Electrical and Computer Engineering Commons^™

Induction Machine Broken-Bar Fault Diagnosis Using The Rotor Magnetic Field Space-Vector Orientation, Behrooz Mirafzal, Nabeel Demerdash

Electrical and Computer Engineering Faculty Research and Publications

A new technique based on rotor magnetic field space vector orientation is presented to diagnose broken-bar faults in induction machines operating at steady state. In this technique, stator currents and voltages are used as inputs to compute and subsequently observe the rotor magnetic field orientation, which has a more significant "swing-like" pendulous oscillation in case of broken-bar faults than in healthy operation. It will be shown here that the range of this "pendulous oscillation" is a function of the number of broken bars. Also in this technique, it was found that an inter-turn shorted stator-winding fault, which exhibits similar pendulous …

Optimal Calibration Of Pet Crystal Position Maps Using Gaussian Mixture Models, Kelly A. Stronger, Michael T. Johnson

Electrical and Computer Engineering Faculty Research and Publications

A method is developed for estimating optimal PET gamma-ray detector crystal position maps, for arbitrary crystal configurations, based on a binomial distribution model for scintillation photon arrival. The approach is based on maximum likelihood estimation of Gaussian mixture model parameters using crystal position histogram data, with determination of the position map taken from the posterior probability boundaries between mixtures. This leads to minimum probability of error crystal identification under the assumed model.

Effect Of Stochastic Dead Space On Noise In Avalanche Photodiodes, Oh-Hyun Kwon, Majeed M. Hayat, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

A stochastic dead-space model for impact ionization is developed and used to study the effect of the soft nature of the ionization capability of carriers on the excess noise factor of avalanche photodiodes. The proposed model is based on the rationale that the gradual, or soft, transition in the probability density function (PDF) for the distance from birth to impact ionization can be viewed as that resulting from uncertainty in the dead space itself. The resulting soft PDF, which is parameterized by a tunable softness parameter, is used to establish the limitations of the existing hard-threshold ionization models in ultrathin …

Optimized Breakdown Probabilities In Al/Sub 0.6/Ga/Sub 0.4/As-Gaas Heterojunction Avalanche Photodiodes, Oh-Hyun Kwon, Majeed M. Hayat, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

Recently, it has been shown that the noise characteristics of heterojunction Al/sub 0.6/Ga/sub 0.4/As-GaAs avalanche photodiodes (APDs) can be optimized by proper selection of the width of the Al/sub 0.6/Ga/sub 0.4/As layer. Similar trends have also been shown theoretically for the bandwidth characteristics. The resulting noise reduction and potential bandwidth enhancement have been attributed to the fact that the high bandgap Al/sub 0.6/Ga/sub 0.4/As layer serves to energize the injected electrons, thereby minimizing their first dead space in the GaAs layer. We show theoretically that the same optimized structures yield optimal breakdown-probability characteristics when the APD is operated in Geiger …

The Effect Of Pruning And Compression On Graphical Representations Of The Output Of A Speech Recognizer, Yang Liu, Mary P. Harper, Michael T. Johnson, Leah H. Jamieson

Electrical and Computer Engineering Faculty Research and Publications

Large vocabulary continuous speech recognition can benefit from an efficient data structure for representing a large number of acoustic hypotheses compactly. Word graphs or lattices have been chosen as such an efficient interface between acoustic recognition engines and subsequent language processing modules. This paper first investigates the effect of pruning during acoustic decoding on the quality of word lattices and shows that by combining different pruning options (at the model level and word level), we can obtain word lattices with comparable accuracy to the original lattices and a manageable size. In order to use the word lattices as the input …

Diagnostics Of Eccentricities And Bar/End-Ring Connector Breakages In Polyphase Induction Motors Through A Combination Of Time-Series Data Mining And Time-Stepping Coupled Fe-State Space Techniques, John F. Bangura, Richard J. Povinelli, Nabeel Demerdash, Ronald H. Brown

