Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures. The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques. The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.

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In speech communication systems such as voice-controlled systems, hands-free mobile telephones and hearing aids, the received signals are degraded by room reverberation and background noise. This degradation can reduce the perceived quality and intelligibility of the speech, and decrease the performance of speech enhancement and source localization. These problems are difficult to solve due to the colored and nonstationary nature of the speech signals, and features of the Room Impulse Response (RIR) such as its long duration and non-minimum phase. In this dissertation, we focus on two topics of speech enhancement and speaker localization in noisy reverberant environments. A two-stage speech enhancement method is presented to suppress both early and late reverberation in noisy speech using only one microphone. It is shown that this method works well even in highly reverberant rooms. Experiments under different acoustic conditions confirm that the proposed blind method is superior in terms of reducing early and late reverberation effects and noise compared to other well known single-microphone techniques in the literature. Time Difference Of Arrival (TDOA)-based methods usually provide the most accurate source localization in adverse conditions. The key issue for these methods is to accurately estimate the TDOA using the smallest number of microphones. Two robust Time Delay Estimation (TDE) methods are proposed which use the information from only two microphones. One method is based on adaptive inverse filtering which provides superior performance even in highly reverberant and moderately noisy conditions. It also has negligible failure estimation which makes it a reliable method in realistic environments. This method has high computational complexity due to the estimation in the first stage for the first microphone. As a result, it can not be applied in time-varying environments and real-time applications. Our second method improves this problem by introducing two effective preprocessing stages for the conventional Cross Correlation (CC)-based methods. The results obtained in different noisy reverberant conditions including a real and time-varying environment demonstrate that the proposed methods are superior compared to the conventional TDE methods. / Graduate / 0544 / 0984 / saeed.mosayyebpour@gmail.com

Dans le cadre du projet européen SESAR, la nécessité d'accroître la capacité du trafic aérien a motivé la planification de trajectoires avions 4D (espace + temps). Afin de mettre en place une planification pré-tactique (évitement de zones avec une mauvaise météo ou congestionnées pour un avion) et de mettre en place une planification tactique (générer des ensembles de trajectoires 4D sans conflit), nous introduisons un nouvel algorithme : l'algorithme de propagation de la lumière (APL). Cet algorithme est basé sur une méthode de propagation de front d'onde qui s'inspire de l'analogie avec la propagation de la lumière et qui est adapté au problème de planification de trajectoires. L'APL donne des résultats satisfaisant pour une journée de trafic réel sur la France tout en satisfaisant les contraintes spécifiques à la gestion du trafic aérien. L'APL a ensuite été adapté pour prendre en compte les incertitudes qui concernent la vitesse réelle des avions. Ainsi adapté aux incertitude, l'APL a été testé sur la même journée de trafic avec mise en place de points RTA (Real Time Arrival). Les points RTA permettent de réduire l'incertitude dans le cas où l'APL n'arrive pas à résoudre les conflits. Les résultats obtenus sont très encourageants.

In speech communication systems such as voice-controlled systems, hands-free mobile telephones and hearing aids, the received signals are degraded by room reverberation and background noise. This degradation can reduce the perceived quality and intelligibility of the speech, and decrease the performance of speech enhancement and source localization. These problems are difficult to solve due to the colored and nonstationary nature of the speech signals, and features of the Room Impulse Response (RIR) such as its long duration and non-minimum phase. In this dissertation, we focus on two topics of speech enhancement and speaker localization in noisy reverberant environments. A two-stage speech enhancement method is presented to suppress both early and late reverberation in noisy speech using only one microphone. It is shown that this method works well even in highly reverberant rooms. Experiments under different acoustic conditions confirm that the proposed blind method is superior in terms of reducing early and late reverberation effects and noise compared to other well known single-microphone techniques in the literature. Time Difference Of Arrival (TDOA)-based methods usually provide the most accurate source localization in adverse conditions. The key issue for these methods is to accurately estimate the TDOA using the smallest number of microphones. Two robust Time Delay Estimation (TDE) methods are proposed which use the information from only two microphones. One method is based on adaptive inverse filtering which provides superior performance even in highly reverberant and moderately noisy conditions. It also has negligible failure estimation which makes it a reliable method in realistic environments. This method has high computational complexity due to the estimation in the first stage for the first microphone. As a result, it can not be applied in time-varying environments and real-time applications. Our second method improves this problem by introducing two effective preprocessing stages for the conventional Cross Correlation (CC)-based methods. The results obtained in different noisy reverberant conditions including a real and time-varying environment demonstrate that the proposed methods are superior compared to the conventional TDE methods. / Graduate / 2015-04-23 / 0544 / 0984 / saeed.mosayyebpour@gmail.com

