La science a avancé depuis le XIX ème siècle. Des nouveaux outils sont apparus : la microscopie optique nous donne la vision des cellules, la microscopie électronique nous entraine au cœur de celles-ci. L’imagerie par résonance magnétique est apparue dans les années soixante-dix. Depuis son évolution, l’IRM nous entraine de plus en plus loin dans les profondeurs secrètes de nos cerveaux. La possibilité d’observer l’activité neuronale à l’aide de l’imagerie fonctionnelle est une grande révolution. Cette thèse montrera la possibilité que l’on a d’observer l’activité d’un neurone individuel sans modification de son réseau grâce à l’imagerie rehaussée au manganèse. L’étude sera effectuée sur des Aplysies à très haut champ (17T). Ces animaux sont des mollusques marins gastropodes qui possèdent une particularité : leurs neurones sont de tailles importantes, ils peuvent atteindre 1 mm de diamètre. Leurs neurones sont regroupés en plusieurs ganglions. Mon étude portera sur le ganglion buccal, qui est le ganglion le plus étudié dans les recherches en électrophysiologie. Avant de réaliser les acquisitions, j’ai dû concevoir plusieurs antennes de tailles microscopiques adaptées à la taille des ganglions. En réduisant la taille des antennes, le rapport signal sur bruit augmente. Dans un deuxième temps, une double antenne a été développée permettant l’acquisition de deux échantillons simultanément. Cette antenne a nécessité de créer des préamplificateurs fonctionnant à 730 MHz. La première série d’expériences a permis d’observer l’évolution de l’activité neuronale selon différents stimulus liés au comportement alimentaire des aplysies in-vivo. J’ai montré grâce à la technique mise en place que l’on peut distinguer par IRM l’activité de chaque neurone face à un stimulus. Par la suite, pour continuer ce travail, une deuxième série d’expériences a été effectuée in-vitro. J’ai étudié le comportement des neurones selon les neuro-stimulateurs perfusés : la dopamine et la sérotonine, tous les deux présents naturellement dans l’aplysie. Globalement les neurones ont été activés mais après les avoir observés individuellement, j’ai remarqué quelques différences selon les neurotransmetteurs. Cette technique peut maintenant être utilisée pour étudier d’autres conduites de l’aplysie comme le comportement compulsif. L’étude sur la mémoire peut être aussi envisagée. Les origines comportementales ont probablement des mécanismes identiques entre les différentes espèces animales et donc avec l’Homme comme l’a démontré les études d’Eric Kandel sur la mémoire. / Science has evolved since the 19th century. New tools have appeared such as optical microscopy which gives us the vision of cells and electronic microscopy which leads us into their hearts. The magnetic resonance imaging appeared in the seventies. Evolving over time, the MRI has taken us farther and farther into the secret depths of our brains. The possibility of observing the neuronal activity thanks to the functional imaging is a major evolution. This thesis will show the possibility we have to observe the activity of a single neuron without modification of its network thanks to the manganese enhanced magnetic resonance imaging technique. The study was done on the Aplysia at very high field magnet (17T). These animals are marine gastropod mollusks with a peculiarity: their neurons are of important size and can reach 1 mm in diameter. Their neurons are grouped into several ganglia. My study concerns the buccal ganglion which is the most studied ganglia in the research in electrophysiology. Before making any acquisitions, I had to conceive several microscopic coils adapted to the size of the ganglions. By reducing the size of the coils, the signal of the noise ratio increases. Then, a double coil allowing the simultaneous acquisition of two samples was built. This antenna required the construction of pre-amplifiers operating at 730 MHz. The first series of experiments helped observe the evolution of the neuronal activity according to different stimuli linked to the eating habits of the Aplysia in vivo. Thanks to the technique implemented, I shall show that, using MRI, it is possible to distinguish the activity of each neuron with respect to a stimulus. Afterwards, to continue this work, a second series of experiments was made in vitro. I studied the behavior of neurons when perfused with neural stimulators: dopamine and serotonin, both naturally present in the Aplysia. Generally, all neurons were activated but when observing them individually, I noticed some differences. Studies in electrophysiology will allow us to get a better understanding and a confirmation of the results of this study. The MEMRI technique can be used in the future to study various disorders such as compulsive behaviors, which are present in the Aplysia, and probably have the same origins as in humans, given that many fundamental processes (such as memory studied by Eric Kandel who he demonstrated that human and Aplysia memories works with the same mechanism) are similar between the two species.

