesis documents the design, fabrication, and testing of a lightweight, planar microwave lens. The lens consists of two planar arrays of lightweight printed circuit antennas interconnected by microstrip lines whose length varies as a function of position on the lens. Microwave energy is coupled from one face of the lens to the other by means of a slot etched in the ground plane. At 8.0 GHz the lens is ten wavelengths across, is less than 1/8 inch thick, and weighs less than 4 pounds. The lens can scan a beam over a +/- 30 degree region in both the …
A Multiple Model Adaptive Estimator Using First And Second-Order Acceleration Models For Use In A Forward-Looking Infrared Tracker, Barbara J. Niblett
A Multiple Model Adaptive Estimator Using First And Second-Order Acceleration Models For Use In A Forward-Looking Infrared Tracker, Barbara J. Niblett
Theses and Dissertations
The performance of a multiple model adaptive estimator (MMAE) for an enhanced correlator/forward-looking-infrared tracker for airborne targets is analyzed in order to improve its performance. Performance evaluation is based on elemental filter selection and MMAE estimation error sizes and trends. The elemental filters are based on either first or second-order acceleration models. Improved filter selection is achieved by using acceleration models that separate the frequency content of acceleration power spectral densities into non- overlapping regions with second-order models versus the more traditional overlapping regions with first-order models. A revised tuning method is presented. The maximum a posteriori (MAP) versus the …
Investigation Of Adaptive Controllers For Puma Trajectory Tracking, Daniel J. Sims
Investigation Of Adaptive Controllers For Puma Trajectory Tracking, Daniel J. Sims
Theses and Dissertations
Two robust model-based controllers and two decentralized adaptive controllers are experimentally evaluated. Algorithm evaluation is motivated by the need for controllers with good high speed tracking under varying payload conditions. The test case is a PUMA-560 robotic manipulator operating over the standard test suite. The model-based controllers are made robust by the addition of either an auxiliary input term or an adaptive feedforward compensator based on Lyapunov Theory. The model-based auxiliary input controller (MBAIC) adapts the gain matrices used in computing an additional torque to be combined with model-based feedforward and PD feedback torques. The adaptive model-based controllers adapt the …
High Frequency Scattering Code In A Distributed Processing Environment, Scott Suhr
High Frequency Scattering Code In A Distributed Processing Environment, Scott Suhr
Theses and Dissertations
Government agencies and academic institutions are very interested programming for concurrent processing to cut computer processing time. However, many of the world's problems have already been coded for conventional serial computers. This research demonstrates the feasibility of modifying existing serial codes for execution in a concurrent processing environment. A electromagnetic scattering prediction code known as NECBSC is incrementally modified to incorporated various levels of concurrent computing. The data processed by the code are completely independent, providing an avenue for data decomposition of the process. Portions of the data set are processed on each mode and the results combined for final …
Development Of A Personal Computer Simulation Program Of The Ln-94 Inertial Navigation System, Thomas E. Flynn
Development Of A Personal Computer Simulation Program Of The Ln-94 Inertial Navigation System, Thomas E. Flynn
Theses and Dissertations
This thesis develops a simulation that emulates a Litton LN-94 INS. Real time simulation is achieved for a stationary navigation case and a straight-and-level flight trajectory are provided to exercise the simulation dynamics. The user interface is simple and requires little previous knowledge to operate. The communication link with the MILSTD 1553B bus provide a realistic environment in which to collect and analyze data. The simulation is processed on an 80386 IBM compatible personal computer. A 23-state INS error model is implemented and integration is performed by a fifth-order Kutta-Merson routine. The simulation is interfaced to a plotting routine and …
An Alternative Algorithm For Discrete-Time Filtering, Frederick H. Zeitz Iii
An Alternative Algorithm For Discrete-Time Filtering, Frederick H. Zeitz Iii
Theses and Dissertations
The discrete-time Kalman filter is a conditional mean estimator of the states of a linear stochastic process, conditioned on the previous state and current measurements. It assumes that the states and noise inputs can be represented as jointly Gaussian random variables. The influence diagram is a decision analysis tool. Under certain conditions, it can represent continuous, jointly Gaussian random variables. The conditioning order of the random variables may be changed (using Bayes' rule) so that any random variable can be conditioned on any other subset of random variables in the diagram. Under these conditions, an influence diagram can represent the …