Electrical and Computer Engineering Faculty Research and Publications

This paper develops the foundations of a technique for detection and categorization of dynamic/static eccentricities and bar/end-ring connector breakages in squirrel-cage induction motors that is not based on the traditional Fourier transform frequency-domain spectral analysis concepts. Hence, this approach can distinguish between the "fault signatures" of each of the following faults: eccentricities, broken bars, and broken end-ring connectors in such induction motors. Furthermore, the techniques presented here can extensively and economically predict and characterize faults from the induction machine adjustable-speed drive design data without the need to have had actual fault data from field experience. This is done through the …

A New Temporal Pattern Identification Method For Characterization And Prediction Of Complex Time Series Events, Richard J. Povinelli, Xin Feng

Electrical and Computer Engineering Faculty Research and Publications

A new method for analyzing time series data is introduced in this paper. Inspired by data mining, the new method employs time-delayed embedding and identifies temporal patterns in the resulting phase spaces. An optimization method is applied to search the phase spaces for optimal heterogeneous temporal pattern clusters that reveal hidden temporal patterns, which are characteristic and predictive of time series events. The fundamental concepts and framework of the method are explained in detail. The method is then applied to the characterization and prediction, with a high degree of accuracy, of the release of metal droplets from a welder. The …

Scene-Based Nonuniformity Correction For Focal Plane Arrays By The Method Of The Inverse Covariance Form, Sergio N. Torres, Jorge E. Pezoa, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

What is to our knowledge a new scene-based algorithm for nonuniformity correction in infrared focal-plane array sensors has been developed. The technique is based on the inverse covariance form of the Kalman filter (KF), which has been reported previously and used in estimating the gain and bias of each detector in the array from scene data. The gain and the bias of each detector in the focal-plane array are assumed constant within a given sequence of frames, corresponding to a certain time and operational conditions, but they are allowed to randomly drift from one sequence to another following a discrete-time …

Kalman Filtering For Adaptive Nonuniformity Correction In Infrared Focal-Plane Arrays, Sergio N. Torres, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

A novel statistical approach is undertaken for the adaptive estimation of the gain and bias nonuniformity in infrared focal-plane array sensors from scene data. The gain and the bias of each detector are regarded as random state variables modeled by a discrete-time Gauss–Markov process. The proposed Gauss–Markov framework provides a mechanism for capturing the slow and random drift in the fixed-pattern noise as the operational conditions of the sensor vary in time. With a temporal stochastic model for each detector’s gain and bias at hand, a Kalman filter is derived that uses scene data, comprising the detector’s readout values sampled …

Breakdown Probabilities For Thin Heterostructure Avalanche Photodiodes, Majeed M. Hayat, Ünal Sako ̆Glu, Oh-Hyun Kwon, Shuling Wang, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The recurrence theory for the breakdown probability in avalanche photodiodes (APDs) is generalized to heterostructure APDs that may have multiple multiplication layers. The generalization addresses layer-boundary effects such as the initial energy of injected carriers as well as the layer-dependent profile of the dead space in the multiplication region. Reducing the width of the multiplication layer serves to both downshift and sharpen the breakdown probability curve as a function of the applied reverse-bias voltage. In structures where the injected carriers have an initial energy that is comparable to the ionization threshold energy, the transition from linear mode to Geiger-mode is …

Optimal Excess Noise Reduction In Thin Heterojunction Al0.6Ga0.4As-Gaas Avalanche Photodiodes, Oh-Hyun Kwon, Majeed M. Hayat, Shuling Wang, Joe C. Campbell, Archie L. Holmes, Yi Pan, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

It has been recently found that the initial-energy effect, which is associated with the finite initial energy of carriers entering the multiplication region of an avalanche photodiode (APD), can be tailored to reduce the excess noise well beyond the previously known limits for thin APDs. However, the control of the initial energy of injected carriers can be difficult in practice for an APD with a single multiplication layer. In this paper, the dead-space multiplication recurrence theory is used to show that the low noise characteristics associated with the initial-energy effect can be achieved by utilizing a two-layer multiplication region. As …

Scene-Based Nonuniformity Correction For Focal Plane Arrays By The Method Of The Inverse Covariance Form, Sergio N. Torres, Jorge E. Pezoa, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

