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Caractérisation et modélisation d'un micro-capteur magnétoélectrique / Characterization and Modeling of Magnetoelectric Micro SensorsNguyen, Thi Ngoc 06 July 2018 (has links)
Les capteurs magnéto-électrique (ME) sont une alternative prometteuse pour mesurer de faibles signaux magnétiques. Précédemment le choix était généralement de déposer des couches minces magnétostrictives sur un matériau piézoélectrique massif conduisant à des systèmes macroscopiques de taille milllimétrique. L’intégration de ces systèmes dans des MEMS (micro-electro-mechanical systems) requiertà la fois de résoudre les problèmes d’intégration de matériaux actif sur silicium, et de mesurer des petits signaux étant donné l’importante réduction de la réponse du système lorsqu’il est miniaturisé.Dans cette optique, le premier objectif de ce travail de thèse a été d’intégrer un matériau piézoélectrique sur un substrat de silicium tout en conservant une excellente qualité cristalline. Pb(Zr ₀ , ₅ ₂Ti ₀ ,₄₈)O₃ (PZT) a été retenu pour ces excellente propriétés piézoélectriques. L’intégration de la couche mince ce fait sur silicium qui est le substrat de prédilection pour la fabrication de microsystèmes avec les procédés microélectroniques standards. La qualité cristalline des matériaux actifs est directement corrélée aux couches d'adaptation utilisées pour obtenir une bonne qualité cristalline sur silicium. Pour cel l'intégration d'une tricouche composée de zircone stabilisée à l'yttrium (YSZ), d'oxyde de cérium (CeO₂) et de SrTiO₃ permet ensuitela croissance des pérovskites d'intérêt pour le dispositif. Le choix de l’électrode conductrice inférieure (SrRuO₃ ou La ₀ ,₆₆Sr₀₃₃MnO₃ dans le cas présent) permet de contrôler l’orientation de la maille de PZT.Une première étude des propriétés piézoélectriques de la couche mince de PZT sous la forme d’une poutre libre pour son intégration dans un système magnétoélectrique a été réalisé. La mesure de la déformation de la poutre induite par l'application d'une tension électrique permet d'extraire un coefficient d₃₁ de -53pmV⁻¹, valeur inférieure au matériau massif mais à l'état de l'art dans ce type de dispositif. Dans une seconde étape, l’utilisation de la poutre comme résonateur à été étudiée. L’étude dynamique du système a permis d'obtenir la fréquence de résonance et le facteur de qualité. Le déplacement de la fréquence caractéristique du système en fonction d'une contrainte induite par une tension DC a été investigué. Enfin, l'ajout d'une couche de matériau magnétostrictif (TbFeCo) sur la poutre a finalisé la structure du capteur. Le capteur ainsi obtenu a été caractérisé et une sensibilité d’une dizaine de micro Tesla a été obtenue. / Magneto-electric (ME) sensors have been demonstrated as a promising alternative for the detection of weak magnetic signals with high sensitivity. To date, most applications focused on the use of bulk piezoelectric materials on which magnetostrictive thin films are deposited leading to millimeter-sized devices. The integration of such devices into micro-electro-mechanical systems (MEMS), bringing smaller size and lower power consumption, involves addressing several scientific issues ranging from the integration of active materials on silicon to the strong reduction in amplitude of generated signals related to the size reduction of the sensor.In this context, the first goal of this thesis work was to integrate high crystalline quality piezoelectric thin films on silicon.Pb(Zr ₓTi ₁ ₋₁)O₃ (PZT) with a morphotropic composition (x=0.52) having high electromechanical coupling factor was chosen. Silicon is a necessary template as it allows for the use of conventional clean room processes for the realization of the microsystem. The crystalline quality of the active films is directly linked to the buffer layers that promote the crystalline growth on silicon. For this purpose, Yttria-stabilized Zirconia (YSZ) was used in combination with CeO₂ and SrTiO₃ to allow further growth of epitaxial perovskites. The choice of the bottom electrode material (SrRuO₃ or La ₀ ,₆₆Sr₀₃₃MnO₃ in this work) further tunes the crystalline orientation of the PZT layer.To probe the potential of such PZT thin films for ME devices, the first step was to characterize the electromechanical properties of this material in a free standing cantilever structure. Under an applied electric field, the measured displacement of the epitaxial PZT-based cantilevers is characterized by a coefficient d₃₁ =-53pmV⁻¹ , a reduced value with respect to the bulk material but that can be enhanced by further optimizing the film growth. The second step consists in ascertaining the ability of the cantilever to be used as resonator. For that purpose, first characterizations of oscillators have been performed to extract the resonant frequencies and the associated quality factors. Then, the resonant frequency shift with DC bias-induced stress was measured. Finally, a magnetostrictive layer of TbFeCo was added on the PZT cantilevers to sense magnetic field based on the ME effect. The resulting resonant frequency shift with external applied magnetic field was characterized with a typical sensitivity of 10’s of µT.
