This document presents a novel active magnetic levitation system. In the pursued of this endeavour different topics related with wave energy were explore. Climate change and energy security are the main motivation to pursued new options for non-fossil fuels energy generation. An overview of renewable energy and specifically of wave energy was presented. The potential for wave energy in The United Kingdom turn out to be 75 TWh/year from wave energy, 3 times more of what wind energy has produced in 2013. This means a massive impact on the energy market and emission reduction. In order to achieve this, improvements on wave energy devices have to be done. An overview of wave energy converters was covered selecting the C-Gen as the generator topology this document will base its studies. Linear generator bearings are desired to have long lifespan with long maintenance intervals. The objective is to come with an active magnetic levitation design that can replace traditional bearings augmenting the reliability of the system. Therefore magnetic bearings option have been reviewed and simulation experimentations has resulted in a novel active magnetic levitation system using an air-cored coils Halbach array acting over a levitation track. The configuration would generate bi directional repulsion forces with respect of the levitating body. Different software were used to analyse the magnetic field and forces generation. Additionally a prototype was built and tested to corroborate the results. As part of the modelling a mathematical model was explored and robust control implementation was also realised. Finally a scalability study of the device as well as a reliability analysis was done. Although the reliability studies shows an increase of ten times of the mean time to failure, the concept is not able to endure the loads acting on the generator unless the magnetic bearings became bigger than the generator and therefore economically unfeasible.

It is my hope that this thesis may serve as a guide for future students wishing to build a microscope from scratch. The design and construction of a scanning, confocal fluorescence microscope equipped with shaped microwave excitation is detailed. The use of the microscope is demonstrated by coherently manipulating single Nitrogen-Vacancy centres in diamond. Further the instrument is used to investigate a dual Halbach array magnet system.

It is my hope that this thesis may serve as a guide for future students wishing to build a microscope from scratch. The design and construction of a scanning, confocal fluorescence microscope equipped with shaped microwave excitation is detailed. The use of the microscope is demonstrated by coherently manipulating single Nitrogen-Vacancy centres in diamond. Further the instrument is used to investigate a dual Halbach array magnet system.

