Dissertations / Theses on the topic 'Electromagnetic-Based modeling'

A new electromagnetic model is established based on an average rate of directional time-distance energy transfers. A directional time-distance energy transfer is defined as an energy carrier mediator (boson) exchange. Electromagnetic force is modeled as mean valued, continual emission and absorption of energy carrier mediators.

For an isolated, spherically symmetric static charge distribution, Maxwell's stress equation is recast using a variant of Stokes' Theorem. The recast stress equation eliminates the stress normal to the electric field and establishes a stress only aligned with the electric field. The remaining stress is identified as an external omnidirectional Poincaré stress, inwardly directed towards the charge distribution. The Poincaré stress is modeled as a mean valued, continual exchange of bosons between the charge distribution and the distant matter of the universe.

For two separated, spherically symmetric static charge distributions, Maxwell's stress equation is recast using a variant of Stokes' Theorem. The recast stress equation develops a line stress that only exists on the straight path between the two charge distributions. The line stress is identified as a Coulomb stress modeled as a mean valued, continual exchange of photons back and forth between two like-charge distributions.

For an isolated, differential current element, Maxwell's stress equation is recast using a variant of Stokes' Theorem. The recast stress equation establishes a pinch stress that is normal to the magnetic field and is directed inward toward the differential current element. Similar to the Poincaré stress, the pinch stress is omnidirectional and is modeled as a mean valued, continual exchange of bosons between the current element and the distant matter of the universe.

For two separated, static differential current elements, a Neumann stress is established by analyzing the historical current force formulas known to be compatible with Maxwell's equations for closed circuits. The term Neumann stress is assigned to the line stress that only exists at each point on the straight path between two separated, differential current elements. Similar to the Coulomb stress, the Neumann stress is modeled as a mean valued, continual exchange of photons back and forth between two differential current elements in opposite directions.

The advances in nanoscience and nanotechnology in recent decades have renewed the interests in the optical properties of metals. Today, the field known as Plasmonics studies the control and manipulation of the electromagnetic near-fields of metallic nanostructures in order to realize novel subwavelength optical applications. In particular, this thesis explores the phenomenon of plasmon resonance for molecular sensing. Surface plasmon resonance (SPR) on flat metal surfaces is used for index-of-refraction sensing and localized surface plasmon resonance (LSPR) on metal nanospheres can produce surface-enhanced Raman scattering (SERS). The operation principles and the experimental evaluation of two SPR sensing devices are presented. An integrated sensor and a 2D wavelength-angle modulated version were estimated to have an angular sensitivity of 126°/RIU and 91°/RIU, respectively. Furthermore, through an implementation of a full vector multiple-multipole light scattering method, useful for the calculations of the field focusing efficiency between assemblies of metal nanospheres, we showed that optical frequency electric fields can be enhanced in gold nanoparticle assemblies by an order of 450 in nanometer volumes. Keywords: surface plasmons, plasmonics, optical biosensors, surface-enhanced Raman scattering, optics of metals, nanophotonics, nanomaterials, classical electrodynamics
L'avancée des nanosciences et de la nanotechnologie au cours des dernières décennies a suscité un renouvellement de l'intérêt pour les propriétés optiques des métaux. Aujourd'hui, la Plasmonique cherche à contrôler les champs proches électromagnétiques des nanostructures métalliques afin de bénéficier des nouvelles applications reposant sur l'optique de sous-longueur d'onde. En particulier, ce mémoire explore l'utilisation de la résonance à plasmons pour la capture des molécules. L'étude se divise en la résonance à plasmons de surface (SPR) pour des surfaces métalliques planes et pour des nanosphères métalliques. Ces deux méthodes permettent de créer des capteurs sensibles aux variations d'indice de réfraction et d'autres qui reposent sur des effets non-linéaires tels que la diffusion Raman exaltée de surface (SERS). Suite à l'introduction des bases, l'opération ainsi que des résultats expérimentaux de deux capteurs à plasmons de surface sont présentés. Un capteur intégré et une version 2D avec modulation de longueur d'onde et de l'angle possèdent une sensibilité angulaire d'environ 126°/RIU et 91°/RIU, respectivement. Par la suite, la réalisation de la méthode du multiple-multipole, utile pour évaluer l'efficacité de la concentration des champs entre des nanosphères métalliques, est discutée. Une amélioration de la concentration de champ optique de l'ordre de 450 par des nanospheres d'or est présentée. Mots-clés: plasmon de surface, plasmonique, biocapteurs optiques, diffusion Raman exaltée de surface, optique des métaux, nanophotonique, nanomatériel, électro-dynamique classique

