Accurate linear and nonlinear models for devices and components are essential for successful RF/microwave computer aided engineering (CAE). The modeling techniques can be categorized in different levels based on the abstraction of the model as well as the application of the models at various design phases. This dissertation deals with behavioral modeling techniques for nonlinear RF components, especially amplifiers. There is an increasing demand for accurate behavioral models of RF and microwave components, or integrated circuit (IC) blocks used in wireless system designs. Accurate behavioral models help designers evaluate and select the appropriate components at simulation phase, thereby cutting development cost. However, there isnt a practical (or flexible) solution for accurate and effective behavioral model generation. This dissertation tries to tackle this problem. Power amplifiers and devices are the main components studied in this dissertation. The primary focus is on the characterization of the loadpull performance of power amplifiers and devices. Major contributions of this dissertation include development of advanced loadpull measurement procedures, large-signal load-aware behavioral model, and a load-aware behavioral model with memory-effect capabilities. There are two advanced loadpull measurements documented in this dissertation: the AM-PM loadpull measurement and the digital demodulation loadpull measurement. These two measurements may have been used internally by some research groups, however, according to the best knowledge of the author, they havent received much attention in the literature. This is the first published work on these two topics. It is shown in this work that the AM-PM performance can be strongly dependent on the load conditions. This property provides important information about the nonlinearities of power amplifiers and is used herein to create better behavioral models. This newly developed digital demodulation loadpull measurement procedure enables system designers to evaluate power amplifiers directly against digital communication system parameters such as error vector magnitude (EVM). Two example measurements are given to demonstrate the measurement system setup and the correlations between traditional nonlinear figure-of-merits and system metrics. A new behavioral modeling technique / procedure is developed based on loadpull AM-AM and AM-PM measurements. The large-signal scattering function theory is applied in the technique to formulate the model. The created model is able to automatically detect the load impedance and generate corresponding nonlinear properties. Three example models are presented to demonstrate the capability of this technique to predict accurately the output power contours, 50 ohm large-signal S21, and 3rd order intermodulation products (through additional file-based model). Finally, a modeling technique is demonstrated to enable predicting the linear memory effect within a varying load condition. The nonlinear block used in the traditional two-box model structure is replaced with the large-signal loadpull model mentioned above. By adding this new feature, the resulting model is able to predict the load-related AM-AM and AM-PM properties, which will improve the accuracy of ACPR prediction.

This thesis has sought to provide another look at RF interference at the fundamental level. While previous interference control and regulation methods have existed in the literature, they were more focused on preventing the interference from happening. On the contrary, we have taken a different approach of correcting the interference once it has happened. This allows the transmitters to be more nonlinear, passive filter design to be eased, and receivers to be aware of interference problems. Under this unifying theme of building intelligent radios where receivers are more cognizant of the transmission environment, we have presented a number of architectures.

La chirurgie minimalement invasive est aujourd’hui une thématique de recherche particulièrement active. Un traitement thérapeutique ciblé et la possibilité d’établir un diagnostic précis grâce à l’utilisation de systèmes miniaturisés peuvent considérablement améliorer de nombreuses pratiques médicales. Le recours à des microrobots actionnés à distance et naviguant dans le système cardiovasculaire ouvre de nouvelles perspectives. L’objectif de cette thèse est de proposer un socle théorique solide concernant i) la modélisation d’un microrobot naviguant dans le système cardiovasculaire, ii) l’élaboration de lois de commande et d’observateurs assurant un bon suivi de trajectoire depuis la zone d’injection jusqu’à une zone cible. La modélisation du système fait intervenir de nombreuses forces : forces hydrodynamiques, forces surfaciques (électrostatique, van der Waals, stériques), forces de contact et poids apparent du microrobot. Ce microrobot est contrôlé dans le système cardiovasculaire par l’application de champs ou de gradients de champ magnétique selon le design du microrobot. La prise en compte de l’ensemble des forces aboutit à une représentation d’état sous la forme d’un système non-linéaire affine en la commande avec dérive comportant de nombreux paramètres physiologiques incertains. Une trajectoire