Data adaptive velocity/depth spectra estimation in seismic wide angle reflection analysis

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology July 1977In studying the earth with reflection seismics, one of the major unknowns is the velocity structure of the medium. Techniques used to determine the velocity structure commonly involve multi-channel arrays which measure the spatial as well as the time structure of the returning signals. The application of a data adaptive technique, the Maximum Likelihood Method, to the problem of estimating seismic velocities is described. The peculiar problems of this application are identified and investigated. The windowing of short duration signals is shown to be an important consideration, and the statistics of the MLM estimator for a single observation of the data set are presented. The adaptive estimator is applied to an ideal covariance matrix, to simulated data, and to field data. The results show the MLM velocity/depth estimator to be a valuable tool in seismic analysis, and the windowing and statistical results should have general applications in a variety of fields.This study was supported in part by NSF-IDOE Grant GX-4094, NOAA Contract 04-6-158-44081, ONR Contract N00014-77-6-0266, by a fellowship from the Research Laboratory of Electronics at MIT, and by the MIT/WHOI Joint program in Ocean Engineering

Biologically inspired processing of radar and sonar target echoes

Modern radar and sonar systems rely on active sensing to accomplish a variety of tasks, including detection and classification of targets, accurate localization and tracking, autonomous navigation and collision avoidance. Bats have relied on active sensing for over 50 million years and their echolocation system provides remarkable perceptual and navigational performance that are of envy to synthetic systems. The aim of this study is to investigate the mechanisms bats use to process echo acoustic signals and investigate if there are lessons that can be learned and ultimately applied to radar systems. The basic principles of the bat auditory system processing are studied and applied to radio frequencies. A baseband derivative of the Spectrogram Correlation and Transformation (SCAT) model of the bat auditory system, called Baseband SCAT (BSCT), has been developed. The BSCT receiver is designed for processing radio-frequency signals and to allow an analytical treatment of the expected performance. Simulations and experiments have been carried out to confirm that the outputs of interest of both models are “equivalent”. The response of the BSCT to two closely spaced targets is studied and it is shown that the problem of measuring the relative distance between two targets is converted to a problem of measuring the range to a single target. Nearly double improvement in the resolution between two close scatterers is achieved with respect to the matched filter. The robustness of the algorithm has been demonstrated through laboratory measurements using ultrasound and radio frequencies (RF). Pairs of spheres, flat plates and vertical rods were used as targets to represent two main reflectors

Electric load information system based on non-intrusive power monitoring

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (leaves 192-200).Obtaining high quality information economically and reliably is always a difficult objective to achieve. The electric power industry and consumers recently face many challenges, such as deregulation, autonomous power systems and power quality. The knowledge of the nature and state of the power systems will undoubtedly be the key in meeting these challenges. The Non-Intrusive Power Monitor is a novel attempt to collect such information with a minimal physical installation. Raw voltage and current are measured at a single location to yield harmonic power signals. They typically carry the fingerprints of the electric loads present in a system, and their analysis can produce such information as the operational and diagnostic status of the loads. The power signals can also be used for the system identification, parameter estimation and energy consumption optimization study. In this research, the power signals are mostly modeled as stochastic processes and various detection, estimation and pattern recognition algorithms are developed to extract desired information. A constant load status identifier is developed in this thesis which can identify the ON and OFF status of electric loads, both from their steady-state power consumptions and transient patterns. The identifier can also classify multiple load events occurring at a same time and estimate states without load events. The power consumed by a variable speed drive is also estimated using the correlations between the fundamental powers and higher harmonic powers. The harmonic signal generated by the imbalance of a rotating machine is estimated to monitor the drive, i.e. its speed and magnitude of the imbalance. The algorithms are thoroughly tested using the data collected at real buildings, and some of them are implemented on-line.(cont.) This thesis focuses on developing mathematical models and signal processing algorithms for the customers at the end of the AC distribution system. Its results will directly benefit the developments of a ubiquitous electric meter in a deregulated market, a diagnostic or prognostic tool for mission-critical systems and an intelligent power quality monitor.by Kwangduk Douglas Lee.Ph.D

Least squares-based iterative identification methods for linear-in-parameters systems using the decomposition technique