2010 - 2011
In several applications for the aeronautic, automative and electronic industries, there is an increasing demand of structural nanocomposites exhibiting remarkable thermal and mechanical properties and, at the same time, tailored and controlled electromagnetic (EM) performances. The interest and the scientific importance of the topic is justified by the fact that the conventional materials do not have the suitable properties to satisfy the specific requirements for modern applications. Instead, two or more distinct materials may be combined to form a material which possesses superior properties, with respect to those of individual components. Thus the individuation and preparation of advanced composites with best features respect to the traditional materials is currently required in several industrial sectors. Since CNTs can be exploited with varying structural and physical properties, geometry and functionality, that result in a different dispersion and adhesion with the polymer matrix, the possible range of composite material properties can be very large... [edited by author]
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The low-frequency electromagnetic compatibility (EMC) is an increasingly important aspect in the design of practical systems to ensure the functional safety and reliability of complex products. The opportunities for using numerical techniques to predict and analyze system’s EMC are therefore of considerable interest in many industries. As the first phase of study, a proper model, including all the details of the component, was required. Therefore, the advances in EMC modeling were studied with classifying analytical and numerical models. The selected model was finite element (FE) modeling, coupled with the distributed network method, to generate the model of the converter’s components and obtain the frequency behavioral model of the converter. The method has the ability to reveal the behavior of parasitic elements and higher resonances, which have critical impacts in studying EMI problems. For the EMC and signature studies of the machine drives, the equivalent source modeling was studied. Considering the details of the multi-machine environment, including actual models, some innovation in equivalent source modeling was performed to decrease the simulation time dramatically. Several models were designed in this study and the voltage current cube model and wire model have the best result. The GA-based PSO method is used as the optimization process. Superposition and suppression of the fields in coupling the components were also studied and verified. The simulation time of the equivalent model is 80-100 times lower than the detailed model. All tests were verified experimentally. As the application of EMC and signature study, the fault diagnosis and condition monitoring of an induction motor drive was developed using radiated fields. In addition to experimental tests, the 3DFE analysis was coupled with circuit-based software to implement the incipient fault cases. The identification was implemented using ANN for seventy various faulty cases. The simulation results were verified experimentally. Finally, the identification of the types of power components were implemented. The results show that it is possible to identify the type of components, as well as the faulty components, by comparing the amplitudes of their stray field harmonics. The identification using the stray fields is nondestructive and can be used for the setups that cannot go offline and be dismantled

This thesis has been motivated by the growing needs for multi-degree of freedom (M-DOF) electromagnetic actuators capable of smooth and accurate multi-dimensional driving motions. Because high coercive rare-earth permanent-magnets (PMs) are widely available at low cost, their uses for developing compact, energy-efficient M-DOF actuators have been widely researched. To facilitate design analysis and optimization, this thesis research seeks to develop a general method based on distributed source models to characterize M-DOF PM-based actuators and optimize their designs to achieve high torque-to-weight performance with compact structures To achieve the above stated objective, a new method that is referred to here as distributed multi-level current (DMC) utilizes geometrically defined point sources has been developed to model electromagnetic components and phenomena, which include PMs, electromagnets (EMs), iron paths and induced eddy current. Unlike existing numerical methods (such as FEM, FDM, or MLM) which solve for the magnetic fields from Maxwell’s equations and boundary conditions, the DMC-based method develops closed-form solutions to the magnetic field and force problems on the basis of electromagnetic point currents in a multi-level structure while allowing trade-off between computational speed and accuracy. Since the multi-level currents can be directly defined at the geometrically decomposed volumes and surfaces of the components (such as electric conductors and magnetic materials) that make up of the electromagnetic system, the DMC model has been effectively incorporated in topology optimization to maximize the torque-to-weight ratio of an electromechanical actuator. To demonstrate the above advantages, the DMC optimization has been employed to optimize the several designs ranging from conventional single-axis actuators, 2-DOF linear-rotary motors to 3-DOF spherical motors. The DMC modeling method has been experimentally validated and compared against published data. While the DMC model offers an efficient means for the design analysis and optimization of electromechanical systems with improved computational accuracy and speed, it can be extended to a broad spectrum of emerging and creative applications involving electromagnetic systems.

The main objective for physics based modeling of the power converter components is to design the whole converter with respect to physical and operational constraints. Therefore, all the elements and components of the energy conversion system are modeled numerically and combined together to achieve the whole system behavioral model. Previously proposed high frequency (HF) models of power converters are based on circuit models that are only related to the parasitic inner parameters of the power devices and the connections between the components. This dissertation aims to obtain appropriate physics-based models for power conversion systems, which not only can represent the steady state behavior of the components, but also can predict their high frequency characteristics. The developed physics-based model would represent the physical device with a high level of accuracy in predicting its operating condition. The proposed physics-based model enables us to accurately develop components such as; effective EMI filters, switching algorithms and circuit topologies [7]. One of the applications of the developed modeling technique is design of new sets of topologies for high-frequency, high efficiency converters for variable speed drives. The main advantage of the modeling method, presented in this dissertation, is the practical design of an inverter for high power applications with the ability to overcome the blocking voltage limitations of available power semiconductor devices. Another advantage is selection of the best matching topology with inherent reduction of switching losses which can be utilized to improve the overall efficiency. The physics-based modeling approach, in this dissertation, makes it possible to design any power electronic conversion system to meet electromagnetic standards and design constraints. This includes physical characteristics such as; decreasing the size and weight of the package, optimized interactions with the neighboring components and higher power density. In addition, the electromagnetic behaviors and signatures can be evaluated including the study of conducted and radiated EMI interactions in addition to the design of attenuation measures and enclosures.