de référence optimisée est déduite du modèle. L’approche de commande adoptée est établie à partir de critères de stabilité du système. Le système étant non-linéaire, une commande de type Lyapunov stabilisante est développée suivant une approche de type backstepping. L’estimation de certains paramètres physiologiques est rendue possible par une commande de type backstepping adaptatif. Un observateur grand gain reconstruit l’état complet du système nécessaire au calcul de la commande. La stabilité et la robustesse de l’ensemble sont établies au travers de nombreuses simulations en présence de bruits de mesure et d’erreurs paramétriques. / Minimally invasive medical procedures are currently an active research aera. A drug targeted therapy and the possibility of establishing an accurate diagnosis through the use of miniaturized systems can greatly improve many medical practices. The use of untethered microrobots navigating in the cardiovascular system opens new perspectives. The objective of this PhD work is to provide a theoretical approach on i) the modeling of a microrobot navigating in the cardiovascular system, ii) the development of control laws and observers to ensure a fine tracking from the injection to a target area. Modeling such as system involves many forces : hydrodynamic forces, surface forces (electrostatic, van derWaals, steric), contact forces and apparent weight of the microrobot. This microrobot is controlled in the cardiovascular system by the application of magnetic fields or magnetic field gradients according to the design of the microrobot. The consideration of all the forces leads to a state representation in the form of a nonlinear system with many physiological uncertain parameters, but gives us sufficient informations to plan an optimal trajectory. The control approach is established based on stability consideration. A Lyapunov-stabilizing control is then developed using a backstepping approach. An adaptive backstepping control law estimates some physiological parameters. A high gain observer reconstructs the full state of the system required for implementing the control approach. Robustness and stability of the controller with respect to noise measurement, parameters variations and uncertainties are illustrated by simulations.

L'objectif de cette thèse est d'analyser et de caractériser le lien entre les mouvements du sol et la réponse des bâtiments. En particulier, on s'intéresse à réduire les incertitudes qui entrent en jeu dans les méthodes de vulnérabilité, afin d'estimer plus précisément la vulnérabilité des structures au risque sismique. Pour ce faire, cette thèse est basée sur l'utilisation de données enregistrées au sein de bâtiments. Les enregistrements de vibrations ambiantes et de séismes de faibles amplitudes au sein de bâtiments permettent de caractériser le comportement élastique de ces structures. Des modèles peuvent ensuite être définis afin d'étudier les différentes composantes de la variabilité présente au sein des courbes de fragilité. On s'intéresse dans un premier temps au premier niveau de dommage, au-delà duquel les caractéristiques élastiques des bâtiments sont modifiées et les modèles définis ne sont plus valables. Des enregistrements de séismes ayant eu lieu depuis le début des années 1970 dans des bâtiments californiens sont ensuite utilisés. A partir de ces données, on a pu mettre en évidence des relations entre le déplacement au sein des structures et des paramètres décrivant la nocivité des signaux sismiques. Suivant l'indicateur utilisé pour représenter la nocivité des séismes, la réponse des bâtiments peut être estimée plus ou moins précisément. Notamment, les indicateurs faisant intervenir les paramètres dynamiques des bâtiments sont davantage liés avec la réponse des structures, représentée par son déplacement inter-étage moyen. La variabilité de la réponse des bâtiments peut être améliorée en regroupant les bâtiments par typologies (définies suivant leur matériau principal de construction et leur hauteur). En apportant davantage d'informations sur les structures, on peut ainsi diminuer la composante épistémique de la variabilité. De plus, en combinant des indicateurs de nocivité, on peut améliorer la précision pour la prédiction de la réponse de la structure. Une forme fonctionnelle est ainsi proposée afin d'estimer le déplacement inter-étage moyen au sein des structures, pour plusieurs typologies de bâtiments, à partir de quatre indicateurs de nocivité. Cette forme fonctionnelle est utilisée pour établir des courbes de fragilité et peut également être utilisée afin de donner une première estimation des dommages à la suite d'un séisme, en comparant les valeurs de déformations inter-étages avec des valeurs de référence (FEMA, 2003). Enfin, une méthode hybride est proposée pour la construction de courbes de fragilité, faisant intervenir un modèle de comportement non linéaire. Les paramètres de ce modèle sont définis de telle sorte que la réponse du modèle s'ajuste aux enregistrements de séismes effectués dans les bâtiments. Ce modèle est ensuite utilisé pour évaluer les composantes d'incertitudes et pour construire des courbes de fragilité pour tous les niveaux de dommages. / This PhD thesis is focused on the correlation between ground