A reflectometria no domínio do tempo permite estimar o teor de umidade de um meio através da sua correlação com a constante dielétrica. Uma sonda helicoidal TDR, que pode ser cravada em conjunto outros ensaios de penetração in situ para a estimativa do teor de umidade em diversas profundidades, tem aplicação interessante para a investigação geotécnica do subsolo. No presente trabalho, uma sonda TDR foi adaptada e utilizada em conjunto ao ensaio CPT para caracterização de um perfil de solo arenoso não saturado que ocorre na região de Bauru (SP). A calibração dessa sonda foi feita em laboratório especificamente para esse solo. As equações de calibração que mostraram os melhores resultados foram definidas correlacionando a constante dielétrica, condutividade elétrica aparente e a massa específica seca com o teor de umidade. Com o intuito de melhorar a acurácia na determinação do teor de umidade em campo e eliminar possíveis interferências no registro da onda eletromagnética, foram efetuadas modificações em algumas características do projeto original dessa sonda. Tais modificações consistiram em separar os eletrodos condutores e as partes metálicas da sonda, e eliminar o cabo coaxial de extensão, conectando a sonda diretamente a um cabo coaxial de 12 m de comprimento. Tais mudanças levaram a uma melhoria significativa na determinação do perfil de teor de umidade do local estudado. Os valores de teor de umidade de campo determinados usando o TDR ao longo de 8 m de profundidade foram comparados com os valores de referência obtidos de amostras deformadas retiradas com trado mecânico. O erro médio na estimativa do perfil de teor de umidade gravimétrico utilizando a sonda TDR helicoidal foi de 1.61%, na última campanha de ensaios realizados. Os resultados dessa pesquisa indicam que esta ferramenta é adequada para estimar do perfil de teor de umidade para uso em conjunto com o ensaio CPT. / The time domain reflectometry allows estimating the moisture content of a medium by means of its correlation with the dielectric constant. A coil TDR probe, which can be driven into the ground together with others in situ penetration tests, can be used to estimate the moisture content at different depths. It is an interesting approach for geotechnical site characterization. In this work, a coil TDR probe was adapted and used in combination with the CPT test for the site characterization of an unsaturated sandy soil profile which occurs in the region of Bauru (SP). The probe calibration was performed in laboratory specifically for that soil. The calibration equation, which presented the best results, were defined correlating the dielectric constant, electrical conductivity and dry density with the moisture content. In order to improve the accuracy for determining the water content in the field and to eliminate possible interference on the electromagnetic wave registration, modifications were made in some characteristics of the original design of this probe. Such modifications consisted in separating the conductive electrodes from the metal parts of the probe, and eliminating the coaxial extension cable, connecting the probe directly to a coaxial cable 12 m long. Such changes have led to a significant improvement in the determination of the moisture content profile of the studied site. The moisture content values determined in situ by using the TDR along 8 m depth were compared with reference values obtained from disturbed soil samples collected using mechanical augers. The root mean square error of the gravimetric water content profile using the TDR coil probe was 1.61% in the last test campaign. The results of this research indicate that this tool is suitable to estimate the gravimetric moisture content together with the CPT test.