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Magnetic tunnel junctions for ultrasensitive all-oxide hybrid sensors for medical applications / Jonctions tunnel magnétiques pour capteurs hybrides tout-oxydes ultrasensibles pour des applications médicalesKurij, Georg 24 March 2016 (has links)
La détection des très faibles valeurs de champ magnétique est un enjeu important pour l’émergence à plus grande échelle de techniques pour le domaine du médical telles que la magnéto cardiographie, ou la magnétoencéphalographie. Les solutions existantes industrialisées reposent sur l’utilisation de jonctions tunnels supraconductrices qui permettent de fabriques des SQUIDS (Superconducting Quantum Intereference Device) qui sont les briques de base des magnétomètres avec des sensibilités de l’ordre de la dizaine de femtotesla. Cependant cette approche impose de travailler à des températures très basses qui ne sont accessibles qu’avec de l’hélium liquide. Un approche récente, développée par le Spec-CEA permet de travailler à l’azote liquide (77K) ce qui lève un certain nombre de contraintes. Le dispositif est un capteur mixte composé d’une boucle supraconductrice de grande taille qui contient une constriction de taille micrométrique sur laquelle est rapportée une magnétorésistance tunnel qui sert de sonde locale du champ magnétique. L’objectif du travail dans ce travail de thèse est de poursuivre le développement de ce type de capteur en utilisant visant des structures tout oxyde. En effet l’intégration complète de ce type de capteur permettrait de gagner encore en termes de performances et d’atteindre une résolution de l’ordre du femtotesla. Pour ce faire le travail vise à intégrer une jonction tunnel tout oxyde directement par épitaxie sur la constriction. La jonction tunnel sera réalisée à partie d’oxydes magnétiques tels que les composés LaSrMnO3 ou SrRuO3 qui sont deux matériaux ferromagnétiques à la température de l’azote liquide. / Sensing of extremely weak magnetic signals, such as produced by electrical activity of the human heart and brain, still remains a challenge. A very promising alternative to established field-sensing techniques is a novel, spin electronic based, ultrasensitive device called an all-oxide mixed sensor. It is formed by a superconducting loop, acting as a flux-to-field transformer and field amplifier, combined with a magnetic tunnel junction sensing the field.Our research activities have the goal to improve the performance of the mixed sensor, focusing on its core component – the magnetic tunnel junction (MTJ). The capability of an MTJ is predominantly determined by the quality of the tunnel barrier and by the stability of magnetization states. In this context, oxide materials, known for their remarkable physical properties, have already shown their advantages. Thus, studies on La0.7Sr0.3MnO3/SrTi0.8Nb0.2O3 functional oxide interfaces, exploration of SrRuO3/ La0.7Sr0.3MnO3 exchange bias system, and the final integration of these two components into a magnetic tunnel junction form the main part of our work.In the presented thesis, oxide thin films and heterostructures used for studies were grown by pulsed laser deposition (PLD). We fabricated electronic devices for investigations using clean room microfabrication techniques , e.g. optical lithography, chemically assisted ion beam etching (CAIBE) and sputtering. Temperature dependent magnetic and (magneto-) transport measurements were performed.Metal-semiconductor interfaces formed by the half-metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) and heavily doped semiconductor SrTi0.8Nb0.2O3 (Nb:STO) were studied. Antiferromagnetic coupling at the interface of the LaSrMnO3 and itinerant ferromagnet SrRuO3 was explored. Magnetic tunnel junctions with Schottky barrier were investigated (MTJs with Nb:STO and LSMRO).