[pt] No cenário atual das telecomunicações móveis, os arranjos de antenas voltaram a receber grande atenção dos pesquisadores, especialmente quando esquemas adaptativos de modificação de seus diagramas de radiação são utilizados. Uma das aplicações que exploram o potencial dos arranjos de antenas é o seu uso como forma de aumentar consideravelmente a eficiência espectral dos sistemas móveis atuais e da próxima geração. A outra aplicação em evidência está voltada para sistemas de localização de posição, pois algumas das técnicas conhecidas envolvem a estimação de ângulos-de-chegada usando arranjos de antenas. Diante destas possibilidades, cresce em importância o estudo das variações do canal de propagação rádio móvel no domínio em que o uso dos arranjos de antenas atua: o espacial. O presente trabalho procura contribuir para o contexto em questão, com uma investigação experimental do canal real rádio-móvel nos domínios temporal (retardos) e espacial (ângulos-de-chegada). No que se refere ao contexto nacional, contribuições similares baseadas em simulações já são encontradas; baseadas em medidas não. Em particular, sondagens na faixa de 1,8 GHz em ambientes internos típicos foram realizadas. Duas técnicas distintas de sondagem temporalespacial foram implementadas, tomando por base uma sonda de canal faixa-larga montada e testada com sucesso, como contribuição principal de uma dissertação de mestrado recentemente apresentada por um integrante do mesmo grupo de pesquisa ao qual esta tese está vinculada. Uma das técnicas sintetiza o arranjo realizando as sondagens com uma única antena que é sucessivamente deslocada para ocupar as posições correspondentes às dos elementos do arranjo. A outra técnica emprega um arranjo real. Em ambas, a configuração mais simples para um arranjo foi utilizada: a linear uniforme. As sondagens não forneciam diretamente os espectros espaciais-temporais. As estimativas dos espectros foram processadas posteriormente, aplicando técnicas como o correlograma para o domínio do retardo, e quatro técnicas distintas para o domínio espacial, que foi o foco principal deste trabalho: duas convencionais; e duas paramétricas, com potencial de aumentar a resolução das estimativas, assumindo hipóteses razoáveis sobre as respostas esperadas. De posse das respostas espectrais estimadas, comparações com estimativas teóricas permitiram uma análise de desempenho das técnicas utilizadas. Adicionalmente à investigação experimental do canal espacial, procurou-se verificar o potencial da aplicação da teoria de wavelets ao estudo do canal rádiomóvel. Em especial, uma das principais aplicações daquela teoria foi testada como técnica de pós-processamento das respostas espectrais no domínio do retardo. A supressão de ruído por decomposição wavelet foi aplicada a um vasto conjunto de medidas de canal disponíveis, fruto de trabalhos anteriores do grupo de pesquisa ao qual esta tese está vinculada, com resultados expressivos. / [en] In the present mobile communications scenario, researchers have turned once again special attention to antennae arrays, particularly when adaptive schemes are employed to modify its radiation patterns. One of its main applications results in considerable increases to the spectral efficiency of present and next generation mobile systems. The other major application is headed towards position location systems, since some of the known techniques comprise angle-of-arrival estimation using antennae arrays. Under such possibilities, mobile radio propagation channel variations studies grow in relevance, specially regarding the antennae arrays main domain of action: the spatial domain. The present work tries to contribute to the overstated context, experimentally investigating the actual mobile radio channel over the temporal (delays) and spatial (angles of arrival) domains. Regionally speaking, similar contributions based on simulations are already found, but none based on measurements. In special, 1.8 GHz indoor soundings have been carried out. Two different temporal spatial sounding techniques have been deployed, based on na available wideband channel sounder successfully assembled and tested as the major contribution of a MSc. dissertation recently presented by a member of the same research team to which this thesis belongs. One of such techniques sinthesyzes the array carrying the sounding out with a single antenna, which is successively moved to occupy the spots corresponding to the array elements. The other method employs an actual array. For both cases, the simplest array configuration has been used: the uniform linear one. Space-time spectra were not directly available in real time during the soundings. Its estimates have been processed later, applying techniques such as the correlogram over the delay domain, and four distinct methods over the spatial domain, the main focus of the present work. Two conventional methods have been used, as well as two parametric ones, potentially capable to increase the estimates resolution, assuming reasonable hypotheses regarding the expected responses. With the estimated spectral responses in hands, comparisons with theoretical estimates allowed a performance assessment of the employed methods. In addition to the spatial channel experimental investigation, the wavelets theory potential of application to the mobile-radio channel study has been checked out. Notably, one of the wavelets theory major applications has been tested as a post-processing technique to improve delay-domain spectral responses. Wavelet decomposition based de-noising has been applied to a huge measurements ensemble, available as the product of previous works of the research group to which this thesis is attached, leading to remarkable results.