Ce manuscrit de thèse, intitulé " Dimensionnement d’un actionneur pour organe de pilotage à entraînement direct avec redondance passive magnétique ", s’inscrit dans un projet ANR du nom de TEMOP pour, TEchnologie Mécatronique pour Organe de Pilotage, en lien avec la société UTC Aerospace de Figeac. L’objectif de cette thèse est de développer une solution de machine électrique permettant de générer le retour d’effort actif d’un mini-manche latéral d’aéronef, dans le but d’améliorer les sensations haptiques des pilotes. Cette machine doit être assez performantes pour générer des efforts massiques importants, tout en tenant dans un encombrement réduit et en limitant l’échauffement. Un cahier des charges précis rédigé par l’industriel donne les contraintes à respecter et impose une redondance triplex sur chaque axe de tangage et de roulis. Nous avons opté pour une solution comportant un duplex actif associé à un simplex passif. Sur chaque axe, deux machines électriques actives seront montées en parallèle et une solution à retour d’effort passif magnétique a été développée. Pour ce faire, nous avons divisé notre thèse en deux parties distinctes. La première partie du manuscrit traite du dimensionnement de la machine active appelée DARM pour Double Airgap Rotative Machine. Il s’agit d’une machine synchrone à aimants permanents en configuration Halbach, comportant deux entrefers et à débattement limité. La stratégie de dimensionnement est basée sur une optimisation locale et analytique sous contraintes non-linéaires. La première partie développe les contraintes sous forme analytiques. Puis, un modèle magnétique est créé de manière à connaître le couple que la structure développe en fonction des différentes variables d’optimisation. Ce modèle a été validé par éléments finis grâce aux logiciels ANSYS et JMAG. Une optimisation permet d’aboutir aux dimensions de l’actionneur satisfaisant au cahier des charges. Puis, dans le but de vérifier les températures atteintes dans chaque zones, un modèle thermique global, utilisant des résistances thermiques équivalentes a été établi et validé par simulations. Ainsi, on vérifie que la structure optimisée n’atteint pas des températures critiques. Enfin, nous validerons nos calculs par des mesures expérimentales. Un chapitre du manuscrit est dédié au dimensionnement de la partie passive. Nous avons imaginé un système innovant qui couple une fonction de ressort et d’amortisseur. La fonction de ressort s’appuie sur le phénomène de répulsion entre deux aimants permanents, alors que la fonction d’amortisseur est créée par un système de freinage passif par courants de Foucault. La stratégie de dimensionnement est divisée en deux partie. Les dimensions du système de ressort sont préalablement choisies grâce à une optimisation paramétrique locale couplant le logiciel MATLAB au logiciel de simulations par éléments finis FEMM. Lorsque ces dimensions sont fixées, le système d’amortisseur est dimensionné par une optimisation locale analytique où la fonction objectif a pour vocation de maximiser le couple de freinage. Nous nous sommes donc entachés à développer un modèle qui permet de calculer ce couple. Sur cette base, un prototype a été élaboré, sur lequel des mesures expérimentales ont permis de valider le concept. / This thesis manuscript titles "Dimensionnement d’un actionneur pour organe de pilotage à entraînement direct avec redondance passive magnétique ", which means " Design of an active flight control direct drive actuator with a passive magnetic redundancy ", is seen against an ANR project named TEMOP for, " TEchnologie Mécatronique pour Organe de Pilotage ", and is in connection with the UTC Aerospace industry in Figeac in France. The objective of this thesis is to develop a solution of electrical machine, which permits to create an active force feed-back for an aircraft side-stick, in order to improve the haptic sensations of the pilot. This machine have to be enough powerful to create high forces per unit of mass. We also need to respect the overall dimensions and to decrease the heating as much as possible. A precise set of specifications, redacted by UTC Aerospace, gives the constraints and impose to have a triple redundancy on each axis of pitch and roll. We chose to develop a duplex active redundancy with an added simplex passive actuator. Our full system have 6 machines : 4 are actives and 2 are passives. Our thesis is divided in two main parts. The first part of the manuscript deals with the design of the active machine called DARM for " Double Airgap Rotative Machine ". It is a synchronous permanent magnet machine, with a Halbach pattern, with two airgaps and a non-entire arc. The design method is based on an analytical optimization process under a set of non-linear constraints. Each of them are traduced mathematically and an electromagnetic 2D model is developed, in order to give the theoretical torque reached, in function of the variables of the problem. This model has been validated with FEM simulations with the ANSYS and JMAG softwares. An optimization is realized to give the dimensions of the DARM. Then, in order to verify the temperatures, we developed a global thermal model, based on an equivalent electric circuit. It permits to verify that the temperatures reached in the structure, are under the limits given by the set of specifications. This model is verified by FEM simulations using ANSYS. Finally, we will validate our models with experimental measures. However, a chapter is dedicated to the design of the passive actuator. We imagined an innovative system, which have two different utilities. The first one is a function of spring, the second is a function of shock absorber. The spring is based on the repulsion phenomenon between two magnets. The shock absorber is created with a system of Eddy currents breaker. The design method is divided in two. In the first time, we design the spring with a parametric optimization using the FEMM software coupled to the MATLAB software. When the dimensions of the spring are known, we design the shock absorber with an analytical optimization process which use an electromagnetic torque model developed in this part. A prototype has been built in order to verify the models.

The magnetic field analysis based on the wavelet transform is performed. The Halbach array magnetic field analysis has been studied using many methods such as magnetic scalar potential, magnetic vector potential, Fourier analysis and Finite Element Methods. But these analyses cannot identify a transient oscillation at the beginning stage of levitation. The wavelet transform is used for analyzing the transient oscillatory response of an EDS Maglev system. The proposed scheme explains the under-damped dynamics that results from the cradle's dynamic response to the irregular distribution of the magnetic field. It suggests this EDS Maglev system that responds to a vertical repulsive force could be subject to such instability at the beginning stage of a low levitation height. The proposed method is useful in analyzing instabilities at the beginning stage of levitation height. A controller for the EDS maglev system with the Halbach array magnet is designed for the beginning stage of levitation and after reaching the defined levitation height. To design a controller for the EDS system, two different stages are suggested. Before the object reaches a stable position and after it has reached a stable position. A stable position can be referred to as a nominal height. The former is the stage I and the latter is the stage II. At the stage I, to achieve a nominal height the robust controller is investigated. At the stage II, both translational and rotational motions are considered for the control design. To maintain system stability, damping control as well as LQR control are performed. The proposed method is helpful to understand system dynamics and achieve system stability.