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Shape-Controlled Flexible Microelectronics Facilitated by Integrated Sensors and Conductive Polymer ActuatorsRivkin, Boris, Becker, Christian, Akbar, Farzin, Ravishankar, Rachappa, Karnaushenko, Dmitriy D., Naumann, Ronald, Mirhajivarzaneh, Alaleh, Medina-Sánchez, Mariana, Karnaushenko, Daniil, Schmidt, Oliver G. 22 July 2022 (has links)
The next generation of biomedical tools requires reshapeable electronics to closely interface with biological tissues. This will offer unique mechanical properties and the ability to conform to irregular geometries while being robust and lightweight. Such devices can be achieved with soft materials and thin-film structures that are able to reshape on demand. However, reshaping at the submillimeter scale remains a challenging task. Herein, shape-controlled microscale devices are demonstrated that integrate electronic sensors and electroactive polymer actuators. The fast and biocompatible actuators are capable of actively reshaping the device into flat or curved geometries. The curvature and position of the devices are monitored with strain or magnetic sensors. The sensor signals are used in a closed feedback loop to control the actuators. The devices are wafer-scale microfabricated resulting in multiple functional units capable of grasping, holding, and releasing biological tissues, as demonstrated with a neuronal bundle.
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[en] GEOMETRIC MAGNETIC DISCRIMINATOR SENSOR FOR SMART PIGS / [pt] SENSOR GEOMÉTRICO MAGNÉTICO DISCRIMINADOR PARA PIGS INSTRUMENTADOSVINICIUS DE CARVALHO LIMA 05 January 2005 (has links)
[pt] Este trabalho apresenta o desenvolvimento de um sensor
inovador combinando três técnicas de inspeção utilizadas
nos Pigs Instrumentados Geométrico e Magnético, para a
detecção e caracterização de defeitos na geometria em
tubulações de aço. O sensor GMD, Geométrico Magnético
Discriminador, faz a leitura magnética do duto através da
técnica de campo de fuga magnético, com a adição da leitura
geométrica além da discriminação de defeitos internos de
externos. A combinação dessas três tecnologias habilita a
construção de uma ferramenta de inspeção de alta resolução
compacta e capaz de identificar e quantificar, com apenas
uma coroa de sensores, amassamentos, perdas de espessura e
além da sua combinação. Este estudo se apresenta em um
momento oportuno, já que a Integração de dados é o ponto
fundamental da recente norma de gerenciamento de ricos em
dutos, API 1160, na qual combinando os resultados das
inspeções de geometria e corrosão, tem-se uma melhor
avaliação de risco. Testes foram realizados utilizando um
PIG Plano com corpos de prova contendo defeitos variados.
Os resultados verificaram que o sensor GMD quantifica e
discrimina amassamentos com perda de espessura. Aspectos
técnicos do desenvolvimento como os detalhes construtivos
do sensor, testes de avaliação a resultados de laboratório
são apresentados. / [en] This thesis presents the development of an innovative
sensor head for detection and characterization of geometric
defects in steel pipes that combines three inspection
techniques usually employed separately in Caliper and
Magnetic Flux Leakage (MFL) PIGs. The novel Geometric
Magnetic Discriminator (GMD) sensor performs high-
resolution magnetic pipeline readings using MFL with the
addition of internal pipe geometry evaluations and
discrimination between internal and external defects. The
combination of these technologies in a single sensor
facilitates characterization of dents and corrosions, while
at the same time optimizing the PIG set-up. According to
the repair criteria in the standard API1160, combined
defects such as a dent with metal loss, which in the past
could only be detected through combined data of two
different runs (MFL+ Caliper), must be repaired
immediately. The GMD sensor was tested in a linear
test rig, known as Flat Pig, and data were taken from
different defect sets. Evaluation tests demonstrated that
the GMD sensor sizes and discriminates a dent with metal
loss. Technical aspects of the development, e.g.: the
construction details of the sensor, evaluation tests and
laboratory results are presented.
