ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / Providing normal telemetry behavior predictions prior to and post launch will help to stop surprise catastrophic satellite and spacecraft equipment failures. In-orbit spacecraft fail from surprise equipment failures that can result from not having normal telemetry behavior available for comparison with actual behavior catching satellite engineers by surprise. Some surprise equipment failures lead to the total loss of the satellite or spacecraft. Some recovery actions from a surprise equipment failure increase spacecraft risk and involve decisions requiring a level of experience far beyond the responsible engineers.

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Providing normal telemetry behavior predictions prior to and post launch will help to stop surprise catastrophic satellite and spacecraft equipment failures. In-orbit spacecraft fail from surprise equipment failures that can result from not having normal telemetry behavior available for comparison with actual behavior catching satellite engineers by surprise. Some surprise equipment failures lead to the total loss of the satellite or spacecraft. Some recovery actions as a consequence of a surprise equipment failure are high risk and involve decisions requiring a level of experience far beyond the responsible engineers.

The work presented in this thesis investigates novel transducer implementations that take advantage of directional sensing and generation of acoustic waves. These transducers are conceived by exploiting a Fourier-based design methodology. The proposed devices find application in the broad field of Structural Health Monitoring (SHM), which is a very active research area devoted to the assessment of the structural integrity of critical components in aerospace, civil and mechanical systems. Among SHM schemes, Guided Waves (GWs) testing has emerged as a prominent option for inspection of plate-like structures using permanently attached piezoelectric transducers. GWs-based methods rely on the generation and sensing of elastic waves to evaluate structural integrity. They offer an effective method to estimate location, severity and type of damage. It is widely acknowledged among the GWs-SHM community that effective monitoring of structural health is facilitated by sensors and actuators designed with ad hoc engineered capabilities. The objective of this research is to design innovative piezoelectric transducers by specifying their electrode patterns in the Fourier domain. Taking advantage of the Fourier framework, transducer design procedures are outlined and tailored to relevant SHM applications, such as (i) directional actuation and sensing of GWs, (ii) simultaneous sensing of multiple strain components with a single device, and (iii) estimation of the location of impact sites on structural components. The proposed devices enable significant reductions in cost, hardware, and power requirements for advanced SHM schemes when compared to current technologies.

Single frame ultrasound B-mode image quality is largely governed by the ability to focus the ultrasound beam over a range in depths both in transmission and reception. By developing a comprehensive understanding of acoustic wave propagation two signal processing methods were identified for solving the transmission problem. We made use of both the impulse response using the classical point spread function (PSF) and the spatial sensitivity function (SSF) which describes the spatial distribution at a particular time. Using the angular spectrum method, an accurate analytical model was developed for the field distribution arising from a finite geometry, apodized and focused, plane piston transducer. While there is a thorough understanding of the radiated field arising from uniformly excited plane piston transducers, the focused equivalent (i.e., one that allows a continuous change in phase over the plane piston surface) is incomplete and assumes the Fresnel approximation. Our model addresses the effects of diffraction and evanescent waves without the use of the Fresnel approximation and is applicable at all near- and far-field locations in a lossless medium. The model was analyzed to identify new insights into wave propagation and compared with the Fresnel approximation and the spherically-focused, concave transducer. The piston transducer model was then extended to an attenuating and dispersive medium. After analysing existing models of power-law frequency dependent attenuation, a causal, spherical wave Green’s function was derived from the Navier-Stokes equation for a classical viscous medium. Modifications to the angular spectrum method were presented and used to analyze the radiated field of a focused, planar piston transducer. Finally, after presenting our signal processing strategy for improving imaging spatial resolution through minimization of the SSF, two signal processing methods were derived and analysed in simulation: a deconvolution technique to remove the effects of the ultrasound excitation wave and suppress additive noise from the received ultrasound signal, and a retrospective transmit focusing method that changed the response from a predefined transmit focus to an arbitrary transmit focal depth. Proof-of-concept simulations were presented using a variable number of scatterers and compared with the traditional matched filtering and envelope detection technique.