L'émergence de l'environnement radio intelligent (SRE) en tant que nouveau paradigme qui remet en question le status quo dans la communication sans fil a motivé l'utilisation des surface intelligentes reconfigurables (RIS) basées sur des métasurfaces pour améliorer la limite de performance des systèmes de communication sans fil. L'objectif principal de cette thèse est la modélisation d'un système de communication assisté par un RIS à l'aide d'approches basées sur l'électromagnétisme.Le Chapitre 1 présente le concept d'environnement radio intelligent. Nous donnons également la définition du RIS et comment le RIS peut être utilisé dans le contexte du SRE. Nous donnons aussi quelques perspectives historiques et discutons le développement des activités de recherche dans ce contexte.Le Chapitre 2 présente les concepts théoriques nécessaires pour comprendre les résultats des chapitres suivants. Ce chapitre est divisé en deux parties. La première partie traite de la modélisation des métasurfaces où nous passons d'une description microscopique basée sur la physique d'une métasurface et introduisons une représentation macroscopique de celle-ci, qui s'avère appropriée pour une application aux communications sans fil. La deuxième partie présente plusieurs approches analytiques qui nous permettent de calculer le champ électromagnétique dans un certain volume..Le Chapitre 3 fournit une comparaison des performances entre les RISs fonctionnant comme des réflecteurs anormaux et un schéma de relais basé sur le décodage et la transmission. La comparaison est qualitative et couvre une multitude de métriques. En outre, une comparaison quantitative en termes de débits de données réalisables est également présentée. En particulier, les résultats numériques montrent que des RISs suffisamment grands peuvent être plus performants que les systèmes assistés par relais en termes de débit de données, tout en réduisant la complexité.Le Chapitre 4 propose une caractérisation analytique du champ électromagnétique en présence d'un RIS qui est modélisé comme une métasurface homogénéisée et qui fonctionne soit en réflexion ou transmission. Des expressions de forme fermée sont également obtenues dans deux régimes asymptotiques qui sont représentatifs de deux déploiements en champ lointain et en champ proche. Sur la base de l'approche proposée, l'impact de plusieurs paramètres est étudié.Enfin, le Chapitre 5 résume la thèse et discute des perspectives futures qui méritent d'être étudiées pour mieux comprendre les avantages et les inconvénients des RISs pour application aux communications sans fil
The emergence of smart radio environment (SRE) as a new paradigm that challenges the status quo in wireless communication has motivated the use of metasurface-based reconfigurable intelligent surface (RIS) to improve the performance limits in wireless communication systems. The main focus of this thesis is the modeling of reconfigurable intelligent surfaces (RIS)-aided communication systems using electromagnetic based methods.Chapter 1 introduces the concept of smart radio environment. We also give the definition of RIS and how RIS can be used in context of SRE. To give some historical perspectives, we also discuss several important milestone papers throughout the development of research activities that lead to the current state of the art.Chapter 2 introduces theoretical concepts that are necessary to understand the results in the subsequent chapters. This chapter is divided into two parts. The first part discusses the metasurfaces modeling where we move from a physics-based microscopic description of a metasurface and introduces a macroscopic representation for it, which is shown to be suitable for application in wireless communications. The second part introduces several analytical approaches that allow us to compute the EM field at any point of a given volume that contains the metasurface.Chapter 3 provides a performance comparison between RISs operating as anomalous reflectors and a decode-and-forward relaying scheme that is representative of competing candidate technologies to realize SREs. The comparison is qualitative and covers multitude metrics. Furthermore, a quantitative comparison in terms of achievable data rates is presented. In particular, the numerical results show that sufficiently large RISs can outperform relay-aided systems in terms of data rate, while reducing the implementation complexity.Chapter 4 proposes an electromagnetic-based analytical characterization of the free-space path-loss of a wireless link in the presence of a RIS that is modeled as a two-dimensional homogenized metasurface made of sub-wavelength scattering elements and that operate either in reflection or transmission mode. The analytical method of physical optics is employed. Closed-form expressions are also obtained in two asymptotic regimes that are representative of far-field and near-field deployments. Based on the proposed approach, the impact of several design parameters and operating regimes is unveiled.Finally, Chapter 5 summarizes the main findings of the thesis and discusses possible future directions that are worth investigating to unlock the full potential of RIS and bring it into practice

During this PhD study, several finite-difference time-domain (FDTD) methods were developed to numerically investigate coordinate transformation based metamaterial devices. A novel radially-dependent dispersive FDTD algorithm was proposed and applied to simulate electromagnetic cloaking structures. The proposed method can ac- curately model both lossless and lossy cloaks with ideal or reduced parameters. It was demonstrated that perfect “invisibility” from electromagnetic cloaks is only available for lossless metamaterials and within an extremely narrow frequency band. With a few modifications the method is able to simulate general media, such as concentrators and rotation coatings, which are produced by means of coordinate transformations techniques. The limitations of all these devices were thoroughly studied and explo- red. Finally, more useful cloaking structures were proposed, which can operate over a broad frequency spectrum. Several ways to control and manipulate the loss in the electromagnetic cloak ba- sed on transformation electromagnetics were examined. It was found that, by utili- sing inherent electric and magnetic losses of metamaterials, as well as additional lossy materials, perfect wave absorption can be achieved. These new devices demonstrate super-absorptivity over a moderate wideband range, suitable both for microwave and optical applications. Furthermore, a parallel three-dimensional dispersive FDTD method was introdu- ced to model a plasmonic nanolens. The device has its potential in subwavelength imaging at optical frequencies. The finiteness of such a nano-device and its impact on the system dynamic behaviour was numerically exploited. Lastly, a parallel FDTD method was also used to model another interesting coordinate transformation based device, an optical black hole, which can be characterised as an omnidirectional broad- band absorber.