What is to our knowledge a new scene-based algorithm for nonuniformity correction in infrared focal-plane array sensors has been developed. The technique is based on the inverse covariance form of the Kalman filter (KF), which has been reported previously and used in estimating the gain and bias of each detector in the array from scene data. The gain and the bias of each detector in the focal-plane array are assumed constant within a given sequence of frames, corresponding to a certain time and operational conditions, but they are allowed to randomly drift from one sequence to another following a discrete-time …

Diagnostics Of Bar And End-Ring Connector Breakage Faults In Polyphase Induction Motors Through A Novel Dual Track Of Time-Series Data Mining And Time-Stepping Coupled Fe-State Space Modeling, Richard J. Povinelli, John F. Bangura, Nabeel Demerdash, Ronald H. Brown

Electrical and Computer Engineering Faculty Research and Publications

This paper develops the fundamental foundations of a technique for detection of faults in induction motors that is not based on the traditional Fourier transform frequency domain approach. The technique can extensively and economically characterize and predict faults from the induction machine adjustable speed drive design data. This is done through the development of dual-track proof-of-principle studies of fault simulation and identification. These studies are performed using our proven Time Stepping Coupled Finite Element-State Space method to generate fault case data. Then, the fault cases are classified by their inherent characteristics, so-called “signatures” or “fingerprints.” These fault signatures are extracted …

Boundary Effects On Multiplication Noise In Thin Heterostructure Avalanche Photodiodes: Theory And Experiment [Al/Sub 0.6/Ga/Sub 0.4/As/Gaas], Majeed M. Hayat, Oh-Hyun Kwon, Shuling Wang, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the …

An Algebraic Algorithm For Nonuniformity Correction In Focal-Plane Arrays, Bradley M. Ratliff, Majeed M. Hayat, Russell C. Hardie

Electrical and Computer Engineering Faculty Research and Publications

A scene-based algorithm is developed to compensate for bias nonuniformity in focal-plane arrays. Nonuniformity can be extremely problematic, especially for mid- to far-infrared imaging systems. The technique is based on use of estimates of interframe subpixel shifts in an image sequence, in conjunction with a linear-interpolation model for the motion, to extract information on the bias nonuniformity algebraically. The performance of the proposed algorithm is analyzed by using real infrared and simulated data. One advantage of this technique is its simplicity; it requires relatively few frames to generate an effective correction matrix, thereby permitting the execution of frequent on-the-fly nonuniformity …

Maximum-Likelihood Image Estimation Using Photon-Correlated Beams, Majeed M. Hayat, Muhammad Sajjad Abdullah, Adel Joobeur, Bahaa E.A. Saleh

Electrical and Computer Engineering Faculty Research and Publications

A theory is presented addressing the fundamental limits of image estimation in a setup that uses two photon-correlated beams. These beams have the property that their photon arrivals, as a point process, are ideally synchronized in time and space. The true image represents the spatial distribution of the optical transmittance (or reflectance) of an object. In this setup, one beam is used to probe the image while the other is used as a reference providing additional information on the actual number of photons impinging on the object. This additional information is exploited to reduce the effect of quantum noise associated …

Gain-Bandwidth Characteristics Of Thin Avalanche Photodiodes, Majeed M. Hayat, Oh-Hyun Kwon, Yi Pan, Paul P. Sotirelis, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The frequency-response characteristics of avalanche photodiodes (APDs) with thin multiplication layers are investigated by means of a recurrence technique that incorporates the history dependence of ionization coefficients. In addition, to characterize the autocorrelation function of the impulse response, new recurrence equations are derived and solved using a parallel computer. The mean frequency response and the gain-bandwidth product are computed and a simple model for the dependence of the gain-bandwidth product on the multiplication-layer width is set forth for GaAs, InP, Al/sub 0.2/Ga/sub 0.8/As, and In/sub 0.52/Al/sub 0.48/As APDs. It is shown that the dead-space effect leads to a reduction (up …

Projection-Based Image Registration In The Presence Of Fixed-Pattern Noise, Ernest Armstrong, Stephen C. Cain, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