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Fusion de données inertielles et magnétiques pour l’estimation de l’attitude sous contrainte énergétique d’un corps rigide accéléré / Inertial and magnetic data fusion for attitude estimation under energetic constraint for accelerated rigid bodyMakni, Aida 29 March 2016 (has links)
Dans ce travail de thèse on s’intéresse à l’estimation de l’attitude d’un corps rigideen mouvement dans l’espace 3D en utilisant les quaternions comme représentation. Cetteproblématique a été largement étudiée dans la littérature sous divers domaines d’application.L’objectif de la thèse est de proposer de nouvelles méthodes de fusion de données en combinantdes mesures inertielles et magnétiques. Dans un premier temps, nous nous sommesintéressés à l’estimation de l’attitude en cas de mouvement accéléré où l’accélération linéairedu corps n’est plus négligeable devant la gravité. Deux approches ont été proposées dans cecadre. La première utilise un filtre de Kalman adaptatif pour la compensation des accélérationslinéaires. Précisément, des lois de détection ont été développées pour distinguer d’unefaçon automatique les différentes phases de mouvement (statiques et dynamiques). Ainsi, lamatrice de covariance associée à l’accélération linéaire est estimée afin d’ajuster le gain dufiltre. La deuxième approche consiste à intégrer un filtre singulier élaboré sur la base d’unnouveau modèle, dans lequel le modèle du processus est défini en se basant sur les mesuresissues de l’accéléromètre tandis que le modèle d’observation est défini par les mesures issuesdu gyromètres et du magnétomètres. Cette formulation permet de prendre en compte l’effetdes accélérations linéaires d’une manière efficace. Dans un deuxième temps, on s’est focalisésur l’estimation de l’attitude avec utilisation intermittente de gyromètres, considérés commecapteurs énergivores. Nous avons étudié dans ce cas la façon la plus adéquate afin de réduirel’acquisition des mesures de vitesse angulaire tout en gardant une qualité acceptable de l’estimationde l’attitude. Toutes les approches développées ont été validées par des simulationsnumériques ainsi que des expérimentations utilisant des données réelles. / In this PhD. thesis we deal with attitude estimation of accelerated rigid body moving in the 3D space using quaternion parameterization. This problem has been widely studied in the literature in various application areas. The main objective of the thesis is to propose new methods for data fusion to combine inertial gyros) and magnetic measurements. The first challenge concerns the attitude estimation during dynamic cases, in which external acceleration of the body is not negligible compared to the Gravity. Two main approaches are proposed in this context. Firstly, a quatenion-based adaptive Kalman filter (q-AKF) was designed in order to compensate for such external acceleration. Precisely, a smart detector is designed to decide whether the body is in static or dynamic case. Then, the covariance matrix of the external acceleration is estimated to tune the filter gain. Second, we developed descriptor filter based on a new formulation of the dynamic model where the process model is fed by accelerometer measurements while observation model is fed by gyros and magnetometer measurements. Such modeling gives rise to a descriptor system. The resulting model allows taking the external acceleration of the body into account in a very efficient way. The second challenge is related to the energy consumption issue of gyroscope, considered as the most power consuming sensor. We study the way to reduce the gyro measurements acquisition by switching on/off the sensor while maintaining an acceptable attitude estimation. The effciency of the proposed methods is evaluated by means of numerical simulations and experimental tests.