L’intégration des systèmes mécatroniques génère de nombreuses perturbations multi-physiques (thermiques, électromagnétiques et dynamiques) rendant leur choix d’architecture complexe. En effet, l’introduction croissante de composants électroniques et électriques (E/E) dans la plupart des systèmes actuels, augmente le risque d’occurrence de nombreuses interférences électromagnétiques (IEM) pouvant dégrader fortement leur fonctionnement. Tandis que ces problèmes de compatibilité électromagnétique (CEM) sont généralement traités en phase de conception détaillée, où les possibilités de compromis se limitent à quelques ajustements de positionnement ou à des solutions de protection coûteuses, une solution consiste à proposer un cadre collaboratif pour l’évaluation, dès les premières phases de conception, d’architectures physiques de concept prenant en compte ces contraintes électromagnétiques (EM). En effet, il est important à cette étape, que l’ensemble des acteurs multidisciplinaires impliqués puissent définir, modifier/mettre à jour, ajouter leurs connaissances et contraintes et échanger leurs données tout en continuant à travailler dans leur environnement numérique habituel. Par ailleurs, ces activités d’ingénierie système doivent être outillées avec des approches d’« Ingénierie Système basée sur des modèles » (MBSE), pour supporter la continuité numérique, la cohérence et la traçabilité des modèles et des données nécessaires à ce processus d’évaluation.Pour répondre à ce besoin, cette thèse s’appuie sur l’approche collaborative MBSE SAMOS (Spatial Architecture based on Multi-physics and Organization of Systems) afin de supporter l'évaluation de l'architecture 3D de concept en phase amont sous contraintes électromagnétiques. Dans ce contexte, nous avons, dans un premier temps, développé une extension SysML appelée EMILE (ElectroMagnetic Interactions Layout Extension) pour formaliser et modéliser, au plus tôt, les contraintes EM dans le modèle système.Cette extension inclut notamment la définition des exigences EM, la description des modes de couplage électromagnétiques et la spécification des configurations de simulation permettant la vérification et la validation ultérieures des exigences, grâce au développement d’une interface homme-machine. Notre travail de recherche a ensuite porté sur une méthodologie d’évaluation combinant une approche topologique avec une modélisation EM., afin de supporter le processus d'évaluation qualitative et quantitative des interférences électromagnétiques (IEM). En effet, pour un type d’IEM donné, l'analyse topologique de l’architecture système permet d'identifier qualitativement l'existence des composants victimes et de leurs agresseurs potentiels associés. Une fois ces IEM potentielles identifiées, une évaluation quantitative peut alors être réalisée, par exemple en se basant sur les équations et lois physiques du couplage identifié, et sur les exigences électromagnétiques et géométriques prédéfinies avec EMILE. Cette approche permet ainsi de garantir le choix pertinent d’une architecture physique 3D de concept sous contraintes EM. Les approches proposées ont été illustrées sur une étude de cas d'une chaîne de traction du véhicule électrique, en s’appuyant sur plusieurs scénarios d’implémentation logicielle (SysML, Modelica, Matlab, FreeCAD) au sein de l’outil Sketcher 3D EM
The integration of mechatronic systems generates many multi-physical disturbances (thermal, electromagnetic and dynamic) making their choice of architecture complex. Indeed, the increasing introduction of electronic and electrical (E/E) components in most of the current systems, increases the risk of occurrence of many electromagnetic interferences (EMI) that can strongly degrade their behavior. While these electromagnetic compatibility (EMC) problems are usually addressed in the detailed design phase, where the possibilities of compromise are limited to a few positioning adjustments or costly protection solutions, one solution is to propose a collaborative framework for the evaluation, from the early design phases, of physical design architectures taking into account these electromagnetic (EM) constraints. Actually, it is important at this stage that all the multidisciplinary actors involved can define, modify/update, add their knowledge and constraints and exchange their data while continuing to work in their usual digital environment. In addition, these system engineering activities must be supported with "Model-Based System Engineering" (MBSE) approaches, to support the digital continuity, consistency and traceability of the models and data required for this evaluation process.To meet this need, this thesis is based on the MBSE SAMOS (Spatial Architecture based on Multi-physics and Organization of Systems) collaborative approach to support, from the preliminary design phase, the evaluation of the 3D concept architecture under electromagnetic constraints. In this context, we have initially developed a SysML extension called EMILE (ElectroMagnetic Interactions Layout Extension) to formalize and model, as early as possible, the EM constraints in the system model.This extension notably includes the definition of EM requirements, the description of electromagnetic coupling modes and the specification of simulation configurations allowing the further verification and validation of the requirements, thanks to the development of a Human-Machine Interface. Our research work then focused on an evaluation methodology combining a topological approach with EM modeling, in order to support the process of qualitative and quantitative evaluation of electromagnetic interference (EMI). Indeed, for a given type of EMI, the topological analysis of the system architecture allows to qualitatively identify the existence of the victim components and their associated potential aggressors. Once these potential EMIs have been identified, a quantitative evaluation can then be performed, for example based on the physical equations and laws of the identified coupling, and on the electromagnetic and geometric requirements predefined with the EMILE extension. As a result, this approach ensures the relevant choice of a 3D physical architecture of the concept under EM constraints. The proposed approaches have been illustrated on a case study of an electric vehicle power train, based on various software implementation scenarios (SysML, Modelica, Matlab, FreeCAD) within the Sketcher 3D EM tool