Die vorliegende Arbeit beschreibt das Verhalten von Polypeptid-Blockcopolymeren in der festen Phase und in selektiven Lösungsmitteln. Blockcopolymere auf Basis von Poly(L-glutaminsäure-5-benzylester) (PBLGlu) oder Poly(Nε-benzoyloxycarbonyl-L-lysin) (PZLLys), die in dieser Arbeit eingesetzt wurden, besitzen wegen ihrer helikalen Sekundärstruktur eine sog. Stäbchen-Knäuel-Geometrie, wobei die Knäuelkomponente Polystyrol oder Polybutadien ist. Die Phasenbildung dieser Blockcopolymere ist durch die Packungseigenschaften des rigiden Blocks beeinflusst. Es wurden bevorzugt lamellare Strukturen gebildet, in denen die Stäbchen parallel angeordnet sind. Das Vorhandensein eines permanenten Dipolmomentes führt zur Wechselwirkung zwischen den Helices und zur Erhöhung des Ordnungsgrades in der Phase. Ein zusätzlicher Parameter, der die Morphologie der Phase beeinflußt, ist die Chiralität der Peptidhelix, durch die chirale Überstrukturen induziert werden. In dünnen Filmen (40 nm), wo die Geometrie begrenzt ist, führt es zu Frustrationen in der Phase. Die dadurch entstandene Spannung wurde durch einen zick-zack-artigen Lamellenverlauf abgebaut. In selektiven Lösungsmitteln für die synthetische Komponente (PS) bilden die Polypeptid-Blockcopolymere vesikuläre Strukturen, deren kugel- oder wurmförmige Geometrie von der Elastizität der Membran abhängig ist. Durch Entfernung der Z-Schutzgruppe kann PZLLys in eine wasserlösliche Form überführt werden, so dass die PB-PLLys Blockcopolymere unter Bildung von Vesikeln in Wasser löslich sind. Dabei ist die Konformation des Peptids vom pH-Wert des Mediums abhängig und kann von einem Knäuel zu einer Helix reversibel geschaltet werden. Beim Modifizieren der Sekundärstruktur wurde eine Änderung der Aggregationszahl beobachtet. Somit können diese Blockcopolymere für die Herstellung von schaltbaren Aggregaten eingesetzt werden. / The presented work describes the behaviour of polypeptide-blockcopolymers in the solid-state and well as in selective solvents. Blockcopolymers consisting of PBLGlu or PZLLys / which have been utilized in this work, possess, because of their helical structure, a so-called Rod-Coil Geometry, where the coil component consists of polystyrene or polybutadiene. The phase morphology of these block copolymers is dominated by the packing properties of the rigid blocks. Most commonly, lamellar structures were formed, where the rods were ordered in a parallel fashion. The presence of a permanent dipole moment leads to an interaction between the helices and to an increase in the degree of order within the phase. An additional parameter that influences the phase morphology is the chirality of the peptide helix, which induces the formation of chiral superstructures. In thin films (40 nm), where the geometry is limited, a disordering within the phase is observed. The resulting tension leads to the formation of a zig-zag lamellar pattern. In selective solvents of the synthetic component (PS) of the blockcopolymer, formation of vesicular structures are observed, with spherical or worm-like geometry, depending on the elasticity of the membrane. Through removal of the z-protective groups, PZLLys becomes soluble in water, through the formation of PB-PLLys blockcopolymer vesicles. The conformation of the peptide is dependent on the pH value of the medium and can be reversibly changed from a coil to a helix structure. Through modification of the secondary structure, a change in the aggregation number is observed. Thereby, these blockcopolymers may find application in the fabrication of switchable aggregates.

