Made available in DSpace on 2014-06-12T23:02:06Z (GMT). No. of bitstreams: 2 arquivo8221_1.pdf: 6794681 bytes, checksum: 9e21bd693267c06a920d3723dd2c8f78 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / O objetivo deste estudo foi reconhecer as atuais características fisiográficas e sedimentológicas da plataforma continental adjacente ao município de Tamandaré-PE, localizado na Área de Proteção Ambiental Costa dos Corais, através de um mapeamento sonográfico. Foram realizados 20 perfis batimétricos e sonográficos, utilizando-se um sonar de varredura lateral Sea Scan® PC e uma ecossonda GARMIN GPSMAP 185 Sounder. Estes perfis estavam situados a cada 500 m e se estenderam entre as profundidades de 15 e 25 m. 26 amostras de sedimento foram coletadas e submetidas a análises de granulometria e teores de carbonato de cálcio. As imagens acústicas digitais geradas pelo sonar de varredura lateral foram georreferenciadas através de reamostragem e os padrões de eco e textura, bem como os resultados das análises sedimentológicas permitiram identificar e localizar três fundos distintos. A fisiografia submarina da área foi caracterizada por relevos positivos (recifes submersos) e negativos (paleocanal), intercalados por superfícies com declive mais suave. Substratos consolidados indicam que, durante flutuações do nível do mar, provavelmente a linha de costa já esteve a aproximadamente 16, 20 e 22 m abaixo do nível atual. Os fundos (habitats bentônicos) foram classificados como: rochosos, lamosos e arenosos. Este último habitat foi predominante na área amostrada, sendo composto preferencialmente por areias carbonáticas grossas a muito grossas. Os fundos lamosos apresentaram uma distribuição mais restrita, localizados entre as linhas de arenitos de praia observados a 16 e 20 m de profundidade e principalmente junto a uma suave depressão a leste da Baía de Tamandaré. Os ambientes rochosos, representados por tacis e cabeços, ocorreram nas faixas de profundidade de 16, 20 e 22 m. A localização destes habitats é uma contribuição para os programas nacional e global de monitoramento de recifes de coral. Além disso, no caso de fundos lamosos explorados pela pesca do camarão, sua localização é relevante para o levantamento do estoque pesqueiro

Along Sweden’s east coast there are thousands of well-preserved shipwrecks after an extensive shipping that stretches far back in history. The Baltic Sea is a unique sea in the sense that the ship worm Teredo Navalis cannot live here, which means that the ship’s timber is well preserved under water. But we have little knowledge how many these wrecks are and where they are located. No comprehensive underwater inventory like those made on land has even been made. Therefore, these shipwrecks are threatened with destruction by our ignorance of them. By scanning water areas in our immediate environment with Side scan sonar technology, our state of knowledge can be significantly improved. With this method, these relics can be found and preserved as far as possible for future generations. The wrecks can also be used for recreation and experience activities.

In this dissertation an innovative technology to study whale sharks, Rhincodon typus is presented. The Integrated Satellite and Acoustic Telemetry project (iSAT) combines underwater acoustic telemetry, autonomous navigation and radio frequency communications into a standalone system. The whale shark, a resident of the Saudi Arabian Red Sea, is the target of the study. The technology presented is designed to help close current gaps in the knowledge of whale shark biology; these are gaps that prohibit the design of optimal conservation strategies. Unfortunately, the various existing tracking technologies each have limitations and are unable to solve all the unanswered questions. Whale shark populations are increasingly threatened by anthropogenic activities such as targeted and indirect fishing pressure, creating an urgent need for better management practices. This dissertation addresses the current state-of-the-art of relevant technologies, including autonomous surface vehicles (ASVs), sensors for research in the ocean and remote monitoring of wild fauna (biotelemetry). iSAT contains components of all of these technologies, but the primary achievement of this dissertation is the development of iSAT’s Acoustic Tracking System (ATS). Underwater, the most efficient way of transmitting energy through long distances is sound. An electronic tag is attached to an animal and works as its acoustic identifier. iSAT’s hydrophone array detects the presence and direction of the acoustic signal generated by the tag. The expected performance, range, and capacity to tell the direction to the tag are explained and compared to the actual measured values. The first operational iSAT ATS is demonstrated. This work represents significant advancement towards a fully autonomous iSAT system. Developments on the power electronics, navigation, renewable energy harvesting, and other modules are included in this research. With the recent integration of digital acquisition systems, iSAT’s capabilities were increased to minimize its size and allow it to communicate with other acoustic systems. Future engineering works are still necessary to achieve a fully automated system, but the current developments with the ATS have immediate applications.