The aim of the present thesis is to improve and optimize a Thomson coil based actuatorfor medium voltage vacuum interrupters. The Thomson coil based actuator’s concept isdiscussed. The thesis presents analytical as well as finite element models of the actuatoralong with a comparison of their results. Several experimental setups have been built forthis degree project and they are described in the thesis. Measurements from these setupsare also compared to simulation results. The thesis concludes by drawing conclusionsfrom the compared results and proposes possible directions for additional work in thenear future.
Målsättningen för denna uppsats är att förbättra och optimera en aktuator för mellanspänningsvakuumbrytare baserad på en Thomsonspole. Aktuatorkonceptet analyserasoch diskuteras. Uppsatsen presenterar analytiska modeller såväl som numeriska modellerför FEM av aktuatorn, samt jämförelser av resultaten från simuleringar gjorda av dessa.Flera experimentuppställningar har byggts under detta examensprojekt och beskrivs idenna uppsatsen. Mätningar från dessa uppställningar jämförs också med resultaten frånsimuleringarna. Uppsatsen drar slutligen slutsatser utifrån resultaten och föreslår möjligavägar för ytterligare arbete på området inom en snar framtid.

In this thesis, quadratic hexahedral edge elements have been applied to the three dimensional for open region electromagnetic scattering problems. For this purpose, a semi-automatic all-hexahedral mesh generation algorithm is developed and implemented. Material properties inside the elements and along the edges are also determined and prescribed during the mesh generation phase in order to be used in the solution phase. Based on the condition number quality metric, the generated mesh is optimized by means of the Particle Swarm Optimization (PSO) technique. A framework implementing hierarchical hexahedral edge elements is implemented to investigate the performance of linear and quadratic hexahedral edge elements. Perfectly Matched Layers (PMLs), which are implemented by using a complex coordinate transformation, have been used for mesh truncation in the software. Sparse storage and relevant efficient matrix ordering are used for the representation of the system of equations. Both direct and indirect sparse matrix solution methods are implemented and used. Performance of quadratic hexahedral edge elements is deeply investigated over the radar cross-sections of several curved or flat objects with or without patches. Instead of the de-facto standard of 0.1 wavelength linear element size, 0.3-0.4 wavelength quadratic element size was observed to be a new potential criterion for electromagnetic scattering and radiation problems.