We present a novel two-dimensional (2D) MAET scanner, with a rotating object of interest and two fixed pairs of electrodes. Such an acquisition scheme, with our novel reconstruction techniques, recovers the boundaries of the regions of constant conductivity uniformly well, regardless of their orientation. We also present a general image reconstruction algorithm for the 2D MAET in a circular chamber with point-like electrodes immersed into the saline surrounding the object. An alternative linearized reconstruction procedure is developed, suitable for recovering the material interfaces (boundaries) when a non-ideal piezoelectric transducer is used for acoustic excitation. The work of the scanner and the linearized reconstruction algorithm is demonstrated using several phantoms made of high-contrast materials and a biological sample.

Aujourd’hui, avec l’envolée mondiale du prix du pétrole, la question énergétique est devenue un sujet d’importance et la possibilité d’exploiter l’énergie ambiante connaitun regain d’attention. Ainsi dans cette thèse, nous nous intéressons aux dispositifs de récupération d’énergie piézoélectrique de vibration dont l’objectif final est de réaliser un réseau de capteurs sans fil (WSN) autonome de faible consommation d’énergie. L’idée est dans un premier temps de prolonger la durée de vie de la batterie, puis dans un second temps de rendrele capteur totalement autonome d’un point de vu énergétique. Les dispositifs actuels étant basés sur la vibration d’une poutre (résonateur mécanique), ils ne sont efficaces qu’à la résonance, avec une faible bande-passante. Ainsi dans ce travail, nous avons tout d’abord proposé une technique de décalage de la fréquence de résonance à l’aide de capacités commutées, cette techniqueréalise un ajustement de la fréquence de résonance en fonction de la fréquence de la source d’excitation et ainsipermetune augmentation de la puissance de sortie. Cette technique a été implémentée avec succès sur un module de capteur WSN avec transmissiond’un signal RF. Toujours dans l’objectif d’agrandir la bande-passante, un résonateur hybride (piézoélectrique/magnétique) bistable associé à une interface électrique (SSHI) a été proposé.Cenouveau et intéressant concept de combiner le résonateur hybride avec une interface à commutation de la tension piézoélectrique a montré, à l’aide de résultats expérimentaux et de simulation,que la puissance est augmentée sur une large bande passante.De plus, afin de rendre le système totalement autonome et de commander les interrupteurs de l’interface électriqueaux instants optimaux, une technique de détection du passage par zéro de la vitesse de vibration a été proposée. Les résultats montrent de bonnes performancesde cette méthode sur toutes lesinterfaces et résonateurs.Contrairement à la méthode classique de détection de la tension crête, la détection du passage par zéro de la vitesse est plus précise. La récupération d’énergie piézoélectrique engendrant un amortissement de la source vibrante, il est possible d’utiliser les mêmes interfaces électriques pour réaliser l’amortissement semi-passif de vibrations de structures mécaniques. Il s’agit d’extraire le maximum d’énergie de la structure en vibration à l’aide de l’élément piézoélectrique. Ainsi, afin de rendre les interfaces électriques pour l’amortissement (SSHD) totalement autonomes, nous avons proposé d’associer la récupération d’énergie piézoélectrique à l’amortissement de structure. L’avantage majeur est qu’il est seulement nécessaire de sacrifier légèrementles performances de l’amortissement pour rendre le système totalement autonome. Les performances ainsi que les limites de cette technique ont été analysées. / Nowadays with the world oil price soaring, the energy issue is becoming a significant topic and the possibility of harvesting ambient energy receiving much attention. In this dissertation, the main topic surrounds improving the piezoelectric energy harvesting device in several aspects and the final objective is to integrate it with low power consumption device, for example a wireless sensor network (WSN) node to extend the battery lifetime and further supply the energy to device directly. Based on the high mechanical quality factor of the structure, the output power of the piezoelectric energy harvesting device will decrease rapidly when the exciting frequency is out of the resonant frequency range. The tunable resonant frequency technique is proposed to broaden the resonant frequency range and increase the output power effectively. Then this technique is successfully combined with a WSN module to transmit the RF signal. To broaden resonant frequency another method is proposed, based on a bistable vibrating cantilever beam and a switching-type interface circuit (SSHI). It's a new and interesting concept to combine these two techniques. The magnets are used to make mechanical behavior non-linear and increase the output power at non-resonance. The SSHI technique through zero-velocity detection can work well when system is driven in non-linear system. The experimental and simulation results through work-cycles discussion show good performance of combining these two techniques. In the interface circuit design, synchronized switching harvesting on an inductor (SSHI) have been verified a successful technique to increase output power in low-coupling system. In order to make use of the SSHI technique in the real application, the velocity control self-powered SSHI (V-SSHI) system is proposed. Unlike the conventional peak detector technique, the zero-velocity detection is used to make the switching time more accurate. The energy flow is separated into three paths to construct the V-SSHI and the experimental results show good performance. When the system is not low-coupled, the SSHI technique will damp vibration.This technique is called SSDI (synchronized switching damping on an inductor). Based on the self-powered technique and zero-velocity detection used in the V-SSHI, these techniques are further applied in structural damping to construct a self-powered SSDI (SP-SSDI). The major advantage is that it is only necessary to sacrifice a small amount of damping performance to make the system fully self-powered. The theoretical analysis and experiment results of time domain comparison and frequency response testing show the limit and performance of the SP-SSDI technique. The SP-SSDI system is a like a feedback loop system and when the displacement is over the limit the SP-SSDI will effectively damp the vibration.