Ice based Cool Thermal Energy Storage (CTES) systems have attracted much attention during last few decades. The reasons are mainly of economical and environmental nature. Compared to conventional refrigeration and air-conditioning systems without cool thermal energy storage, implementation of CTES will increase environmental standards and overall efficiency of the energy systems as it contributes to the phase-out of synthetic refrigerants and reduces peak loads in electricity grids. For the application of a cool thermal energy storages in refrigeration installations and HVAC systems in industry and building sector, it is necessary to have appropriate design tools in order to sufficiently accurate predict their performance. In this thesis theoretical and experimental investigations of two ice based cool thermal energy storage systems, namely static, indirect, external melt, ice-on-coil, i.e. ice bank system and dynamic, ice slurry cool thermal energy storage system are carried out. An ice bank storage technology for cooling purposes is known for a long time. The main drawbacks which are hindering its wider use are the system complexity, high first costs, system efficiency which is highly dependant on design, control and monitoring of the system, etc. On the other hand, ice slurry technology was not well studied until recently, while in the current scientific literature there are still differences between results and conclusions reported by different investigators. The aim of the present thesis is to extend the knowledge in the field of ice based CTES systems, thereby contributing in the development and wider utilization of those systems. In the first part of the thesis a computer application, named “BankaLeda” is presented. It enables simulation of an ice bank system performance. In order to verify developed simulation model an experimental evaluation has been performed. Field measurements have been conducted on a two module silo which was installed as a part of the refrigeration system in dairy and cheese factory “Antun Bohnec” in the city of Ludbreg in Croatia. Experimental findings were compared to the simulation model. The software „BankaLeda“ presents a strong optimization tool for designers and engineers in the field by providing a high degree of freedom in defining particular system design and operating parameters. It offers a basis for assessment and testing of a new energy efficient system arrangements and measures. Besides it will give decisionmakers the ability to test potential solutions in the process of CTES system design. In the second part of the thesis ice slurry pressure drop and heat transfer in horizontal straight tubes have been experimentally investigated. In particular a mixture of 10.3 % of ethanol and water with an initial freezing point of -4.4 °C was considered. It was found that the behaviour of ice slurry flow is changing with time and that ice slurry pressure drop is generally higher than for single phase flow. However for ice concentrations of 15 % and higher, for certain velocities ice slurry pressure drop is found to be of a similar value as for single phase fluid. Moreover, if ice slurry is to be used as a energy transport media it is recommended to keep the ice mass fraction at a level of 20 %. With tube geometry and thermophysical properties of a carrier fluid the heat transfer of ice slurry is generally a function of ice mass fraction and velocity. The imposed heat flux has no or has just minor influence on the heat transfer coefficient. Up to ice mass fraction between 10-15 % the mean heat transfer coefficient shows only slight (laminar flow) or no increase (turbulent flow) in comparison to single phase flow. Beyond that ice mass fraction the heat transfer coefficient is increasing significantly. The test data for pressure drop and heat transfer in laminar and turbulent regime was compared to several correlations from the literature. A new correlations for ice slurry pressure drop and heat transfer in the laminar flow regime, for 10.3 % ethanol and water mixture, were derived based on the present experimental data. The correlation for pressure drop predicts 82 % of the experimental data with ±15 % accuracy, while the correlation for heat transfer predicts 75 % of the data with the same accuracy. In order to investigate advantages and disadvantages of a dynamic, ice slurry system over a static, indirect, external melt, ice-on-coil CTES system and to assess their differences from economical aspects, a theoretical simulation model of an ice slurry CTES have been developed. It was found that the ice slurry based CTES systems posses higher economic and energy saving potential than static type systems. In the best case scenario the total energy consumption of dynamic CTES system was found to be approximately 25 % lower than for a static CTES system. / QC 20100715

In this study, RF coil geometries are designed for MRI applications using inhomogeneous main magnetic fields. The current density distributions that can produce the desired RF magnetic field characteristics are obtained on predefined cubic, cylindrical and planar surfaces and Tikhonov, CGLS, TSVD and Rutisbauer regularization methods are applied to match the desired and generated magnetic fields. The conductor paths, which can produce the current density distribution calculated for each surface selection and regularization technique, are determined using stream functions. The magnetic fields generated by the current distributions are calculated and the error percentages between the desired and generated magnetic fields are found. Optimum conductor paths that are going to be produced on cubic, cylindrical and planar surfaces and the required regularization method are determined on the basis of error percentages and realizability of the conductor paths. The optimum conductor path calculated for the planar coil is realized and in the measurement done by LakeShore 3-Channel Gaussmeter, an average error percentage of 11 is obtained between the theoretical and measured magnetic field. The inductance values of the realized RF coil are measured / the tuning and matching capacitance values are calculated and the frequency characteristics of the system is tested using Electronic Workbench 5.1. The quality factor value of the tested system is found to be 162.5, which corresponds to a bandwidth of 39,2 KHz at 6,387 MHz (operating frequency of METU MRI system). The techniques suggested in this study can be used in order to design and realize RF coils on prede&macr / ned arbitrary surfaces for inhomogeneous main magnetic fields. In addition, a hand held MRI device can be manufactured which uses a low cost permanent magnet to provide a magnetic field and generates the required RF field with the designed RF coil using the techniques suggested in this study.