Supplying wireless sensors from ambient energy is nowadays highly demanded for a higher flexibility of use and low system maintenance costs. Vibration sources are thereby especially attractive due to their availability and the relatively high energy density they can provide. The aim of this work is to realize a hybrid energy converter for vibration sources having low amplitude and low frequency. The idea is to combine two diverse harvesters to realize a higher energy density and at the same time to improve the converter reliability. We focus on the design, modeling, and test of the hybrid vibration converter. For an appropriate converter design, the vibration profiles of several ambient vibration sources are characterized. The results show that the typical frequency and acceleration ranges are between 5 Hz to 60 Hz and 0.1 g to 1.5 g respectively. The proposed converter is based on the magnetoelectric (ME) and electromagnetic (EM) principles. These two principles can be easily combined within almost the same volume, because they generate energy form the same varying magnetic field coupled to the mechanical vibration of the source. Thereby, the energy density is improved as the ME converter is incorporated within the relatively large coil housing of the electromagnetic converter. The proposed converter is based on the use of a magnetic spring instead of the typically used mechanical springs, which applies the repulsive force to the seismic mass of the converter. The applied vibration is transmitted to the converter based on the magnetic spring principle instead of the conventional mechanical springs. Due to the nonlinearity of the magnetic spring, the converter is able to operate for a frequency bandwidth instead of resonant frequency which is the case while using a mechanical spring. Hence, this leads to realize a high converter efficiency even under random vibrations characterized by frequency bandwidth. As well, using magnetic spring principle enables to adjust the resonant frequency of the converter relative to the applied vibration source easily by just adjusting the moving magnet size. For the converter design, a parametric study is conducted using finite element analysis. Two main criteria are thereby taken into account, which are the compactness and the efficiency of the converter. Parameters affecting these two criteria are classified in mechanical, electromagnetic and magnetoelectric parameters. Results show that the combination of the EM and ME principles leads to an improvement of the energy output compared to a single EM or ME converter. The novel hybrid converter is realized and tested under harmonic and real vibration profiles. It comprises two main parts: A fixed part, where the coils and the ME transducer are fixed in order to ensure a good reliability of the converter by avoiding wire movements. A moving part, where the moving magnet of the magnetic spring and the magnetic circuit are placed. The presented converter is reliable and compact, which is able to harvest energy with a maximum output power density of 0.11 mW/cm³ within a frequency bandwidth of 12 Hz for a resonance frequency of 24 Hz under an applied harmonic vibration with an amplitude of 1 mm.
Die Versorgung von drahtlosen Sensoren aus der Umgebungsenergie ermöglicht heutzutage eine hohe Einsatzflexibilität und die Senkung des Systemwartungsaufwands. Schwingungsquellen sind aufgrund ihrer Verfügbarkeit und der damit erreichbaren Energiedichte besonders attraktiv. Ziel dieser Arbeit ist es, einen hybriden Energiewandler für Vibrationsquellen mit geringer Amplitude und niedriger Frequenz zu realisieren. Der Ansatz dabei ist, zwei verschiedene Wandler zu kombinieren, um eine höhere Energiedichte zu erreichen und die Zuverlässigkeit zu verbessern. Der Entwurf konzentriert sich auf die Modellierung und den Test des hybriden Vibrationswandlers. Für einen geeigneten Wandlerentwurf werden die Schwingungsprofileigenschaften mehrerer Umgebungsschwingungsquellen untersucht. Die Ergebnisse zeigen, dass die typische Frequenz zwischen 5 Hz und 60 Hz und der Beschleunigungsbereich zwischen 0,1 g und 1,5 g liegen. Der vorgeschlagene Wandler kombiniert das magnetoelektrischen (ME) Prinzip mit dem elektromagnetischen (EM) Prinzip. Diese beiden Prinzipien können innerhalb des fast gleichen Volumens leicht integriert werden, da sie Energie aus der Variation des gleichen Magnetfeldes, das mit der mechanischen Schwingung gekoppelt ist, erzeugen können. Dadurch wird die Energiedichte verbessert, da der ME-Wandler in das relativ große Spulengehäuse des elektromagnetischen Wandlers eingesetzt werden kann. Darüber hinaus basiert der vorgeschlagene Wandler auf der Verwendung von Magnetfedern, um die Repulsivkraft auf die seismische Masse zu realisieren. Aufgrund der Nichtlinearität der Magnetfeder, kann der Wandler in einem breiteren Frequenzbereich betrieben werden, anstatt nur bei der Resonanzfrequenz, wie es bei der Verwendung einer mechanischen Feder der Fall ist. Dies führt dazu, dass der Wandler auch bei zufälligen breitbandigen Schwingungsquellen effizient betrieben werden kann. Darüber hinaus ermöglicht die Verwendung des Magnetfederprinzips eine einfache Einstellung der Resonanzfrequenz des Wandlers in Bezug auf die Schwingungsquelle, durch Einstellen der Größe des beweglichen Magneten. Für den Wandlerentwurf wird eine Parameterstudie mit Hilfe der Finite-Elemente-Analyse durchgeführt. Zwei Hauptkriterien werden dabei berücksichtigt: Die Kompaktheit und die Energieeffizienz des Wandlers. Parameter die diese beiden Kriterien beeinflussen, können in mechanische, elektromagnetische und magnetoelektrische unterteilt werden. Die Ergebnisse haben gezeigt, dass die Kombination der EM- und ME-Prinzipien zu einer Verbesserung der Energieausbeute im Vergleich zu einem einzelnen EM- oder ME-Wandler geführt hat. Der neuartige Hybrid-Wandler wurde realisiert und unter harmonischen und realen Schwingungsprofilen getestet. Der Wandler besteht aus zwei Hauptteilen: Ein festes Teil, an dem die Spulen und der ME-Wandler befestigt sind, um eine hohe Zuverlässigkeit zu gewährleisten indem auf einen beweglichen Draht verzichtet wird, und ein bewegliches Teil, das sich aus einem beweglichen Magneten zusammensetzt. Der vorgestellte Wandler ist zuverlässig, kompakt und in der Lage, Energie mit einer maximalen Ausgangsleistungsdichte von 0,11 mW/cm 3 und einer Bandbreite von 12 Hz bei einer Resonanzfrequenz von 24 Hz unter einer angelegten harmonischen Schwingung mit einer Amplitude von 1 mm zu gewinnen.