Approved for public release; distribution in unlimited. / Optical turbulence plays an important role in the propagation of electromagnetic waves through the atmosphere because it broadens and distorts the optical beam. A variety of optical, thermal, and acoustic instruments are used to detect the atmospheric turbulence and an acoustic echosounder has proven to be a valuable tool to probe the fine dynamic structure of atmospheric turbulence within first hundred meters above the surface. The first planar acoustic echosounder constructed at the Naval Postgraduate School was by Weingartner and Wroblewski, under Walters' supervision. Moxcey later modified this design by reducing the number of drivers from 25 to 19 and placing the drivers closer together into a hexagonal, close-packed array. This thesis explored the potential sources of the transducer ringing and implemented solutions to the problem. Additionally, we also improved the receiving sensitivity of the echosounder and lowered the electronics noise when receiving. Finally, we applied these techniques to another array assembled with new drivers to improve its performance compared to the previous echosounder array, while measuring and quantifying the level of improvement achieved. / Lieutenant Commander, Republic of China Navy

Threaded fastener is one of the most common ways to join components. Having a method to test threaded fasteners is key when designing a joint and even more a nutrunner. A joint is often tightened by a torque applied on the head. The applied torque is equal to three quantities in the joint, the thread torque, the underhead torque and the clamp force. To measure these quantities are the propose of a friction test rig. A test rig was built last year to be able to do that in a flexible and effective way. But the test rig built last year does not have the possibility to measure the underhead torque. A new transducer is constructed to add that possibility. The transducer is constructed by using methods such as concept generation, strength calculations, FEM simulations and a comparison of sensors are made. An easy way to change the stiffness is also investigated but no possible solution could be found. Some modifications and trims are also done on the test rig and also a comparison with the older BLM rig. A validation is made of how good the rig perform is also done. The results shows in favour for the FTR but precise results is not possible to determine.