A Fully Coupled, Automated Formation Control System For Dissimilar Aircraft In Maneuvering Formation Flight, Paul R. Rohs
A Fully Coupled, Automated Formation Control System For Dissimilar Aircraft In Maneuvering Formation Flight, Paul R. Rohs
Theses and Dissertations
This study developed a fully automated formulation control system, capable of controlling a number of like or dissimilar aircraft in maneuvering formation flight. C-130 fixed wing aircraft and H-53 helicopters were modelled in various formulations and simulated through a mix of maneuvers. External formation guidance was assumed as a single data burst of nominal function guidance commands and separation distances for each wing aircraft in the formation. No communication was assumed between formation aircraft. Wing aircraft track lead aircraft maneuvering with an ideal on-board sensor, maneuvering to maintain relative position. It was determined that lead aircraft inputs must be attenuated …
A Navigation Reference System (Nrs) Using Global Positioning System (Gps) Aiding, Richard D. Stacey
A Navigation Reference System (Nrs) Using Global Positioning System (Gps) Aiding, Richard D. Stacey
Theses and Dissertations
To quantify the performance abilities of existing or proposed navigation systems, the U.S. Air Force has for the last several years compared the performance of the system under test to the performance of a baseline navigation system known as the Completely Integrated Reference Instrumentation System (CIRIS). CIRIS obtains a highly accurate navigation solution by combining the output from three major subsystems: inertial navigation system (INS) information, barometric altitude information, and range and range-rate data from ground transponders which have been precisely surveyed. Although the navigation solution produced by CIRIS is highly accurate, it will soon be inadequate as the standard …
Rule-Based Frequency Domain Speech Coding, Vance M. Mcmillan
Rule-Based Frequency Domain Speech Coding, Vance M. Mcmillan
Theses and Dissertations
A speech processing system is designed to simulate the transmission of speech signals using a speech coding scheme. The transmitter portion of the simulation extracts a minimized set of frequencies in Fourier space which represents the essence of each of the speech timeslices. These parameters are then adaptively quantized and transmitted to a receiver portion of the coding scheme. The receiver then generates an estimate of the original timeslice from the transmitted parameters using a sinusoidal speech model. After initial design, the thesis investigates how each of the design parameters affect the human perceived quality of speech. This is done …
Implementation Of The Modified Monte Carlo Technique Using Importance Sampling On The Block Oriented System Simulator, John B. Bennett
Implementation Of The Modified Monte Carlo Technique Using Importance Sampling On The Block Oriented System Simulator, John B. Bennett
Theses and Dissertations
The purpose of this thesis was to implement the Modified Monte Carlo technique using Importance Sampling on the Block Oriented System Simulator (BOSS). Computer simulation techniques of communications systems were reviewed. Next, conventional Monte Carlo techniques and Modified Monte Carlo techniques using Importance Sampling were reviewed. Models of Binary Phase Shift Keying (BPSK) systems using both Monte Carlo techniques were implemented and simulated. Reasons for the model using Importance Sampling not working correctly are postulated. The Monte Carlo technique is a method of ensuring the an inherently infinite procedure, such as determining system bit error rate (BER), can be determined …
Predicting The Performance Of Airborne Antennas In The Microwave Regime, David P. Carroll
Predicting The Performance Of Airborne Antennas In The Microwave Regime, David P. Carroll
Theses and Dissertations
This study investigated the application of a high-frequency model (Uniform Geometrical Theory of Diffraction) of electromagnetic sources mounted on a curved surface of a complex structure. In particular, the purpose of the study was to determine if the model could be used to predict the radiation patterns of cavity-backed spiral antennas mounted on aircraft fuselages so that the optimum locations for the antennas could be chosen during the aircraft design phase. A review of literature revealed a good deal of work in modeling communications, navigation, identification antennas (blade monopoles and aperture slots) mounted on a wide variety of aircraft fuselages …
Network Reduction Using Error Prediction, Michael V. Gilsdorf
Network Reduction Using Error Prediction, Michael V. Gilsdorf
Theses and Dissertations