A computationally efficient method for image registration is investigated that can achieve an improved performance over the traditional two-dimensional (2-D) cross-correlation-based techniques in the presence of both fixed-pattern and temporal noise. The method relies on transforming each image in the sequence of frames into two vector projections formed by accumulating pixel values along the rows and columns of the image. The vector projections corresponding to successive frames are in turn used to estimate the individual horizontal and vertical components of the shift by means of a one-dimensional (1-D) cross-correlation-based estimator. While gradient-based shift estimation techniques are computationally efficient, they often …

Locating Target At High Speed Using Image Decimation Decomposition Processing, Zikuan Chen, Mohammad Rezaul Karim, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

We develop a decimation-decomposition processing technique that consists of judiciously selecting certain decimation-decomposed components of an image and then performing inter-component processing. For a (k_x,k_y)-decimation decomposition, there may be up to k_xk_y decimation-decomposed components. The minimal surviving and maximal non-surviving lengths associated with inter-component processing algorithm allows for clutter suppression. By removing detection redundancies, one can locate the target at high speed. A “where-then-what” model is proposed for target tracking and recognition. It locates the target by-image decimation-decomposition processing first and then recognizes the target in question using a suitable image recognition technique.

Impact-Ionization And Noise Characteristics Of Thin Iii-V Avalanche Photodiodes, Mohammad A. Saleh, Majeed M. Hayat, Paul P. Sotirelis, Archie L. Holmes, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

It is, by now, well known that McIntyre's localized carrier-multiplication theory cannot explain the suppression of excess noise factor observed in avalanche photodiodes (APDs) that make use of thin multiplication regions. We demonstrate that a carrier multiplication model that incorporates the effects of dead space, as developed earlier by Hayat et al. provides excellent agreement with the impact-ionization and noise characteristics of thin InP, In/sub 0.52/Al/sub 0.48/As, GaAs, and Al/sub 0.2/Ga/sub 0.8/As APDs, with multiplication regions of different widths. We outline a general technique that facilitates the calculation of ionization coefficients for carriers that have traveled a distance exceeding the …

Breakdown Voltage In Thin Iii-V Avalanche Photodiodes, Mohammad A. Saleh

Electrical and Computer Engineering Faculty Research and Publications

1. The dead-space multiplication theory of Hayat et al. [Journal of Lightwave Technology 10, 1415 (1992)], in conjunction with the multiplication-width-independent ionization-coefficient model developed by Saleh et al. [IEEE Trans. Electron Devices 47, 625 (2000)], are shown to accurately predict breakdown voltages for thin avalanche photodiodes of GaAs, InP, In_0:52Al_0:48As, and Al_0:2Ga_0:8As, over a broad range of device widths. The breakdown voltage is determined from the analytical expression for the impulse-response-function decay rate.

A New Approach For Computing The Bandwidth Statistics Of Avalanche Photodiodes, Majeed M. Hayat, Guoquan Dong

Electrical and Computer Engineering Faculty Research and Publications

A new approach for characterizing the avalanche-buildup-time-limited bandwidth of avalanche photodiodes (APDs) is introduced which relies on the direct knowledge of the statistics of the random response time. The random response time is the actual duration of the APD’s finite buildup-limited random impulse response function. A theory is developed characterizing the probability distribution function (PDF) of the random response time. Recurrence equations are derived and numerically solved to yield the PDF of the random response time. The PDF is then used to compute the mean and the standard deviation of the bandwidth. The dependence of the mean and the standard …

On The Assessment Of Stability And Patterning Of Speech Movements, Anne Smith, Michael T. Johnson, Clare Mcgillem, Lisa Goffman

Electrical and Computer Engineering Faculty Research and Publications

Speech requires the control of complex movements of orofacial structures to produce dynamic variations in the vocal tract transfer function. The nature of the underlying motor control processes has traditionally been investigated by employing measures of articulatory movements, including movement amplitude, velocity, and duration, at selected points in time. An alternative approach, first used in the study of limb motion, is to examine the entire movement trajectory over time. A new approach to speech movement trajectory analysis was introduced in earlier work from this laboratory. In this method, trajectories from multiple movement sequences are time- and amplitude-normalized, and the STI …

Stochastic Stability Of The Continuous-Time Extended Kalman Filter, K. Reif, S. Gunther, Edwin E. Yaz, R. Unbehauen

Electrical and Computer Engineering Faculty Research and Publications

he error behaviour of the extended Kalman filter is analysed. It is proved that the estimation error remains bounded if the system satisfies a detectability condition and both the initial estimation error and the disturbing noise terms are small enough. Moreover, some selected cases with both bounded and unbounded estimation error are demonstrated by numerical simulations.