La plasmonique basée sur les matériaux 2D est un domaine en plein essor dans la photonique, avec des implications technologiques potentielles révolutionnaires dans des domaines aussi variés que le diagnostic, l'énergie et la communication. Le graphène, un matériau 2D unique et doté d'excellentes propriétés plasmoniques, est une alternative prometteuse aux métaux nobles conventionnels dans le domaine de la plasmonique, notamment en raison de ses propriétés accordables en fréquence. Le graphène est modélisé dans cette thèse comme une feuille conductrice infiniment mince dans le cadre des éléments finis (vectoriels) de Galerkin, par opposition aux modèles plus conventionnels où la feuille de graphène est considérée comme ayant une épaisseur finie. Une seconde étude 2D rigoureuse du comportement du champ électromagnétique le long de la direction de propagation dans un guide d'ondes ouvert est réalisée en modélisant le graphène comme un diffuseur (1D) qui agit comme une perturbation locale au guide. Enfin, l'important décalage d’indice effectif qui existe entre le mode du guide d'ondes dielectrique et le mode plasmonique du graphène altère le couplage. Pour surmonter ce problème, un coupleur est conçu à l'aide du formalisme direct en champ diffracté développé. Des études approfondies du phénomène de battement observé dans le coupleur sont également réalisées. Plusieurs études impliquant les différents ordres de diffraction du réseau coupleur, l'épaisseur du guide d'ondes, etc. sont menées. Les paramètres du coupleur sont ensuite optimisés pour obtenir un coupleur à réseau compact et intégré à base de graphène dont l'efficacité atteint 80% à dans l’infrarouge
Plasmonics based on 2D materials is a burgeoning field in photonics with potential groundbreaking technological implications for diagnostics, energy and data communication. Graphene, a unique 2D material with excellent plasmonic properties is a promising alternative to conventional noble metals in plasmonics notably due to its tunable properties. Graphene is modelled in this thesis as an infinitesimally thin current-carrying sheet in a fully vectorial finite element Galerkin framework as opposed to more conventional models where graphene is considered to be of finite thickness. A rigorous study of the behaviour of the electromagnetic field along the propagation direction in an openridge waveguide is carried out by modelling graphene as a 1D conductive scatterer which acts as a local perturbation. The scattering model is verified through a full energy balance in different geometries. The large momentum mismatch that exists between the waveguide mode and the graphene plasmon mode in a graphene-based waveguide severely alters the coupling between these two modes. To overcome this, a coupler is designed using the developed scattering field formalism. Elaborate studies of the beating phenomenon observed in the coupler are performed. The designed waveguide coupler is apt for graphene of lengths equal to or shorter than the order of the wavelength. Several studies involving the various diffraction orders of the grating coupler, waveguide thickness, etc. are conducted. The parameters of the coupler are then optimized to yield a compact and integrated graphene-based grating coupler of efficiency as high as 80% in the infrared region

The main topic of this research is modelling and design of high-speed, large-force and long life-time electromagnetic actuators based on Magnetic Shape Memory (MSM) alloys. These relatively new “smart” alloys that change shape in magnetic fields possess very promising properties such as large strain, considerable output stress and potentially very long fatigue life. However, there is still lack of a consistent design methodology for MSM-based devices which can be implemented using techniques common for engineering design. In order to bridge this gap, a modelling approach for MSM element in actuators is developed in which the complete magnetic circuit of MSM actuator is included into a single finite element (FE) model. This approach also allows accurate representation of MSM permeability change during the shape change capturing its effects on total reluctance of the magnetic circuit. Moreover, this approach allows studying the magnetic field distribution in the MSM element in single, two and multi-variant states in magnetic fields of varying strength. The modelling results show striking non-homogeneity of the magnetic field distribution, providing new insights on the magneto-mechanical behaviour of the MSM element. The modelling approach is verified through comparing the calculated MSM permeability change with previously reported results obtained by measurement. Using this modelling approach, electromagnetic analysis is conducted for eleven MSM actuators. The actuators are designed and optimised for a particular 0.1mm strain (displacement) and 10N force output for implementation in food-sorting machines. The conducted analysis also ensures robustness of the designs and stable multi-billion cycle operation. The very long lifetime is achieved through careful analysis of the magnetic circuit and the behaviour of the MSM element during operation. Finally, thermal analysis is conducted for the designed actuators in order to ensure their thermal stability. In order to overcome challenges associated with a very low operating temperature limit of the MSM element in actuators, different available cooling conditions are studied. Moreover, an energy-efficient operation cycle is developed that takes advantage of the shape memory effect of the MSM element also taking into account the pressure change in the pneumatic valve of a sorting machine. The analysis shows multiple regimes which allow thermal stability in a 300Hz pulsed excitation cycle. Implementation of the developed operating cycle also leads to the considerable increase in overall efficiency.

The boost power factor correction (PFC) circuit is a common circuit in power electronics. Through years of experience, many designers have optimized the design of these circuits for particular applications. In this study, a new design procedure is presented that guarantees optimal results for any application. The algorithm used incorporates the principles of evolution in order to find the best design. This new design technique requires a rethinking of the traditional design process. Electrical models have been developed specifically for use with the optimization tool. One of the main focuses of this work is the implementation and verification of computationally efficient thermal and electro-magnetic interference (EMI) models for the boost PFC circuit. The EMI model presented can accurately predict noise levels into the 100's of kilohertz range. The thermal models presented provide very fast predictions and they have been adjusted to account for different thermal flows within the layout. This tuning procedure results in thermal predictions within 10% of actual measurement data. In order to further reduce the amount of analysis that the optimization tool must perform, some of the converter design has been performed using traditional methods. This part of the design is discussed in detail. Additionally, a per unit analysis of EMI and thermal levels is introduced. This new analysis method allows EMI and thermal levels to be compared on the same scale thus highlighting the tradeoffs between the both behaviors.
Master of Science