This thesis investigates gradient descent learning algorithms for multi-layer feed forward neural networks. A technique is developed which uses error prediction to reduce the number of weights/nodes in a network. The research begins by studying the first and second order back-prop training algorithms along with their convergence properties. A network is reduced by making an estimate of the amount of error which would occur when a weight(s) is removed. This error estimate is then used to determine if a particular weight is essential to the operation of the network. If not, it is removed and the network retrained. The process …
A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin
A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin
Theses and Dissertations
This study presents a method of moments solution for the surface currents and charge distributions on an aperture-fed, stacked patch antenna. To make the solution independent of the antenna excitation technique, an aperture magnetic current distribution is assumed, and the spatial Green's functions of the antenna are used to calculate the tangential fields on the antenna patches and coefficients for a finite series expression of the surface currents and charge densities. The Green's functions of the antenna are modeled with polynomials that are a function of the radial distance separating observer and source locations. The method of moments solution is …
Gabor Filters And Neural Networks For Segmentation Of Synthetic Aperture Radar Imagery, Albert P. L'Homme
Gabor Filters And Neural Networks For Segmentation Of Synthetic Aperture Radar Imagery, Albert P. L'Homme
Theses and Dissertations
This research investigates Gabor filters and artificial networks for autonomous segmentation of 1 foot by 1 foot) high resolution polarimetric synthetic aperture radar (SAR). Processing involved frequency correlation between the SAR imagery and biologically motivated Gabor functions. Methods for selecting the Gabor tuning parameters from the endless choices of frequency, rotation, standard deviation and bandwidth are discussed. Using these parameters, resulting Gabor correlation images were reduced in speckle, and more detailed. This research used cosine Gabor functions and operated on single polarization HH magnitude data. Following selection of the appropriate Gabor features, multiple Gabor representations were generated and converted for …
Kalman Filter Tracking Of A Reflective Target Using Forward Looking Infrared Measurements And Laser Illumination, Roger J. Evans
Kalman Filter Tracking Of A Reflective Target Using Forward Looking Infrared Measurements And Laser Illumination, Roger J. Evans
Theses and Dissertations
This thesis investigates Kalman filter tracking of a missile hardbody, at a range of 2,000 kilometers, using forward looking infrared (FLIR) measurements and low-energy laser illumination of the missile hardbody. A missile reflectivity model provides realism in the simulation. The tracking scenario uses one filter, provided with FLIR measurements, to estimate the intensity centroid location of the missile's plume. A second, independent, filter estimates the center-of-mass of the missile hardbody. The center-of-mass measurements provided to this filter are computed from information gathered by scanning a low-energy laser along the first filter's estimate of the missile velocity vector. Single scans of …
The Radar Range Equation For The Detection Of Steady Targets In Weibull Clutter, Leon C. Rountree
The Radar Range Equation For The Detection Of Steady Targets In Weibull Clutter, Leon C. Rountree
Theses and Dissertations
In this thesis, the detection characteristics of a steady target immersed in radar clutter characterized by returns statistically modeled according to a Weibull probability density function are developed. A detector model is developed by modifying an envelope detection scheme used to detect deterministic signals in Gaussian noise. By examining the statistics of the detector output under alternate hypotheses, an expression for the probability of detection (P sub d) is developed in terms of the probability of false alarm (P sub fa), the signal-to-clutter ratio (SCR), and the Weibull skewness parameter (b), which is a function of the type of terrain …
Pulsed Compression For Aerosol Ranging With Coherent Pulse-Doppler Lidar Systems, Jerry L. Rogers
Pulsed Compression For Aerosol Ranging With Coherent Pulse-Doppler Lidar Systems, Jerry L. Rogers
Theses and Dissertations
This thesis provides a thorough review of conventional matched filter radar theory as it applies to aerosol sensing lidar. Basic matched-filter radar theory and the complex, dense aerosol target model eventually lead to a general derivation of the matched-filter radar receiver response to a dense aerosol target environment. The matched-filter response is obtained in terms of a two dimensional convolution of the target scattering function and the radar ambiguity function. The range and radial velocity resolution of various radar signals were compared using the matched-filter radar receiver and scattering function models. Pulse compression radar signals were compared to the simple …
Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders
Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders
Theses and Dissertations