Scene-Based Nonuniformity Correction With Video Sequences And Registration, Russell C. Hardie, Majeed M. Hayat, Earnest Armstrong, Brian Yasuda

Electrical and Computer Engineering Faculty Research and Publications

We describe a new, to our knowledge, scene-based nonuniformity correction algorithm for array detectors. The algorithm relies on the ability to register a sequence of observed frames in the presence of the fixed-pattern noise caused by pixel-to-pixel nonuniformity. In low-to-moderate levels of nonuniformity, sufficiently accurate registration may be possible with standard scene-based registration techniques. If the registration is accurate, and motion exists between the frames, then groups of independent detectors can be identified that observe the same irradiance (or true scene value). These detector outputs are averaged to generate estimates of the true scene values. With these scene estimates, and …

Theory Of Photon Coincidence Statistics In Photon-Correlated Beams, Majeed M. Hayat, Sergio N. Torres, Leno M. Pedrotti

Electrical and Computer Engineering Faculty Research and Publications

The statistics of photon coincidence counting in photon-correlated beams is thoroughly investigated considering the effect of the finite coincidence resolving time. The correlated beams are assumed to be generated using parametric downconversion, and the photon streams in the correlated beams are modeled by two partially correlated Poisson point processes. An exact expression for the mean rate of coincidence registration is developed using techniques from renewal theory. It is shown that the use of the traditional approximate rate, in certain situations, leads to the overestimation of the actual rate. The error between the exact and approximate coincidence rates increases as the …

An Analytical Approximation For The Excess Noise Factor Of Avalanche Photodiodes With Dead Space, Majeed M. Hayat, Zikuan Chen, Mohammad Rezaul Karim

Electrical and Computer Engineering Faculty Research and Publications

Approximate analytical expressions are derived for the mean gain and the excess noise factor of avalanche photodiodes including the effect of dead space. The analysis is based on undertaking a characteristic-equation approach to obtain an approximate analytical solution to the existing system of recurrence equations which characterize the statistics of the random multiplication gain. The analytical expressions for the excess noise factor and the mean gain are shown to be in good agreement with the exact results obtained from numerical solutions of the recurrence equations for values of the dead space reaching up to 20% of the width of the …

Reduction Of Quantum Noise In Transmittance Estimation Using Photonecorrelated Beams, Majeed M. Hayat, Adel Joobeur, Bahaa E.A. Saleh

Electrical and Computer Engineering Faculty Research and Publications

The accuracy of optical measurements at low light levels is limited by the quantum noise of the source and by the random nature of the interaction with the measured object. The source noise may be reduced by use of nonclassical photon-number squeezed light. This paper considers the use of two photon-correlated beams (generated, for example, by spontaneous parametric downconversion) to measure the optical transmittance of an object. The photons of each beam obey a random Poisson process, but are synchronized in time. One beam is used to probe the object while the other is used as a reference providing information …

Immittance Spectroscopy Of Smart Components And Novel Devices, Mohammad Anwarul Alim, Sanjida Khanam, Martin A. Seitz

Electrical and Computer Engineering Faculty Research and Publications

AC small-signal immittance spectroscopy is employed as a viable tool to demonstrate electrical characterization, performance improvement, and quality assurance issues of smart materials-based components and novel devices. The variation in the ac response, complemented via dc measurements within a range of tolerating temperature, delineates competing phenomena occurring in the microstructures of these engineering material systems. The results are presented in a generic manner with possible explanations on the mechanisms for two selected Debye-like (nearly ideal) and non-Debye (non-ideal) low-capacitance resistors. This spectroscopic approach allows systematic development of a representative equivalent circuit, considered to be the characteristic of the devices and …

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.