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A genetic algorithm from literature is adapted to design piezoelectric sonar sensors using results from physics simulations to optimize for a uniform voltage response over a wide range of frequencies. The adapted genetic algorithm produces valid sensor designs, and algorithm improvements are proposed. The best case general methods for bathymetric mapping with a sonar sensor is determined by sweeping various point selection algorithms, interpolation algorithms, and algorithm parameters. A set of methods are proposed based on how many sample points are used and what error metric is preferred. Additional algorithms are suggested for future improvements.

We consider the problem of narrow-band signal detection in a passive sonar environment. The collected signals are passed to a fast Fourier Transform (FFT) delay-sum beamformer. In classical signal detection, the output of the FFT spectrum analyser in each frequency bin is the signal power spectrum which is used as the signal feature for detection. The observed signal power is compared to a locally estimated mean noise power and a log likelihood ratio test (LLRT) can then be established. In this thesis, we propose the use of the power spectral density (PSD) matrix of the spectrum analyser output as the feature for detection due to the additional cross-correlation information contained in such matrices. However, PSD matrices are structurally constrained and therefore form a manifold in the signal space. Thus, to find the distance between two matrices, the measurement must be carried out using Riemannian distance (RD) along the tangent of the manifold, instead of using the common Euclidean distance (ED). In this thesis, we develop methods for measuring the Frechet mean of noise PSD matrices using the RD and weighted RD. Further, we develop an optimum weighting matrix for use in signal detection by RD so as to further enhance the detection performance. These concepts and properties are then used to develop a decision rule for the detection of narrow-band sonar signals using PSD matrices. The results yielded by the new detection method are very encouraging. / Thesis / Master of Applied Science (MASc)

In recent years the United States Navy has concentrated most of its Anti-Submarine Warfare (ASW) research and development efforts toward passive sonar. Its ability to locate enemy targets without being detected gives the passive sonar system a supreme strategic advantage over its active counterpart. One aspect of passive sonar signal processing is the time delay estimation of an underwater acoustic wavefront. From this estimation the location and velocity of the radiating source (target) can then be determined. This report compares two popular methods of estimating time delay utilizing computer simulations of each: the cross correlator and the beamformer.

This thesis focuses on the problem of underwater target tracking with consideration for realistic conditions using active sonar. This thesis addresses the following specific problems: 1) underwater detection in three dimensional (3D) space using multipath detections and an uncertain sound speed profile in heavy clutter, 2) tracking a group of divers whose motion is dependent on each other using sonar detections corrupted by unknown structured background clutter, 3) extended target tracking (ETT) with a high-resolution sonar in the presence of multipath detection and measurement origin uncertainty. Unrealistic assumptions about the environmental conditions may degrade the performance of underwater tracking algorithms. Hence, underwater target tracking with realistic conditions is addressed by integrating the environment-induced uncertainties or constraints into the trackers. First, an iterated Bayesian framework is formulated using the ray-tracing model and an extension of the Maximum Likelihood Probabilistic Data Association (ML-PDA) algorithm to make use of multipath information. With the ray-tracing model, the algorithm can handle more realistic sound speed profile (SSP) instead of using the commonly-assumed constant velocity model or isogradient SSP. Also, by using the iterated framework, we can simultaneously estimate the SSP and target state in uncertain multipath environments. Second, a new diver dynamic motion (DDM) model is integrated into the Probability Hypothesis Density (PHD) to track the dependent motion diver targets. The algorithm is implemented with Gaussian Mixtures (GM) to ensure low computational complexity. The DDM model not only includes inter-target interactions but also the environmental influences (e.g., water flow). Furthermore, a log-Gaussian Cox process (LGCP) model is seamlessly integrated into the proposed filter to distinguish the target-originated measurement and false alarms. The final topic of interest is to address the ETT problem with multipath detections and clutter, which is practically relevant but barely addressed in the literature. An improved filter, namely MP-ET-PDA, with the classical probabilistic data association (PDA) filter and random matrices (RM) is proposed. The optimal estimates can be provided by MP-ET-PDA filter by considering all possible association events. To deal with the high computational load resulting from the data association, a Variational Bayesian (VB) clustering-aided MP-ET-PDA is proposed to provide near real-time processing capability. The traditional Cramer-Rao Lower Bound (CRLB), which is the inverse of the Fisher information matrix (FIM), quantifies the best achievable accuracy of the estimates. For the estimation problems, the corresponding theoretical bounds are derived for performance evaluation under realistic underwater conditions. / Thesis / Doctor of Philosophy (PhD)