The purpose of this study was to begin development of an Inverse Synthetic Aperture Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will …
Speech Coding And Compression Using Wavelets And Lateral Inhibitory Networks, Richard Ricart
Speech Coding And Compression Using Wavelets And Lateral Inhibitory Networks, Richard Ricart
Theses and Dissertations
The purpose of this thesis is to introduce the concept of lateral inhibition as a generalized technique for compressing time/frequency representations of electromagnetic and acoustical signals, particularly speech. This requires at least a rudimentary treatment of the theory of frames-which generalizes most commonly known time/frequency distributions--the biology of hearing, and digital signal processing. As such, this material, along with the interrelationships of the disparate subjects, is presented in a tutorial style. This may leave the mathematician longing for more rigor, the neurophysiological psychologist longing for more substantive support of the hypotheses presented, and the engineer longing for a reprieve from …
Digital Control Of The Utah/Mit Dexterous Hand: Initial Evaluation And Analysis, Lloyd W. Rainey Iii
Digital Control Of The Utah/Mit Dexterous Hand: Initial Evaluation And Analysis, Lloyd W. Rainey Iii
Theses and Dissertations
An experimental digital platform is developed as an environment on which to evaluate digital control strategies for dexterous manipulation with a pneumatically actuated tendon-driven manipulator. This environment is used to begin the study of advanced control methods that are suitable for providing the tracking accuracy required for grasping and dexterous manipulation with a pneumatically actuated tendon-driven end-effector. The digital platform consists of a PC/AT-386 and a single board MC68020 microcomputer in a VME chassis with shared RAM between the two processors to control the Utah/MIT Dexterous Hand (UMDH). The MC68020 controls the A/D and D/A access for the UMDH, while …
Te Scattering From A Dielectric Coated Conducting Strip, William D. Wood Jr.
Te Scattering From A Dielectric Coated Conducting Strip, William D. Wood Jr.
Theses and Dissertations
Consider a plane wave incident on a conducting strip of infinite length coated on one side with a thin, uniform coating of lossless dielectric, and let the incident magnetic field vector be parallel to the edges of the strip. From first principles we develop the integral equations relating the total, incident, and scattered fields in the dielectric. We expand the fields in the dielectric slab as the sum of three plane waves (the 'forced' wave and two oppositely-directed surface waves). The phase constants in the x and y directions are known and the wave amplitudes are found using least-squared- error-point-matching. …
Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck
Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck
Theses and Dissertations
The multilayer perceptron was extensively analyzed. A technique for analyzing the multilayer perceptron, the saliency measure, was developed which provides a measure of the importance of inputs. The method was compared to the conventional statistical technique of best features and shown to provide similar rankings of the input. Using the saliency measure, it is shown that the multilayer perceptron effectively ignores useless inputs and that whether it is trained using backpropagation or extended Kalman filtering, the weighting of the inputs is the same. The backpropagation training algorithm is shown to be a degenerate version of the extended Kalman filter. The …
Feasibility Analysis Of Developing A Formal Performance Model Of Ada Tasking, Kathryn J. Edwards
Feasibility Analysis Of Developing A Formal Performance Model Of Ada Tasking, Kathryn J. Edwards
Theses and Dissertations
As software system requirements become more complex, software engineers must carefully design the systems to ensure the systems to ensure the systems adequately meet all requirements, both functional and non-functional. Because real-time systems have timing constraints, in addition to the more traditional behavioral constraints, a comprehensive software design analysis model is required which incorporate performance, timing, and behavioral constraints. Although the Ada language tasking constructs are compiler independent, Ada tasking is dependent on its runtime environment; therefore, a formal model of Ada tasking and its associated runtime environment is important in order for system designers to make realistic decisions when …
Moving-Bank Multiple Model Adaptive Estimation And Control Applied To A Large Flexible Space Structure, Robert B. Moyle
Moving-Bank Multiple Model Adaptive Estimation And Control Applied To A Large Flexible Space Structure, Robert B. Moyle
Theses and Dissertations