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[en] HIGH SENSITIVITY GMI MAGNETOMETER FOR THE MEASUREMENT OF ULTRA-WEAK MAGNETIC FIELDS / [pt] MAGNETÔMETRO GMI DE ALTA SENSIBILIDADE PARA MEDIÇÃO DE CAMPOS MAGNÉTICOS ULTRA-FRACOSEDUARDO COSTA DA SILVA 18 July 2018 (has links)
[pt] Esta Tese teve por objetivo desenvolver um magnetômetro de alta sensibilidade, baseado nas características de fase do efeito da Magnetoimpedância Gigante (GMI – Giant Magnetoimpedance), para medição de campos magnéticos ultra-fracos. Elementos sensores GMI apresentam grande potencial na fabricação de magnetômetros que conciliem alta sensibilidade e elevada resolução espacial
com baixo custo. A otimização da sensibilidade do transdutor magnético é diretamente afetada pela sensibilidade de seus elementos sensores GMI, cuja maximização é um processo intrinsecamente multivariável. Consequentemente, a metodologia experimental empregada iniciou-se pelo desenvolvimento de um sistema automático de caracterização das amostras GMI, de modo a se garantir a agilidade do processo de caracterização, possibilitando a obtenção de um volume significativo de informações experimentais. A análise minuciosa dos dados provenientes das medições experimentais permitiu a definição do ponto ótimo de operação das amostras GMI estudadas. Em todas as medições experimentais
realizadas foram obtidas e avaliadas as curvas de histerese das amostras GMI. Na sequência, foram idealizados circuitos eletrônicos para condicionamento das amostras GMI e leitura das características de fase de sua impedância, destacandose a configuração eletrônica desenvolvida para a amplificação da sensibilidade de fase. Foram, inclusive, depositadas patentes nacionais e internacionais referentes
ao método proposto e ao novo transdutor magnético GMI (PI 0902770-0; PI 1004686-0; WO/2010/094096 e WO/2012/048395). As caracterizações e ensaios experimentais realizados indicaram a eficácia da abordagem proposta, evidenciando o grande potencial do magnetômetro GMI desenvolvido, o qual
apresentou uma elevada sensibilidade de 5 mV/nT. A resolução do magnetômetro foi limitada pelo ruído magnético ambiental, indicando que sua capacidade de medição de campos inferiores aos níveis de ruído poderá ser claramente evidenciada quando for avaliada em ambiente magneticamente blindado. Os estudos teórico-experimentais realizados indicam o potencial do transdutor magnético GMI desenvolvido, caracterizado por seu baixo custo e elevada sensibilidade, para aplicação na medição de campos magnéticos ultra-fracos. / [en] This Thesis aimed at developing a high sensitivity magnetometer, based on the phase characteristics of the Giant Magnetoimpedance effect (GMI), for measuring ultra-weak magnetic fields. GMI sensor elements have great potential to implement magnetometers that combine high sensitivity and high spatial resolution with low cost. The optimization of the magnetic transducer sensitivity is directly affected by the sensitivity of its GMI sensor elements, whose maximization is inherently multivariate. Consequently, the first step of the experimental methodology employed was to develop an automatic system for the characterization of GMI samples, so as to ensure the agility of the characterization process, allowing the gathering of a significant amount of experimental data. A thorough analysis of the experimental data led to the definition of the optimal operation point of the analyzed GMI samples. The hysteresis curves of the GMI
samples were obtained and evaluated, in all of the performed experimental measurements. Based on the characterization studies results, electronic circuits were designed for conditioning the GMI samples and reading their impedance phase characteristics, highlighting the new electronic configuration developed for
enhancing the phase sensitivity. National and international patents were filed, related to the proposed method, for sensitivity enhancement, and to the new GMI magnetometer (PI 0902770-0; PI 1004686-0; WO/2010/094096 e WO/2012/048395). The performed experimental characterizations and assays
indicated the effectiveness of the proposed approach, showing the great potential of the developed GMI magnetometer, which presents a high sensitivity of 5 mV/nT. The magnetometer resolution was limited by the environmental magnetic noise, pointing out their capability in measuring fields below the environmental noise level, which can be clearly evidenced only when evaluated in a magnetically shielded room. The theoretical and experimental studies carried out indicate the potential of the developed GMI magnetic transducer, characterized by its low cost and high sensitivity, for applications involving the measurement of
ultra-weak magnetic fields.