This thesis presents a novel study on Second Generation High Temperature Superconductors, which covers their electromagnetic characteristics and AC loss analysis. Lorentz Force Electrical Impedance Tomography (LFEIT) is one of the most promising hybrid diagnostic scanners with burgeoning potential for biological imaging, particularly in the detection of cancer and internal haemorrhages. The author tried a novel combination of superconducting magnets together with the LFEIT system. The reason is that superconducting magnets can generate a magnetic field with high intensity and homogeneity, which could significantly enhance the electrical signal induced from a sample, thus improving the Signal-to-Noise Ratio (SNR). The author developed four magnet designs for the LEFIT system using the Finite Element Method (FEM) package, COMSOL Multiphysics, and found that a Superconducting Halbach Array magnet can achieve all the requirements (magnetic field properties, geometry, portability, etc.) for the LFEIT system. The optimization study of the superconducting Halbach Array magnet has been carried out on the FEM platform of COMSOL Multiphysics, with 2D models using H-formulation based on B-dependent critical current density and bulk approximation. Optimization focused on the location of the coils, as well as the geometry and number of coils on the premise of maintaining the total amount of superconducting material used in the design. The optimization results showed that the Halbach Array configuration based superconducting magnet is able to generate a magnetic field with an intensity of over 1 Tesla and improved homogeneity. In order to efficiently predict the optimization performance, mathematical formulas were developed for these optimization parameters to determine the intensity and homogeneity of the magnetic field. The mathematical model for the LFEIT system was built based on the theory of the magneto-acousto-electric effect. Then the basic imaging of the electrical signal was developed using Matlab. The magnetic field properties of the magnet design were imported into the LFEIT model. The LFEIT model simulated two samples located in three different magnetic fields with varying magnetic strength and homogeneity. Even if there are no actual alternating currents involved in the DC superconducting magnets mentioned above, they have power dissipation during normal operation (e.g. magnet ramping) and under different background fields. This problem generally goes under the category of “AC loss”. Therefore, the AC loss characteristics of HTS tapes and coils are still fundamentally important for HTS magnet designs, even if they are normally operating in DC conditions. This thesis starts with the AC loss study of HTS tapes. The investigation and comparison of AC losses on Surround Copper Stabilizer (SCS) Tape and Stabilizer-free (SF) Tape have been carried out, which includes AC loss measurement using the electrical method, as well as the real geometry and multi-layer HTS tape simulation using the 2D H formulation by COMSOL Multiphysics. Hysteresis AC losses in the superconducting layer, and eddy current AC losses in the copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from the simulation, using 3 cases of different AC frequency: 10 Hz, 100 Hz, and 1000 Hz. The frequency dependence of AC losses from Stabilizer free Tape and Copper Stabilizer Tape were compared and analysed. A comprehensive AC loss study of a circular HTS coil has been fulfilled. The AC losses from a circular double pancake coil were measured using the electrical method. A 2D axisymmetric H-formulation model using FEM package COMSOL has been established, which was able to make consistency with the real circular coil used in the experiment. To model a circular HTS coil, a 2D axisymmetric model provided better accuracy than a general 2D model, and was also more efficient than a 3D model. Three scenarios were analysed: (1) AC transport current and DC magnetic field, (2) DC transport current and AC magnetic field, (3) AC transport current and AC magnetic field. The angular dependence analysis on the coil under the magnetic field with the different orientation angle  was carried out for all three scenarios. For scenario (3), the effect of the relative phase difference ∆ between the AC current and the AC field on the total AC loss of the coil was investigated. To summarise, a current/field/angle/phase dependent AC loss (I, B, , ∆) study of circular HTS coil has been carried out, which could potentially benefit the future design and research of HTS AC systems. The AC losses of horizontally parallel HTS tapes have been investigated. The AC losses of the middle and end tape of three parallel tapes have been measured using the electrical method, and compared to those of an individual isolated tape. The effect of the interaction between tapes on AC losses has been analysed, and compared with finite element method (FEM) simulations using the 2D H formulation implemented in COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil were simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrated that HTS parallel tapes could be potentially used in wireless power transfer systems, which could have lower total AC losses than conventional HTS coils. By using FEM simulations, cases of increasing number of parallel tapes was considered, and the normalised ratio between the total average AC losses per tape and the AC losses of an individual single tape have been calculated for different gap distances. A new parameter is proposed, Ns, a turning point the for number of tapes, to divide Stage 1 and Stage 2 for the AC loss study of horizontally parallel tapes. For Stage 1, N < Ns, the total average losses per tape increased with the increasing number of tapes. For Stage 2, N > Ns, the total average losses per tape started to decrease with the increasing number of tapes. The analysis demonstrates that horizontally parallel HTS tapes could be potentially used in superconducting devices like HTS transformers, which could retain or even reduce the total average AC losses per tape with large numbers of parallel tapes.

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