No description available.

Différentes méthodes ayant pour objectif une utilisation optimale d'antennes radio-fréquences spécialisées en imagerie par résonance magnétique sont développées et validées. Dans un premier temps, il est démontré qu'une méthode alternative de combinaison des signaux provenant des différents canaux de réception d'un réseau d'antennes mène à une réduction significative du biais causé par la présence de bruit dans des images de diffusion, en comparaison avec la méthode de la somme-des-carrés généralement utilisée. Cette réduction du biais engendré par le bruit permet une amélioration de l'exactitude de l'estimation de différents paramètres de diffusion et de diffusion tensorielle. De plus, il est démontré que cette méthode peut être utilisée conjointement avec une acquisition régulière sans accélération, mais également en présence d'imagerie parallèle. Dans une seconde perspective, les bénéfices engendrés par l'utilisation d'une antenne d'imagerie intravasculaire sont étudiés. Suite à une étude sur fantôme, il est démontré que l'imagerie par résonance magnétique intravasculaire offre le potentiel d'améliorer significativement l'exactitude géométrique lors de mesures morphologiques vasculaires, en comparaison avec les résultats obtenus avec des antennes de surface classiques. Il est illustré qu'une exactitude géométrique comparable à celle obtenue grâce à une sonde ultrasonique intravasculaire peut être atteinte. De plus, plusieurs protocoles basés sur une acquisition de type balanced steady-state free-precession sont comparés dans le but de mettre en évidence différentes relations entre les paramètres utilisés et l'exactitude géométrique obtenue. En particulier, des dépendances entre la taille du vaisseau, le rapport signal-sur-bruit à la paroi vasculaire, la résolution spatiale et l'exactitude géométrique atteinte sont mises en évidence. Dans une même optique, il est illustré que l'utilisation d'une antenne intravasculaire permet une amélioration notable de la visualisation de la lumière d'une endoprothèse vasculaire. Lorsque utilisée conjointement avec une séquence de type balanced steady-state free-precession utilisant un angle de basculement spécialement sélectionné, l'imagerie par résonance magnétique intravasculaire permet d'éliminer complètement les limitations normalement engendrées par l'effet de blindage radio-fréquence de l'endoprothèse. / Specific methods for an optimal use of specialized magnetic resonance radiofrequency coils are developed and validated. First, an improved combination of signals from the different channels of an array coil is shown to lead to a significant reduction of the noise bias in diffusion images, in comparison to the generally accepted sum-of-squares combination method. This reduction of the noise bias is demonstrated to greatly improve the accuracy of the estimated diffusion and diffusion tensor parameters, both for a standard non-accelerated acquisition and when parallel imaging is used. In a second scope, the benefits arising from the use of an intravascular imaging antenna are investigated. Using a phantom study, it is demonstrated that intravascular magnetic resonance imaging offers the potential to improve the geometrical accuracy of morphological vascular measurements in comparison to standard surface magnetic resonance imaging and that a geometrical accuracy comparable to the one obtained using intravascular ultrasound can be reached. Several protocols based on a balanced steady-state free-precession sequence are compared in order to highlight the relations between several acquisitions parameters and the achieved geometrical accuracy. In particular, important relations between the vessel size, the vessel wall signal-to-noise ratio, the in-plane resolution and the achieved accuracy are illustrated. In a similar manner, the use of an intravascular antenna is demonstrated to be highly beneficial for an improved in-stent lumen visualization. When used with a balanced steady-state free-precession acquisition with a carefully chosen flip angle, intravascular magnetic resonance imaging can effectively eliminate the hindering aspect of the radiofrequency shielding effect caused by the presence of the vascular stent.