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[en] METHODS TO HOMOGENIZE THE IMPEDANCE PHASE CHARACTERISTICS OF GMI SENSORS / [pt] MÉTODOS PARA HOMOGENEIZAÇÃO DAS CARACTERÍSTICAS DE FASE DA IMPEDÂNCIA DE SENSORES GMI19 November 2021 (has links)
[pt] A utilização de magnetômetros possibilita o diagnóstico não invasivo e inócuo das variáveis fisiológicas já mensuradas pelos procedimentos padrão e oferece informações complementares sobre outras variáveis fisiológicas. Fontes biológicas geram densidades de fluxo magnético com ordem de grandeza entre 1 nT e 1 fT, com frequências até 1 kHz. Essas grandezas são ínfimas quando comparadas com a gerada pelo planeta, que é da ordem de 20 uT e está onipresente na atmosfera. Portanto, para mensurar campos biomagnéticos, é necessário atenuar essa interferência eletromagnética, sendo empregadas câmaras magneticamente blindadas e/ou transdutores em configuração gradiométrica. As câmaras blindadas apresentam alto desempenho de filtragem, mas têm elevado custo e pouca praticidade. Uma configuração gradiométrica utiliza uma leitura diferencial de dois ou mais elementos sensores idênticos, melhorando significativamente a relação sinal/ruído com baixo custo de implementação. Seu funcionamento se baseia na premissa de que os sensores têm comportamento idêntico. No entanto, foi observado que as fitas GMI, mesmo apresentando a mesma composição química e mesmas dimensões físicas, não apresentam as mesmas variações de fase para uma mesma variação do campo magnético. Ou seja, foi constatado um comportamento heterogêneo das amostras, o que impossibilitaria o desenvolvimento de um gradiômetro baseado nesses sensores. Diante deste impedimento, foi considerado o desenvolvimento de um circuito capaz de homogeneizar as variações de impedância entre duas amostras, quando associado a uma delas. Assim, a presente dissertação apresenta três métodos para a homogeneização das características de fase de amostras GMI e identifica o mais adequado para aplicações biomédicas. / [en] The use of magnetometers enables noninvasive and innocuous physiological variables already measured by standard procedures, and in certain cases, such as the Magnetocardiography offers additional information on other physiological variables diagnosis. Typically, the human heart generates a magnetic field with flux magnitude and frequency of 1 nT to 1 kHz. These quantities are minuscule compared with Earth s magnetic field, which is of the order of 20 uT and is omnipresent in the atmosphere. Therefore, to measure biomagnetic fields, it is necessary to reduce this and other electromagnetic interference, magnetically shielded cameras and transducers in gradiometric configuration are commonly used. Shielded cameras feature high performance filter, but have high cost and little practicality. A gradiometric configuration uses a differential reading of two or more identical sensor elements, significantly improving the signal/noise ratio with low implementation cost. However, its operation based on the premise that the sensors have identical behavior. Unfortunately, it was found that GMI ribbons, despite having the same chemical composition and same physical dimensions does not present the same phase variations for the same variation in magnetic field. That is, a heterogeneous behavior of the samples, which would prevent the development of a gradiometer based on these sensors. Given this impairment, it was considered developing a circuit capable of homogenizing the variations in impedance between two samples when associated with them. Thus, this paper presents three distinct characteristics of the homogenization phase samples GMI methods and identifies the most suitable for biomedical applications through a comparative analysis of the performance of the methods.
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Design and Implementation of Real-Time Software for Sourceless Full Body-Tracking using Small Inertial/Magnetic SensorsMontgomery, Eric W. 25 April 2003 (has links)
No description available.
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[pt] DESENVOLVIMENTO DE UM SISTEMA AUTOMATIZADO, BASEADO NO CONCEITO DE HARDWARE EVOLUCIONÁRIO, PARA DETERMINAÇÃO DO PONTO ÓTIMO DE OPERAÇÃO DE SENSORES GMI / [en] DEVELOPMENT OF AN AUTOMATED SYSTEM, BASED ON THE CONCEPT OF EVOLUTIONARY HARDWARE, AIMED AT DETERMINING THE OPTIMAL OPERATING POINT OF GMI SENSORSJAIRO DANIEL BENAVIDES MORA 14 November 2017 (has links)
[pt] Elementos sensores baseados no efeito GMI são uma nova família de sensores magnéticos que apresentam grande quando submetidos a campos magnéticos externos. Estes sensores têm sido utilizados no desenvolvimento de magnetômetros de alta sensibilidade, destinados à medição de campos ultra fracos. Por sua vez, a sensibilidade de um magnetômetro está diretamente associada à sensibilidade de seus elementos sensores. No caso de amostras GMI, esta sensibilidade é otimizada buscando-se a maximização da variação do módulo ou da fase da impedância em função do campo magnético ao qual a amostra é submetida. Estudos recentes mostram que transdutores GMI baseados na variação de fase podem exibir sensibilidades até 100 vezes superiores às apresentadas por transdutores baseados na leitura do módulo do elemento sensor, o que