Dans l'océan, les changements de température induisent des perturbations de la vitesse de propagation des ondes acoustiques. La tomographie acoustique océanique utilise les fluctuations de signaux acoustiques enregistrés pour cartographier ces perturbations de vitesse du son. Cette étude propose une méthode alternative utilisant la direction de propagation des ondes acoustiques (plutôt que les temps de propagation utilisés classiquement) pour imager un guide d'onde océanique peu profond (~100 m), petite échelle (1 à 10 km), avec une haute résolution spatiale (10 m horizontalement, 2 m en profondeur). Dans ce contexte, les ondes acoustiques basse fréquence (~1 kHz) à large bande spectrale (~1.5 kHz) se propagent selon des trajectoires multiples assimilables à des rayons géométriques épais spatialement. L'utilisation d'un couple d'antennes (émission/réception) et de la double formation de voies permet de séparer les signaux en provenance des différents trajets acoustiques et de mesurer leur : temps de propagation (TP), direction d'arrivée (DA) et direction de départ (DD). Dans l'hypothèse de faibles perturbations, les variations des TP, DA et DD sont reliées linéairement aux perturbations de la distribution de vitesse du son de manière analytique. Cette formulation, basée sur la physique de la diffraction de Born au 1er ordre, utilise des fonctions noyaux appelées : noyaux de sensibilité temps-angles (NSTA). Les méthodes classiques d'inversion permettent alors de retrouver les perturbations de vitesse à partir des variations de TP, DA et DD en utilisant les NSTA. Les méthodes développées ont été validées sur données simulées, puis appliquées à des données réelles d'expériences à échelle réduites réalisées dans la cuve ultrasonore de l'ISTerre, Grenoble. / In the ocean, temperature changes induce sound-speed perturbations. Ocean acoustic tomography uses the fluctuations of recorded acoustic signals, to map those sound-speed perturbations. To this end, sound-speed perturbations are classically related to the acoustic-wave travel-times measured on the records. This study suggests an alternative method to perform acoustic thermometry based on acoustic-wave propagation directions. It allows imaging a shallow-water waveguide (~100 m), at small scale (1 to 10 km), with high spatial resolution (10 m in range, 2 m in depth). In this context, wideband (~1.5 kHz) low frequency (~1 kHz) acoustic waves propagates along multiple paths similar to spatially « fat » geometrical rays. Using a pair of arrays (source/receiver) and the double-beamforming processing to separate acoustic signals coming from different paths and measure their: travel-time (TT), directions-of-arrival (DOA) and directions-of-departure (DOD). Under the hypothesis of small perturbations, TP, DOA and DOD variations are linearly related to sound-speed perturbations in an analytical way. This formulation based on Born's diffraction physics at the first order uses kernel functions called: the time-angle sensitivity kernels (T-A-SK). The T-A-SK model is then combined to classical inversion methods to retrieve sound-speed perturbations from TT, DOA and DOD variations. The methods developed here have been validated on simulated data, and applied on real small-scale data coming from the ultrasonic tank of the ISTerre, Grenoble.