Ces dernières années, la Méthode Intégrale de Volume (MIV) a reçu une attention particulière pour lamodélisation des problèmes électromagnétiques en basse fréquence. Son intérêt principal est l’absencedu maillage de la région air, ce qui rend la méthode légère et rapide. Associée aux méthodes decompression matricielle la MIV devient aujourd'hui une alternative compétitive à la méthode deséléments finis pour la modélisation de dispositifs électromagnétiques ayant un volume d'airprépondérant.Ce rapport porte sur le développement de deux formulations intégrales de volume pour la résolution deproblèmes magnétostatiques avec prise en compte des matériaux non linéaires, des aimants, desbobines, des circuits magnétiques avec ou sans entrefer et des régions minces magnétiques. Lapremière est une formulation en flux de mailles indépendantes basée sur l'interpolation par éléments defacette. La deuxième est une formulation en potentiel vecteur magnétique basée sur l'interpolation paréléments d'arête. L'application de ces formulations permet d’une part d'obtenir des résultats précismême en présence d’un faible maillage et d’autre part de résoudre aisément des problèmes nonlinéaires. Des méthodes de calcul de la force magnétique globale ainsi que du flux magnétique dansles bobines ont été également mises en oeuvre. Les développements informatiques ont été réalisés dansla plateforme MIPSE et ont été validés sur des problèmes académiques ainsi que sur quelquesdispositifs industriels. / In recent years, the Volume Integral Method (VIM) has been received particular attention formodeling of low frequency electromagnetic problems. The main advantage of this method is thatinactive regions do not to be discretized, which makes it light and rapid. Associated with matrixcompression methods, the VIM is a competitive alternative to the finite element method for modelingelectromagnetic devices containing a predominant air volume.This PhD thesis focuses on the development of two volume integral formulations for solvingmagnetostatic problems, in the presence of nonlinear materials, magnets, coils, multiply connectedmagnetic regions, and the presence of magnetic shielding. The first one is a mesh magnetic fluxformulation based on the interpolation of facet elements and the second one is a magnetic vectorpotential formulation based on the interpolation of edge elements. The application of theseformulations provides accurate results even with coarse meshes and allows solving straightforwardnonlinear magnetostatic problems. Methods for computing global magnetic force and magnetic fluxthrough a coil were also implemented as part of this work. Developments performed in the MIPSEplatform were validated on academic case-tests as well as some industrial devices.

Este trabalho apresenta uma metodologia de projeto de atuadores eletromagnéticos lineares inovadora para aplicação em sistemas de suspensão semiativa e ativa. A metodologia, apresentada na forma de fluxograma, define critérios para determinar os requisitos de força e curso que um atuador deve desenvolver considerando um sistema mecânico vibratório com um grau de liberdade com excitação harmônica de base quando o método de controle skyhook é aplicado. Um atuador eletromagnético linear de bobina móvel com duplo arranjo de quase-Halbach que apresenta elevada densidade de força, reduzida massa móvel, ausência de força de relutância e baixa ondulação de força é definido como estudo de caso. Um modelo numérico parametrizado em elementos finitos do comportamento eletromagnético de um passo polar do dispositivo é criado e analisado, considerando restrições dimensionais, com os objetivos de projeto definidos como: elevada densidade de força e reduzida ondulação de força com acionamento brushless CA. Com base no modelo de um passo polar do dispositivo, define-se o volume ativo que o mesmo deve apresentar e, a partir deste, todas as dimensões são definidas de forma a atender os requisitos de projeto. Uma vez definidas as dimensões do atuador com base no modelo eletromagnético, realiza-se a modelagem térmica numérica que permite avaliar qual a máxima densidade de corrente elétrica aplicável de