fez com que os trabalhos conduzidos nesta dissertação focassem na maximização da sensibilidade de fase, a qual é majoritariamente dependente de quatro fatores: o comprimento da amostra, o campo magnético externo, o nível DC e a frequência da corrente de excitação. Contudo, a busca do conjunto de parâmetros que otimiza a sensibilidade das amostras é geralmente empírica e muito demorada. Esta dissertação propõe uma nova técnica de otimização da sensibilidade, baseada no uso de algoritmos genéticos evoluindo em hardware, a fim de se definir qual o conjunto de parâmetros responsável pela maximização da sensibilidade das amostras. Ressalta-se que, além dos parâmetros de otimização anteriormente explicitados, também foram realizados testes considerando a amplitude da corrente de excitação como uma variável livre, sendo que os resultados obtidos são apresentados e discutidos. Foi implementada uma bancada de testes e desenvolvida uma interface gráfica em LabVIEW, para monitorar e medir o comportamento da impedância de amostras GMI em função de variações nos parâmetros de interesse. Por sua vez, implementou-se um módulo de otimização em Matlab, baseado em algoritmos genéticos, responsável por encontrar a combinação de parâmetros que maximiza a sensibilidade dos sensores GMI avaliados (ponto ótimo de operação). / [en] GMI sensors are a new family of magnetic sensors that exhibit a huge variation of their impedance when subjected to external magnetic fields. These sensors have been used in the development of high sensitivity magnetometers, aimed at measuring ultra-weak magnetic fields. In turn, the sensitivity of a magnetometer is directly associated with the sensitivity of their sensor elements. In the case of GMI samples, this sensitivity is optimized by maximizing the variation of the impedance magnitude or phase as a function of the magnetic field applied to the sample. Recent studies show that GMI transducers based on phase variation can exhibit sensitivities up to 100 times higher than those presented by transducers based on impedance magnitude readings. The results obtained in these previous studies made the current work focusing on the maximization of phase sensitivity, which is mostly dependent on four factors: sample length, external magnetic field, DC level and frequency of the excitation current. However, the search for the set of parameters that optimizes the sensitivity of the samples is usually empirical and very time consuming. Thus, this dissertation proposes a new optimization technique, based on the use of genetic algorithms evolving on hardware, in order to define which set of parameters is responsible for maximizing the sensitivity of the samples. It should be noted that in addition to the optimization parameters previously described, this work also carried out tests considering the amplitude of the excitation current as a free variable, and the results obtained are presented and discussed. A test bench was implemented and a graphical interface was developed in LabVIEW to monitor and measure the impedance behavior of GMI samples due to variations in the parameters of interest. In turn, a Matlab optimization module based on genetic algorithms was implemented, in order to find the combination of parameters that maximizes the impedance phase sensitivity of the evaluated GMI sensors (optimum operating point).
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Integrated Micro-Origami SensoricsBecker, Christian 16 May 2024 (has links)
This work presents the successful development of micro-origami sensorics by 3D self-assembling and reconfiguring in space integrated thin-film magnetic sensors, which rely on anisotropic (AMR) and giant magnetoresistance (GMR). Stimuli responsive polymeric materials able to reshape into mesoscale 3D “Swiss-roll” and polygonal architectures accomplish a strain driven parallel spatial realignment of magnetic sensors from the in-plane state. High performance 3D magnetic vector angular encoders demonstrates the successful realization of complex sensor configurations. The proposed concepts rely on parallel wafer scale processes, which allow for a monolithic fabrication of 3D sensor arrays and pave the way towards active sensory matrix circuits.
As a proof of this concept, magneto-resistive Wheatstone bridge sensors are developed and integrated in the self-assembling platform at predefined rigid regions and integrated with an active matrix backplane circuit. This circuit, based on a-IGZO TFT technology, is specially designed for the operation with the Wheatstone bridge differential sensors and optimized to be compatible with the micro-origami self-folding technology. Such an active sensory matrix system with integrated 3D self-assembled pixels is called Integrated Micro-Origami Sensors or in short IMOS. IMOS is capable for static and dynamic mapping of magnetic fields enabling spatiotemporal mapping of artificial magnetic hair arrays embedded in an elastic skin layer. The presented results offer a fresh strategy for large area integration of microscale 3D electronic devices with various vector functionalities in active matrix circuits, which are of great interest in novel robotics, bioelectronics and diagnostic systems.
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