[pt] A estimação de direção de chegada (DoA) é uma importante área de processamento de arranjos de sensores que é encontrada em uma ampla gama de aplicações de engenharia. Este fato, juntamente com o desenvolvimento da área de Compressed Sensing (CS) nos últimos anos, são a principal motivação desta dissertação. Nesta dissertação, é apresentada uma formulação do problema de estimação de direção de chegada como um problema de representação esparsa da sinal e vários algoritmos de recuperação esparsa são derivados e investigados para resolver o problema atual. Os algoritmos propostos são baseados na incorporação da informação prévia sobre o sinal esparso no processo de estimativa. Na primeira parte, nos concentramos no desenvolvimento de dois algoritmos Bayesianos , que se baseiam principalmente no algoritmo iterative hard thresholding (IHT). Devido ao desempenho inferior dos algoritmos convencionais de estimação de chegada em cenários com fontes correlacionadas, nós prestamos atenção especial ao desempenho dos algoritmos propostos nesta condição. Na segunda parte, o problema de otimização baseados na minimização da norma l1 é apresentado e um algoritmo bayesiano é proposto para resolver o problema chamado basis pursuit denoising (BPDN). Os resultados da simulação mostram que os estimadores Bayesianos superam os estimadores não Bayesianos e que a incorporação do conhecimento prévio da distribuição do sinal melhorou substancialmente o desempenho dos algoritmos. / [en] Direction of arrival (DoA) estimation is a key area of sensor array processing which is encountered in a broad range of important engineering applications. This fact together with the development of the Compressed Sensing (CS) area in the last years are the principal motivation of this thesis. In this dissertation, a formulation of the source localization problem as a sparse signal representation problem is presented and several sparse recovery algorithms are derived and investigated for solving the current problem. The proposed algorithms are based on the incorporation of the prior information about the sparse signal in the estimation process. In the first part, we focus on the development of two Bayesian greedy algorithms which are principally based on the iterative hard thresholding (IHT) algorithm. Due to the inferior performance of the conventional DoA estimation algorithm in scenarios with correlated sources, we pay special attention to the performance of the proposed algorithms under this condition. In the second part, the optimization problem using a l1 penalty is introduced and a Bayesian algorithm for solving the basis pursuit denoising problem is presented. Simulation results shows that Bayesian estimators which take into account the prior knowledge of the signal distribution outperform and improve substantially the performance of the non-Bayesian estimators.

Dans les décennies à venir, la connaissance d’informations très précises concernant la position d’un objet permettra de créer des applications révolutionnaires dans les domaines sociaux, médicaux, commerciaux et militaires. La technologie Ultra-Wideband (UWB) est considérée comme un bon candidat permettant de fournir des capacités de localisation précise grâce à la mesure de l’estimation du temps d'arrivée (TOA). Dans cette thèse, des algorithmes de mesure de distance dans le cas multi-utilisateurs pour des systèmes UWB sont étudiés afin d'atteindre une bonne précision pour une faible complexité, avec de la robustesse aux interférences multi-utilisateur et dans le cas d’un grand nombre d'utilisateurs. Au cours de la dernière décennie, les signaux chaotiques ont reçu une attention significative en raison d'un certain nombre de caractéristiques intéressantes. Les signaux chaotiques sont des signaux non périodiques, déterministes ou considérés comme pseudo-aléatoires provenant de systèmes dynamiques non linéaires. Leur bonne autocorrélation et leurs faibles propriétés d’inter corrélation les rendent particulièrement résistants aux évanouissements par trajets multiples et capables d'atténuer les interférences multi-utilisateur (MUI). En raison de leur grande sensibilité aux conditions initiales, il est possible de générer un grand nombre de signaux chaotiques pour accroître la capacité globale du système. Dans cette thèse, deux nouveaux algorithmes d'estimation de TOA sont proposés dans un cadre multi-utilisateur avec une faible complexité et une bonne robustesse. Le nombre d'utilisateurs pris en charge par ces deux algorithmes est beaucoup plus grand que dans le cas des estimateurs de TOA actuels. Cependant, l'utilisation de séquences d'étalement classique et d’impulsion limite l'amélioration des performances et la capacité du système. Afin d’apporter des améliorations, des signaux chaotiques sélectionnés sont utilisés comme séquences d'étalement ou impulsion dans les algorithmes proposés. Grâce à l'utilisation de signaux chaotiques, notre algorithme est non seulement amélioré, mais permet également l’utilisation d’un plus grand nombre d'utilisateurs par comparaison avec l’algorithme utilisant des signaux classiques / In the coming decades, highly accurate position information has the potential to create revolutionary applications in the social, medical, commercial and military areas. Ultra-Wideband (UWB) technology is considered as a potential candidate for enabling accurate localization capabilities through Time-of-Arrival (TOA) based ranging techniques. Over the past decade, chaotic signals have received significant attention due to a number of attractive features. Chaotic signals are aperiodic, deterministic, and random-like signals derived from nonlinear dynamical systems whose good autocorrelation, low cross-correlation and sensitivity to the initial conditions make them particularly suitable to ranging systems. In this thesis, two new multiuser TOA estimation algorithms are proposed with low complexity and robustness to MUI, the number of users supported by which is much larger than current multiuser TOA estimators. While, the use of classic spreading sequences and ranging pulse constrain the further improvement of ranging performance and system capacity. For breaking through the limit brought by the classic signals, the selected chaotic signals are employed as the spreading sequences or ranging pulse in our proposed algorithms. With the use of chaotic signals, our proposed algorithm not only obtains the additional improvement, but also with capability to support larger number of users comparing with its counterpart using classic signals