The performance of moving-bank multiple model adaptive estimation (MMAE) and control (MMAC) algorithms for large space structure control is analyzed in this thesis. The performance of a six-state filter model and associated controller are evaluated on the basis of estimation/control performance against a 24-estate truth model. A model developed using finite element analysis is used to approximate a large flexible space structure. The space structure is configured as a two-bay truss which is attached to a large central hub, where the mass of the hub is considered to be much more larger than the mass of the flexible structure. The …
Characterization Of Radar Signals Using Neural Networks, Daniel R. Zahirniak
Characterization Of Radar Signals Using Neural Networks, Daniel R. Zahirniak
Theses and Dissertations
Recent work concerning artificial neural networks has focused on decreasing network training times. Kernel Classifier networks, using radial basis functions (RBFs) as the kernel function, can be trained quickly with little performance degradation. Short training times are critical for systems which must adapt to changing environments. The function of Kernel Classifier networks is based on the principle that multivariate functions can be approximated via linear combinations of RBFs. RBFs can also perform probability density estimations, making classifications approximating a Baye's optimal descriminant. Methods used to set the RBF centers included matching the training data, Kohonen Training, K-Means Clustering and placement …
Analysis And Testing Of A Bistatic Radar Cross Section Measurement Capability For The Afit Anechoic Chamber, Timothy D. Mccool
Analysis And Testing Of A Bistatic Radar Cross Section Measurement Capability For The Afit Anechoic Chamber, Timothy D. Mccool
Theses and Dissertations
This research effort examined the feasibility of performing bistatic radar cross section (RCS) measurements in the AFIT anechoic chamber. The capability was established to measure the bistatic RCS of a target versus frequency and versus target azimuth angle. In either case, one of three bistatic angles (angle between transmit and receive antennas) is available: 45 degrees, 90 degrees, and 135 degrees. Accurate bistatic RCS measurements were obtained using a CW radar and utilizing background subtraction, bistatic calibration, and software range gating. Simple targets were selected for validation purposes since their bistatic RCS could be predicted. These consisted of spheres and …
Establishment Of A Fabrication And Measurement Capability For Aperture-Fed Stacked Patch Microstrip Antennas At The Air Force Institute Of Technology, Christopher I. Terry
Establishment Of A Fabrication And Measurement Capability For Aperture-Fed Stacked Patch Microstrip Antennas At The Air Force Institute Of Technology, Christopher I. Terry
Theses and Dissertations
Much time and effort has been applied to accurately model aperture- fed stacked patch microstrip antennas at the Air Force Institute of Technology (AFIT). The results of this study provide AFIT with the capability to fabricate and measure these antennas for comparison of measured radiation characteristics to the predicted characteristics. Basic microstrip patch antenna theory is reviewed, as well as the motivation leading to the development of aperture-fed stacked patch microstrip antennas. The fabrication process used to produce the two antennas manufactured for this study is described in detail. The construction of a small anechoic chamber for pattern measurements is …
Angle Of Arrival Detection Through Artificial Neural Network Analysis Of Optical Fiber Intensity Patterns, Scott Thomas
Angle Of Arrival Detection Through Artificial Neural Network Analysis Of Optical Fiber Intensity Patterns, Scott Thomas
Theses and Dissertations
The optical sensors of United States Air Force reconnaissance vehicles, such as satellites, are subject to temporary or permanent blinding from hostile (or threat) laser radiation. By detecting and determining the angle of arrival (AOA) of the hostile radiation, the reconnaissance vehicle may be able to protect its optical sensors by taking evasive maneuvers or by shutting down the optical sensor (such as closing a shutter) until the threat has passed. In addition, the vehicle can relay information to its ground terminal allowing the intelligence community to determine the source of the hostile laser radiation. This thesis demonstrated that an …
An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning
An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning
Theses and Dissertations
The purpose of this thesis was to design and develop an expert system shell in Ada, and to evaluate the shell's execution and size performance to determine its suitability for real-time operation on the MIL-STD-1750A embedded flight processor. The expert system shell uses the CLIPS/Ada inference engine, a forward-chaining Ada implementation of Rete. The expert system shell design is presented along with an overview of the target environment--the MIL-STD-1750A VHSIC Avionic Modular Processor (VAMP) running under the Ada Avionics Real-Time Software (AARTS) Operating System. Theoretical and empirical complexity analyses of the inference engine are presented and discussed in view of …