forma que a temperatura, estipulada como máxima, nos enrolamentos não seja excedida. Ainda, a distribuição térmica permite determinar a temperatura de operação dos ímãs permanentes que têm curva de operação dependente da temperatura. A partir dos resultados da simulação térmica e do modelo eletromagnético para um passo polar, realizou-se o acoplamento eletromagnético-térmico por meio da correção das propriedades dos ímãs permanentes e aplicando uma densidade de corrente eficaz dependente das dimensões do modelo parametrizado. O modelo acoplado é simulado e analisado, de modo que as dimensões finais do atuador podem ser obtidas atendendo aos mesmos objetivos de projeto previamente mencionados, respeitando os limites de operação térmica. Adicionalmente, são apresentados modelos analíticos do comportamento eletromagnético e térmico do atuador que podem servir de base para implementação da metodologia proposta, se esta for baseada em modelos analíticos, e podem futuramente ser empregados para a aplicação de otimização matemática do dispositivo. Por fim, um protótipo do dispositivo é construído de forma a validar a metodologia proposta. Com este protótipo são realizados ensaios de densidade de fluxo magnético no entreferro, tensão induzida a vazio, força estática e ensaio dinâmicos com o dispositivo instalado em uma bancada de testes de vibrações controladas desenvolvida durante o projeto. Os resultados mostram a eficácia da metodologia proposta, uma vez que os resultados experimentais mostraram boa concordância com os resultados esperados. / This work presents an innovative linear electromagnetic actuator design methodology for application in semi-active and active suspension systems. The methodology, synthesized in a flowchart, sets criteria to determine requirements such as axial force and stroke that an actuator should develop considering a vibration system with one degree of freedom with harmonic base excitation when the skyhook control method is applied. A linear moving-coil electromagnetic actuator with dual quasi-Halbach arrays of permanent magnets that presents high force density, low moving-mass, no reluctance force and low force ripple is defined as a case study. A finite element numerical parameterized model that describes the electromagnetic behavior of one pole pitch of the device is created and analyzed, considering dimensional constraints, with the design objectives defined as: high force density and low ripple of force with brushless AC drive. Based on the model of one pole pitch of the device the active volume and all dimensions are defined in order to meet the design requirements. Once the actuator dimensions are defined, based on the electromagnetic model, a numerical thermal model was constructed, which allows to evaluate the maximum applicable electric current density so that the maximum temperature at the windings is not exceeded. Furthermore, the thermal distribution gives the operating temperature of the permanent magnets, which present performance highly dependent on temperature. With the results of the thermal simulation, the electromagnetic-thermal coupling is performed by correcting permanent magnet properties and by applying a parametric-dependent effective current density. The coupled model is simulated and analyzed so that the final dimensions of the actuator can be obtained with the same design objectives previously mentioned, while respecting thermal operating limits. In addition, the work presents analytical models of the electromagnetic and thermal behavior of the actuator that can be the basis for implementation of the proposed methodology, if it is based on analytical models, and can further be used for the application of mathematical optimization of the device. Finally, a prototype was built to validate the proposed method. Measurements were carried out to assess magnetic flux density in the air gap, open-circuit induced voltage, static force and dynamic tests with the device installed in a test bench that was developed during this work. The results show the effectiveness of the proposed method since experimental results have shown good agreement with the expected results.