The biosonar system of bats has many unique adaptations which allow for navigation in extremely cluttered environments. One such adaptation is the rapid motion of the pinna and noseleaf observed in certain families of old-world bats (Rhinolophidae and Hipposiderae). Little is known about the physical properties about this adaptation affects emitted pulses or incoming echoes. To explore the physical properties of biosonar systems utilizing dynamic peripheries, biomimetic sonar systems have been devised, which can be used to simulate the structural characteristics of the pinna and noseleaf geometry as well as the motor characteristics. Using this method, it was determined that the changing conformations of the biomimetic baffles were responsible for time-variant signatures in echoes. These signatures could be seen in echoes from a variety of both simple and complex target shapes. Then to further the capabilities of the device, an improved actuation system was devised using pneumatic actuation. This allowed for the baffles to make several unique motions as opposed to being restricted to one previously. It was also shown that the distinct motion profiles of the system led to distinct differences in the received acoustic signal. The features encoded by this system could lead to improvements in the development of improved sensing of smaller autonomous systems. GRANT INFORMATION: This work was supported by grants from the Office of Naval Research (ONR) and the Naval Engineering Education Consortium (NEEC). Additional support was provided by an East Asia and Pacific Summer Institutes (EAPSI) fellowship from the National Science Foundation (NSF). / Doctor of Philosophy / Bats are known for using echolocation in addition to sight for hunting and navigating at night. The capabilities of bats and their ``sonar'' systems vary widely, as each species has evolved to survive in its specific environment. Certain species of bats indigenous to Eurasia are observed to perform complex motions of the outer ear and noseleaf (a ridged structure which sits atop the nostrils and acts like a ``megaphone'' of sorts). These bats are noted to be able to live in particularly cluttered environments and could be a particularly useful model organism for improving sonar. This is because since they are able to acquire detailed information about its surroundings with only their nostrils and ears, are able to outperform complicated man-made devices with thousands more sensing elements. To be able to better understand how a fast-moving ear and noseleaf can improve the sonar capabilities of bats, robots which mimic these bats have been devised, with the main purpose being to replicate the sensing elements of the bat. There have been significant changes made to the robotic sonar head in order to allow for us to expand the capabilities of our research. Using CT-scans as reference, the design of the baffles was redesigned to become more realistic and to have more features observed in the bats. A new method was designed in order to move the ``ears'' and ``noseleaf'' of the robot, using pneumatic actuators, which allowed for better control of the system. Finally, prototype sensors were developed to aid in the development of a motion feedback system to ensure a stable system. The robotic sonar has been used in several experiments to study the effects of a fast-moving, flexible anatomy on the physical properties of echoes. This is first illustrated by studying the echoes from various targets with changes in ear and noseleaf shape. Additionally, with the use of the improved actuation system, it was shown that different motion profiles lead to different responses. The continued development of this system and the changes to the signals explored provide new opportunities for furthering the fields of adaptive sensing as they apply to robots and other platforms. Being able to use a few ``smart'' sensors will help reduce the size, power, and weight costs of traditional sensing designs and allow for more robust and efficient technology to be produced.

The initial portion of this thesis examines the problem of tracking a maneuvering target in the 2-dimensional (X,Z) plane, vertical to the ocean floor, using passive time-delay measurements. The target is free to maneuver in velocity and make depth changes at times unknown to the observer. In the past, tracking systems have used Extended Kalman Filters to process the nonlinear measurements, but these have inherent divergence problems. To overcome this, a nonlinear prefilter is added to linearize the measurements and thus allow the use of a conventional Kalman Filter which makes the tracking system more 'robust' and also decouples the depth estimator from the polar range estimator. The depth estimator is discussed in detail here. The latter part of this thesis introduces tracking in the 2-dimensional horizontal (X, Y) plane, parallel to the ocean floor, to observe polar range and target bearing angle. The approach of using a nonlinear prefilter and a standard Kalman Filter is similar to the one described above. Subsequently, the analysis is extended to a Kalman Filter which is not 'matched', i.e. it does not possess any knowledge of the deterministic inputs which cause target motion. This necessitates the use of a bank of Kalman Filters and an adaptive weighting scheme. Test results are included to show that all source maneuvers can be tracked with a relatively high degree of accuracy. / Master of Science