Le Réacteur à Haut Flux (RHF) de l'Institut Laue-Langevin (ILL), uniquement dédié à la recherche fondamentale, produit le flux continu de neutrons thermiques le plus intense au monde, soit 1.5 1015 neutrons par seconde et par cm2, avec une puissance thermique de 58 MW. Ce réacteur possède un cœur constitué d'un élément combustible unique en uranium très enrichi. Dans le cadre d'une étude sur le comportement des éléments combustibles après irradiation, l'ILL souhaite développer un dispositif capable d'aller mesurer la largeur du canal d'eau. Cette mesure permettra de caractériser le gonflement des plaques, inhérent à l'irradiation, ainsi que les modifications de structure (corrosion, décollement,…). Cependant, cette mesure de distance est délicate puisqu'une résolution de l'ordre du micromètre est recherchée alors que la dimension de l'espace inter-plaques est proche du millimètre. Les contraintes d'accès sont également difficiles du fait que l'élément combustible est placé à environ 5 m sous la surface de l'eau. En outre, tous les systèmes sont soumis à de fortes radiations. Basés sur des méthodes magnétiques, capacitives ou optiques, des dispositifs permettent aujourd'hui de mesurer des distances avec une résolution nanométrique et avec des fonctionnalités pouvant être adaptées dans des conditions de températures et de pression difficiles. Ces méthodes ne peuvent cependant pas être appliquées à des systèmes fortement radiatifs ou en immersion. Afin de répondre à cette problématique, deux transducteurs ultrasonores fonctionnant en émission-réceptions ont été conçus, étudiés et ensuite développés dans le cadre de cette thèse. Ces transducteurs sont montés sur une lame en acier inoxydable de 1 mm d'épaisseur afin d'autoriser l'accès à l'espace inter-plaques. Du fait de la haute résolution recherchée, les transducteurs sont excités à une fréquence au-delà de 120 MHz et intégrés dans un ensemble d'instruments de mesure comprenant un système d'acquisition haute fréquence, un traitement de signal de haute précision et une électronique spécifique développée pour améliorer le signal d'excitation.Connaissant la vitesse du son dans l'eau et l'épaisseur de la lame, les transducteurs mesurent la distance inter-plaque à partir de la détermination du temps de vol entre l'émission d'un pulse ultrasonore et la réception des échos réfléchis sur la surface de chacune des plaques. Deux expériences in-situ conduisant à une série de mesure de distance inter-plaque ont été réalisées au sein de l'élément combustible irradié du réacteur à haut flux. / The fuel elements of High Performance and Research Reactors are usually made of plates instead of rods. During irradiation, the fuel plates undergo limited swelling and an oxide layer appears on the outer surface of the cladding. However, measuring the inter-plate distance of such fuel elements isn't trivial mainly because of the requested resolution in constraint geometry. Indeed while the typical dimensions of the water channel between plates is close to two millimeter, a resolution of one micron is needed to characterize any fuel plate swelling. In order to perform such measurements, we designed a robust device based upon high frequency ultrasonic probes and adapted to the high radiation environment. It was thinned until 1 mm in order to be inserted into the 1.8 mm width water channel. To achieve the expected resolution, the system is excited with frequencies up to 120 MHz. Thanks to a highly performing signal processing; distance measurement is carried out through the ultrasonic waves' time of flight. One of the crucial points is then the evaluation of the local water temperature inside the water channel. To obtain a precise estimation of this parameter, the ultrasonic sensor is used as a thermometer thanks to the analysis of the spectral components of the acoustic signal propagating inside the sensor multilayered structure. The feasibility of temperature and distance measurement has already been proved with success on a full size irradiated fuel element of the RHF. Some experimental constraints were identified to improve the accuracy of the measurement system in future works.

A modelagem do campo acústico gerado por um transdutor ultra-sônico retangular é importante porque sua geometria é usada freqüentemente por transdutores multielementos (arrays). O conhecimento do campo acústico pode otimizar alguns parâmetros de projeto de transdutores ultra-sônicos, tais como: a sua geometria, a profundidade de foco, a largura do feixe acústico, bem como os parâmetros de focalização de um array (leis de retardos e de apodização). O modelo implementado neste trabalho calcula a pressão acústica e o potencial de velocidade gerados por transdutores de geometria retangular em um conjunto de pontos do espaço. A abordagem usa o método da integral de convolução e da resposta espacial impulsiva, cuja solução computacional do problema é exata e relativamente simples, o que normalmente não ocorre com outros métodos que apresentam um alto custo computacional (tempo de processamento). A resposta em pressão do transdutor em cada ponto do espaço é obtida com o modelo implementado em Matlab e é verificada experimentalmente. São realizadas medidas experimentais do campo de pressão gerado por transdutores retangulares monoelementos na faixa de freqüências de 400 kHz a 2,2 MHz e um array na freqüência de 1 MHz, em um tanque de imersão, utilizando um hidrofone pontual e um sistema computadorizado de varredura de campo. A comparação entre os resultados simulados e experimentais mostra uma boa concordância, bem como as suas limitações. / The simulation of the acoustic field generated by a rectangular ultrasonic transducer is important because its geometry is frequently used in arrays. The knowledge of the acoustic field can optimize some design parameters of ultrasonic transducers, such as: geometry, focus depth, acoustic beam width, as well as the delay laws and the apodization of an array. Such simulation is implemented in this work, using a model that calculates the acoustic pressure in a space point. The approach uses the convolution integral and the spatial impulsive response methods. This computational solution is exact and relatively simple. That does not usually happen to other methods with a higher computational time. The acoustic field simulations obtained with the model implemented in Matlab are verified experimentally. Measurements of the pressure field generated by rectangular transducers in 400 kHz to 2.2 MHz and by an 1 MHz array were made in an immersion tank, using a punctual hidrophone and a computerized system for acoustic field measurements. The comparison between the simulated and experimental results shows good agreement.