Lightning damage resistance of unstitched carbon/epoxy laminates and a Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panel were characterized by laboratory-scale lightning strike tests and multiphysics-based lightning strike finite element (FE) models. This dissertation combines three related research topics: (1) a three-dimensional (3D) heat transfer problem, (2) lightning damage resistance assessments of carbon/epoxy laminates, and (3) lightning damage resistance of PRSEUS panel. The first project deals with a 3D analytical heat transfer problem as a solid foundation for understanding the steady-state temperature distribution in an anisotropic composite heat spreader. The second project characterizes lightning damage to unprotected carbon/epoxy laminates and laminates with either copper mesh (CM) or pitch carbon fiber paper (PCFP) protection layers subjected to standard impulse current waveforms, consistent with actual lightning waveforms, with 50, 125, and 200 kA nominal peak currents. Multiphysics-based FE models were developed to predict matrix thermal decomposition (a primary form of lightning damage) in unprotected, CM-protected, and PCFP-protected carbon/epoxy laminates. The predicted matrix decomposition domains in the damaged laminates showed good agreement with experimental results available in the literature. Both the CM and the PCFP lightning protection layers successfully mitigated lightning damage development in the underlying composites. The third project includes lightning damage characterization of a PRSEUS panel. Laboratory-scale lightning strike tests with nominal 50, 125, and 200 kA peak currents were performed at the mid-bay, stringer, frame, and frame/stringer intersection locations of the PRSEUS panel. The elliptical regions of intense local damage were elongated along the outermost lamina’s carbon fiber direction, consistent with observations from the unstitched carbon/epoxy laminates. However, the damaged PRSEUS panel exhibited unique damage features due to use of warp-knitted fabrics and through-thickness VectranTM stitches. The polyester threads used to weave the warp-knitted laminates locally confined small-scale fiber damage. This resulted in somewhat periodic and scattered small tufts of carbon fibers near the lightning attachments. Through-thickness VectranTM stitches also confined intense local damage development at the stringer and frame locations. The polyester warp-knit fabric skins and through-thickness VectranTMstitches have a significant beneficial effect on lightning damage development on a PRSEUS panel.

An optimally designed thermosiphon for power electronics cooling is developed. There exists a need for augmented grid assets to facilitate power routing and decrease line losses. Power converter augmented transformers (PCATs) are critically limited thermally. Conventional active cooling system pumps and fans will not meet the 30 year life and 99.9% reliability required for grid scale implementation. This approach seeks to develop a single-phase closed-loop thermosiphon to remove heat from power electronics at fluxes on the order of 10 - 15 W/cm2. The passive thermosiphon is inherently a coupled thermal-fluid system. A parametric model and multi-physics design optimization code will be constructed to simulate thermosiphon steady state performance. The model will utilize heat transfer and fluid dynamic correlations from literature. A particle swarm optimization technique will be implemented for its performance with discrete domain problems. Several thermosiphons will be constructed, instrumented, and tested to verify the model and reach an optimal design.

We develop a composite multiphysics model of excitation-contraction coupling for a rat ventricular myocyte under voltage clamp (VC) conditions to: (1) probe mechanisms underlying the response to Ca2+-perturbation; (2) investigate the factors influencing its electromechanical response; and (3) examine its rate-dependent behavior (particularly the force-frequency response (FFR)). Motivation for the study was to pinpoint key control variables influencing calcium-induced calcium-release (CICR) and examine its role in the context of a physiological control system regulating cytosolic Ca2+ concentration and hence the cardiac contractile response. Our cell model consists of an electrical-equivalent model for the cell membrane and a fluid-compartment model describing the flux of ionic species between the extracellular and several intracellular compartments. The model incorporates frequency-dependent calmodulin (CaM) mediated spatially heterogenous interaction of calcineurin (CaN) and Ca2+/calmodulin-dependent protein kinase-II (CaMKII) with their principal targets and accounts for rate-dependent, cyclic adenosine monophosphate (cAMP)-mediated up-regulation. We also incorporate a biophysical model for cardiac contractile mechanics to study the factors influencing force response. The model reproduces measured VC data published by several laboratories, and generates graded Ca2+-release with high Ca2+ gain by achieving negative feedback control and Ca2+-homeostasis. We examine the dependence of cellular contractile response on: (1) the amount of activator Ca2+ available; (2) the type of mechanical load applied; (3) temperature (22 to 38ºC); and (4) myofilament Ca2+ sensitivity. We demonstrate contraction-relaxation coupling over a wide range of physiological perturbations. Our model reproduces positive peak FFR observed in rat ventricular myocytes and provides quantitative insight into the underlying rate-dependence of CICR. The role of Ca2+ regulating mechanisms are examined in handling induced Ca2+-perturbations using a rigorous cellular Ca2+ balance. Extensive testing of the composite model elucidates the importance of various direct and indirect modulatory influences on the cellular twitch-response with wide agreement with measured data on all accounts. We identify cAMP-mediated stimulation, and rate-dependent CaMKII-mediated up-regulation of Ca2+-trigger current (ICaL) as the key mechanisms underlying the aforementioned positive FFR. Our model provides biophysically-based explanations of phenomena associated with CICR and provides mechanistic insights into whole-cell responses to a wide variety of testing approaches used in studies of cardiac myofilament contractility.