By extending the least squares-based iterative (LSI) method, this paper presents a decomposition-based LSI (D-LSI) algorithm for identifying linear-in-parameters systems and an interval-varying D-LSI algorithm for handling the identification problems of missing-data systems. The basic idea is to apply the hierarchical identification principle to decompose the original system into two fictitious sub-systems and then to derive new iterative algorithms to estimate the parameters of each sub-system. Compared with the LSI algorithm and the interval-varying LSI algorithm, the decomposition-based iterative algorithms have less computational load. The numerical simulation results demonstrate that the proposed algorithms work quite well

Direction of Arrival Estimation in Low-Cost Frequency Scanning Array Antenna Systems

RÉSUMÉ Cette thèse propose des méthodes d'estimation de la direction d'arrivée (DOA) et d'amélioration de la résolution angulaire applicables aux antennes à balayage de fréquence (Frequency Scanning Antenna ou FSA) et présente un développement analytique et des confirmations expérimentales des méthodes proposées. Les FSA sont un sous-ensemble d'antennes à balayage électronique dont l'angle du faisceau principal change en faisant varier la fréquence des signaux. L'utilisation des FSA est un compromis entre des antennes à balayage de phase (phased arrays antennas) plus coûteuses et plus complexes, et des antennes à balayage mécanique plus lentes et non agiles. Bien que l'agilité et le faible coût des FSA les rendent un choix plausible dans certaines applications, les FSA à faible coût peuvent ne pas être conformes aux exigences souhaitées pour l'application cible telles que les exigences de résolution angulaire. Ainsi, cette recherche tente d'abord de caractériser les capacités de résolution angulaire de certains systèmes d'antennes FSA sélectionnés. Elle poursuit en explorant des modifications ou extensions aux algorithmes de super-résolution capables d'améliorer la résolution angulaire de l'antenne et de les adapter pour être appliqués aux FSA. Deux méthodes d'estimation de la résolution angulaire, l'estimation du maximum de vraisemblance (Maximum Likelihood ou ML) et la formation du faisceau de variance minimale de Capon (Minimum Variance Beamforming ou MVB) sont étudiées dans cette recherche. Les deux méthodes sont modifiées pour être applicables aux FSA. De plus, les méthodes d'étalonnage et de pré-traitement requises pour chaque méthode sont également introduites. Les résultats de simulation ont montré qu'en sélectionnant des paramètres corrects, il est possible d'améliorer la résolution angulaire au-delà de la limitation de la largeur de faisceau des FSA en utilisant les deux méthodes. Les critères pour lesquels chaque méthode fonctionne le mieux sont discutés et l'analyse pour justifier les conditions présentées est donnée.----------ABSTRACT This research investigates direction of arrival (DOA) estimation and angular resolution enhancement methods applicable to frequency scanning antennas (FSA) and provides analytical development and experimental validation for the proposed methods. FSAs are a subset of electronically scanning antennas, which scan the angle of their main beam by varying the frequency of the signals. Using FSA is a trade-off between more expensive and complex phase array antennas and slower and non-agile mechanical scanning antennas. Although agility and low-cost of FSAs make them a plausible choice in some application, low-cost FSAs may not comply with the desired requirements for the target application such as angular resolution requirements. Thus, this research attempts to first characterize the angular resolution capabilities of some selected FSA antenna systems, and then modify or extend super-resolution algorithms capable of enhancing the angular resolution of the antenna and adapt them to be applied to FSAs. Two angular resolution estimation methods, maximum likelihood estimation (ML) and Capon minimum variance beamforming (MVB), are studied in this research. Both methods are modified to be applicable to FSAs. In addition, the calibration and pre-processing methods required for each method are also introduced. Simulation results show that by selecting correct parameters, it is possible to enhance angular resolution beyond the beamwidth limitation of FSAs using both methods. The criteria for which each method performs the best are discussed and an analysis supporting the presented conditions are given. The proposed methods are also validated using the measured antenna radiation pattern of an 8-element FSA which is built based on a composite right/left-handed (CRLH) waveguide. In addition, the experimental results using a beam scanning parabolic reflector antenna using a frequency multiplexed antenna feed is given. The design limitations of this antenna reduces the performance of angular resolution enhancement methods. Therefore, a hybrid scanning system combining mechanical and frequency scanning using the beam scanning reflector antenna is also proposed

Vibration Monitoring: Gearbox identification and faults detection

L'abstract è presente nell'allegato / the abstract is in the attachmen