La nanotechnologie est un domaine en voie d'expansion qui a attiré l'attention de la recherche en raison de ses applications potentielles illimitées. La technologie des ondes millimétriques est un autre domaine intéressant qui joue un rôle de premier plan dans le développement des systèmes de communications sans fil. La combinaison de ces deux champs de recherche avancée, donne naissance à l'innovation du Dispositif Ratchet qui est une nouvelle application qui représente un vrai défi. Ce dispositif est de taille nanométrique et son concept d'opération consiste à générer une tension DC lorsque le dispositif, basé sur le gaz d'électron bidimensionnel, est rayonné par l'énergie des micro-ondes. L'objectif de cette thèse est d'essayer d'améliorer la réponse du dispositif, ce qui ouvre de nouvelles perspectives dans la fabrication des détecteurs de champ à haute fréquence et à l'échelle nanométrique. Malheureusement, les Dispositifs Ratchet actuels, basés sur des hétérostructures de semiconducteurs, réalisés jusqu'à présent fonctionnent à basse température pour assurer une grande mobilité électronique. Cette condition nécessite l'utilisation d'un setup expérimental complexe qui a un grand impact sur la tension induite et sur la reproductibilité du phénomène Ratchet observé. Dans ce contexte, le travail effectué dans le cadre de cette thèse a abordé ce problème en deux parties. La première partie concerne l'analyse électromagnétique du setup expérimental. Ceci a été réalisé par la mise en oeuvre des simulations électromagnétiques intenses. D'autre part, différentes solutions ont été proposées afin d'optimiser le setup et ainsi améliorer la tension Ratchet produite. Outre l'étude électromagnétique, certaines mesures de modulation ont été réalisées pour tester la faisabilité du Dispositif Ratchet comme un démodulateur d'amplitude. La deuxième partie de cette thèse traite l'étude de la matière qui compose le Dispositif Ratchet. Récemment, le graphène commence à envahir le monde scientifique et technologique avec ses fascinantes propriétés électroniques, tels que sa mobilité d'électrons élevée à température ambiante, où les matériaux conventionnels sont en train de confronter des obstacles. En conséquence, l'idée de fabriquer un Dispositif Ratchet à base de graphène au lieu des hétérojonctions de semiconducteurs, a été introduite. Plusieurs modèles de conception, caractérisation et mesures RF ont été accomplis en vue d'obtenir un Dispositif Ratchet fiable approprié pour de nombreuses applications pratiques à la température ambiante, dans la gamme de fréquences micro-ondes et pourraient s'étendre à la bande térahertz
Nanotechnology is a growing field that has attracted significant research attention due to its unlimited potential applications. Millimeter wave technology is another interesting field that plays a leading role in the development of wireless communications systems. Combining these two advanced research fields together, has given rise to the innovation of the Ratchet Device which is now a new challenging application. This device has a nanoscale size and its concept of operation consists of generating a DC voltage when radiating a two-dimensional electron gas based device with microwave energy. The aim of this thesis is in trying to improve the device response and hence opening new perspectives in the fabrication of high frequency field detectors on the nanoscale level. Unfortunately, the current Ratchet Devices, based on semiconductor heterostructures, realized till now, operate at low temperatures to ensure high electron mobility. This condition necessitates the use of a complex experimental setup that has a great impact on the induced voltage and on the reproducibility of the observed Ratchet phenomenon. In this context, the work performed within the framework of this thesis has addressed this problem in two parts. The first part concerns the electromagnetic analysis of the experimental setup behavior. This has been achieved by implementing intensive full wave electromagnetic simulations. Different solutions have been proposed to optimize the setup and thus enhance the Ratchet voltage produced. In addition to the electromagnetic study, some modulation measurements have been performed to test the feasibility of the Ratchet Device as an amplitude demodulator. The second part of this thesis deals with the study of the material composing the Ratchet Device. Recently, graphene has started to invade the scientific and the technological world with its fascinating electronic properties, such as its high electron mobility at room temperature, which distinguishes it from conventional materials that typically collide with obstacles. As a result, the idea of fabricating a Ratchet Device based on graphene instead of semiconductor heterojunctions has been introduced. Several design models, characterizations and RF measurements have been performed in order to obtain a reliable Ratchet Device suitable for many practical applications at room temperature. This has been done in the microwave frequency range and can also extend to the terahertz band

Presence of cultural refuse has long posed a serious challenge to meaningful geological interpretation of near surface controlled–source electromagnetic data (CSEM). Cultural refuse, such as buried pipes, underground storage tanks, unexploded ordnance, is often highly conductive and magnetically permeable. Interpretation of the CSEM response in the presence of cultural noise requires an understanding of electromagnetic field diffusion and the effects of anomalous highly conductive and permeable structures embedded in geologic media. While many numerical techniques have been used to evaluate the response of three dimensional subsurface conductivity distributions, there is a lack of approaches for modeling the EM response incorporating variations in both subsurface conductivity σ and relative permeability μr. In this dissertation, I present a new three dimensional edge–based finite element (FE) algorithm capable of modeling the CSEM response of buried conductive and permeable targets. A coupled potential formulation for variable μ using the vector magnetic potential A and scalar electric potential V gives rise to an ungauged curl–curl equation. Using reluctivity (v=1/mu ), a new term in geophysical applications instead of traditional magnetic susceptibility, facilitates a separation of primary and secondary potentials. The resulting differential equation is solved using the finite element method (FEM) on a tetrahedral mesh with local refinement capabilities. The secondary A and V potentials are expressed in terms of the vector edge basis vectors and the scalar nodal basis functions respectively. The finite element matrix is solved using a Jacobi preconditioned QMR solver. Post processing steps to interpolate the vector potentials on the nodes of the mesh are described. The algorithm is validated against a number of analytic and multi dimensional numeric solutions. The code has been deployed to estimate the influence of magnetic permeability on the mutual coupling between multiple geological and cultural targets. Some limitations of the code with regards to speed and performance at high frequency, conductivity and permeability values have been noted. Directions for further improvement and expanding the range of applicability have been proposed.