Este trabalho apresenta uma metodologia de projeto de atuadores eletromagnéticos lineares inovadora para aplicação em sistemas de suspensão semiativa e ativa. A metodologia, apresentada na forma de fluxograma, define critérios para determinar os requisitos de força e curso que um atuador deve desenvolver considerando um sistema mecânico vibratório com um grau de liberdade com excitação harmônica de base quando o método de controle skyhook é aplicado. Um atuador eletromagnético linear de bobina móvel com duplo arranjo de quase-Halbach que apresenta elevada densidade de força, reduzida massa móvel, ausência de força de relutância e baixa ondulação de força é definido como estudo de caso. Um modelo numérico parametrizado em elementos finitos do comportamento eletromagnético de um passo polar do dispositivo é criado e analisado, considerando restrições dimensionais, com os objetivos de projeto definidos como: elevada densidade de força e reduzida ondulação de força com acionamento brushless CA. Com base no modelo de um passo polar do dispositivo, define-se o volume ativo que o mesmo deve apresentar e, a partir deste, todas as dimensões são definidas de forma a atender os requisitos de projeto. Uma vez definidas as dimensões do atuador com base no modelo eletromagnético, realiza-se a modelagem térmica numérica que permite avaliar qual a máxima densidade de corrente elétrica aplicável de forma que a temperatura, estipulada como máxima, nos enrolamentos não seja excedida. Ainda, a distribuição térmica permite determinar a temperatura de operação dos ímãs permanentes que têm curva de operação dependente da temperatura. A partir dos resultados da simulação térmica e do modelo eletromagnético para um passo polar, realizou-se o acoplamento eletromagnético-térmico por meio da correção das propriedades dos ímãs permanentes e aplicando uma densidade de corrente eficaz dependente das dimensões do modelo parametrizado. O modelo acoplado é simulado e analisado, de modo que as dimensões finais do atuador podem ser obtidas atendendo aos mesmos objetivos de projeto previamente mencionados, respeitando os limites de operação térmica. Adicionalmente, são apresentados modelos analíticos do comportamento eletromagnético e térmico do atuador que podem servir de base para implementação da metodologia proposta, se esta for baseada em modelos analíticos, e podem futuramente ser empregados para a aplicação de otimização matemática do dispositivo. Por fim, um protótipo do dispositivo é construído de forma a validar a metodologia proposta. Com este protótipo são realizados ensaios de densidade de fluxo magnético no entreferro, tensão induzida a vazio, força estática e ensaio dinâmicos com o dispositivo instalado em uma bancada de testes de vibrações controladas desenvolvida durante o projeto. Os resultados mostram a eficácia da metodologia proposta, uma vez que os resultados experimentais mostraram boa concordância com os resultados esperados. / This work presents an innovative linear electromagnetic actuator design methodology for application in semi-active and active suspension systems. The methodology, synthesized in a flowchart, sets criteria to determine requirements such as axial force and stroke that an actuator should develop considering a vibration system with one degree of freedom with harmonic base excitation when the skyhook control method is applied. A linear moving-coil electromagnetic actuator with dual quasi-Halbach arrays of permanent magnets that presents high force density, low moving-mass, no reluctance force and low force ripple is defined as a case study. A finite element numerical parameterized model that describes the electromagnetic behavior of one pole pitch of the device is created and analyzed, considering dimensional constraints, with the design objectives defined as: high force density and low ripple of force with brushless AC drive. Based on the model of one pole pitch of the device the active volume and all dimensions are defined in order to meet the design requirements. Once the actuator dimensions are defined, based on the electromagnetic model, a numerical thermal model was constructed, which allows to evaluate the maximum applicable electric current density so that the maximum temperature at the windings is not exceeded. Furthermore, the thermal distribution gives the operating temperature of the permanent magnets, which present performance highly dependent on temperature. With the results of the thermal simulation, the electromagnetic-thermal coupling is performed by correcting permanent magnet properties and by applying a parametric-dependent effective current density. The coupled model is simulated and analyzed so that the final dimensions of the actuator can be obtained with the same design objectives previously mentioned, while respecting thermal operating limits. In addition, the work presents analytical models of the electromagnetic and thermal behavior of the actuator that can be the basis for implementation of the proposed methodology, if it is based on analytical models, and can further be used for the application of mathematical optimization of the device. Finally, a prototype was built to validate the proposed method. Measurements were carried out to assess magnetic flux density in the air gap, open-circuit induced voltage, static force and dynamic tests with the device installed in a test bench that was developed during this work. The results show the effectiveness of the proposed method since experimental results have shown good agreement with the expected results.