Le travail présenté dans cette thèse porte sur l’étude du pré-dimensionnement d’un actionneur électromécanique à entrainement direct dans une chaine de commande de vol électrique d’un hélicoptère.Le dimensionnement de cet actionneur répond à un brevet déposé par Airbus Helicopters et les éléments composant l’actionneur devront remplir les critères de sécurité des équipements embarqués des fonctions critiques. Dans un premier temps, une méthode de pré-dimensionnement d’actionneur électromécanique et plus particulièrement de machine électrique est décrite à l’aide d’un modèle analytique. Ce modèle est couplé à un algorithme d’optimisation afin de minimiser la masse tout en conservant les performances. Un prototype a fait l’objet d’une fabrication à l’échelle 1. Dans un second temps, une architecture et une méthode de calcul de l’asservissement sont définies afin d’obtenir les performances attendues par un cahier des charges en termes de précision, vitesse et stabilité. Dans le but d’améliorer le processus de dimensionnement et de prévoir le comportement dynamique de l’asservissement, des modèles multi-physiques sont développés et utilisés. Enfin, le prototype est mis en place sur un banc d’essai. Il a permis de valider le modèle de pré-dimensionnement et plus généralement de caractériser les machines électriques. Enfin, une campagne d’essai avec des cas de panne est réalisée pour mesurer et analyser les effets des pannes sur cet actionneur. / The thesis aim is the pre-design of a direct drive electromechanical actuator for Fly-By-Wire flight control of rotorcraft.The pre-design of this actuator answer to a Airbus Helicopters patent and all component must be compliant with the safety criteria of embedded system for critical function. Over a first phase, a method of electromechanical actuator’s pre-design and particularly of electrical machine is described with an analytical model. This model is linked with an optimization algorithm in order to minimize the actuator’s mass with the whole performances. A full scale prototype has been built.Over a second phase, architecture and methods for designing control are described in order to obtain the specification performances in term of precision, speed and stability. To improve the design process and the dynamic prediction of the control, multiphysics models have been developed and used.At last, the prototype is integrated on a test bench. This one allow to validate the electrical machines pre-design and more generally, to characterize the built electrical motors. A series of failure case’s tests takes place in order to analyze and measure all the actuator effect of the failure case.

En raison de ses avantages inhérents, tels que son faible coût, sa fiabilité élevée, sa capacité de fonctionnement à grande vitesse et en environnements difficiles, la machine à réluctance variable (MRV) est une solution attrayante pour l'industrie automobile. Cependant, la traction automobile est une application pour laquelle le comportement acoustique du groupe motopropulseur doit être particulièrement considéré, dans l'optique de ne pas dégrader le confort des passagers. Afin de rendre la MRV compétitive pour cette application automobile, le travail présenté se concentre sur plusieurs méthodes de contrôle cherchant à améliorer le comportement acoustique des MRV en réduisant les vibrations d'origine électromagnétique. Un modèle multi-physique électromagnétique / mécanique semi-analytique est proposé à partir de résultats de simulation numérique obtenus par la méthode des éléments finis. Ce modèle multiphysique est composé de modèles électromagnétiques et structurels, qui sont reliés par la composante radiale de la force électromagnétique. Deux méthodes de contrôle sont ensuite proposées. La première réduit la vibration en faisant varier l'angle de coupure du courant, la fréquence du la variation étant basée sur les propriétés mécaniques de la structure MRV. De plus, une fonction aléatoire uniformément distribuée est introduite pour éviter une composante fréquentielle locale de forte vibration. Une seconde méthode est basée sur le contrôle direct de la force (DFC), qui vise à obtenir une force radiale globale plus douce pour réduire les vibrations. Un adaptateur de courant de référence (RCA) est proposé pour limiter l'ondulation de couple introduite par le DFC, provoquée par l'absence de limitation de courant. Cette seconde méthode de réduction des vibrations appelée DFC & RCA est évaluée par des tests expérimentaux utilisant un prototype de MRV 8/6 afin de montrer sa pertinence. Une solution de partitionnement hardware/software est proposée pour implémenter cette méthode sur une carte FPGA utilisée en combinaison avec un microprocesseur. / Due to its inherent advantages Switched Reluctance Machine (SRM) are appealing to the automotive industry. However, automotive traction is a very noise sensitive application where the acoustic behavior of the power train may be the distinction between market success and market failure. To make SRM more competitive in the automotive application, this work will focus on the control strategy to improve the acoustic behavior of SRM by vibration reduction. A semi-analytical electromagnetic/structural multi-physics model is proposed based on the simulation results of numerical computation. This multi-physics model is composed by electromagnetic and structural models, which are connected by the radial force. Two control strategies are proposed. The first strategy to improve the acoustic behavior of SRM by vibration reduction. A semi-analytical electromagnetic/ structural multi-physics model is proposed based on the simulation results of numerical computation. This multi-physics model is composed by electromagnetic and structural models, which are connected by the radial force. Two control strategies are proposed. The first one reduces the vibration by varying the turn-off angle, the frequency of the variable signal is based on the mechanical property of switched reluctance machine. Besides, an uniformly distributed random function is introduced to avoid local high vibration component. Another one is based on the Direct Force Control (DFC), which aims to obtain a smoother total radial force to reduce the vibration. An reference current adapter (RCA) is proposed to limit the torque ripple introduced by the DFC, which is caused by the absence of the current limitation. The second vibration reduction strategy named DFC&RCA is evaluated by experimental tests using an 8/6 SRM prototype. A hardware/software partitioning solution is proposed to implement this method, where FPGA board is used combined with a Microprocessor.