motion and the buildings response. In particular, we interested in reducing the uncertainties that occur in vulnerability methods in order to assess more precisely the seismic vulnerability of existing structures. In order to do this, this thesis is based on the use of data recorded within buildings. Records of ambient vibrations and low amplitude earthquakes within buildings are used to characterize the elastic behaviour of these structures. Linear models can then be defined in order to study the various components of the variability of the fragility curves, for the first damage level. Earthquake that have occurred since the 1970s have been recorded within Californian buildings. From these data, we focused on the relationship between the building response and parameters describing the noxiousness of ground motion. Depending on the indicator used to represent the noxiousness of earthquakes, the building response can be estimated more or less accurately. In particular, indicators involving the dynamic parameters of the buildings are more related with the response of structures, which is represented by its averaged inter-story drift. Grouping buildings by typologies (defined according to their main material of construction and their height) can improve the variability in the response of buildings. Indeed, by providing more information on the structure, we can reduce the epistemic component of variability. In addition, by combining noxiousness parameters, the accuracy in the prediction of the building response can be improved. A functional form is thus proposed to estimate the averaged inter-story drift within the structures, for several typologies of buildings. This functional form is then used to assess fragility curves and can also be used to get an estimate of damage after an earthquake, by comparing the values of inter-story drift from given by the functional form with reference values (FEMA, 2003). Finally, a hybrid method is proposed for the construction of fragility curves, involving a nonlinear model. The parameters of this model are defined so that the response of the model fits the earthquake recordings, which were made within buildings. This model is then used to evaluate the components of variability and to build fragility curves for all damage levels.

Dans l’environnement concurrentiel d’aujourd’hui, la mondialisation des marchés et les enjeux socio-écologiques du développement durable représentent des défis majeurs pour l’industrie automobile. Afin de relever ces défis, les entreprises doivent investir dans des outils de développent plus performants. Pour améliorer la performance d’un moteur thermique en termes de consommation et d’émissions une compréhension enrichie de la boucle d’air autour du moteur et de l’interaction entre ses composants est indispensable Cette thèse suit deux axes de recherche dans ce contexte. Dans un premier temps, les problèmes liés à la modélisation d’une boucle d’air globale sont traités. En particulier, sont modélisés le débit d’air entre les différents sous-systèmes, la combustion en fonction du degré vilebrequin, la pulsation du débit et de la pression et l’estimation de la force aérodynamique sur les vannes des turbocompresseurs à géométrie variable (TGV). Cette étude de modélisation détaillée à été utilisée pour mettre en place un simulateur de la boucle d’air, qui prend en compte ces interactions et qui peut prédire l’influence des sous-systèmes sur la boucle globale. En suite, l’effort de notre recherche a été consacré à la modélisation des actionneurs mécatroniques de la boucle d’air et de leur comportement non linéaire dû au frottement, aux variations de la température, etc. Un modèle dynamique non linéaire à été développé et intégré dans le simulateur. Ce modèle peut être adapté aux plusieurs types d’actionneurs commerciaux. Le simulateur complet à été implémenté sous AMESim pour les modèles du moteur et de la boucle d’air, et sous Simulink pour le contrôle. Les modèles ont été paramétrées selon les spécifications d’un moteur commercial et le simulateur à été validé expérimentalement. Finalement, des lois de commande robustes ont été étudiées pour le contrôle en position (contrôle locale) des actionneurs. Un contrôleur adaptatif à été développé pour garantir la performance des actionneurs malgré des changements dans le frottement, ainsi que dans la charge externe. La performance de toutes les méthodes étudiées, a été validée expérimentalement. / Today’s globally competitive market and its associated environmental and social issues of sustainable development are major challenges for the automobile industry. To meet them, the industry needs to invest in high performance development tools. For improving engine performance in terms of consumption and emission, the interactions between the subsystems of the engine air-path need to be understood. This thesis followed two major axes of research in this context. First, the problems related to the modeling of the global air-path system were studied, which include the airflow characteristics between the different subsystems of the air-path, high frequency combustion modeling and pulsating airflow, and estimation of the exhaust aerodynamic force on the vanes of variable geometry turbochargers (VGT). The detailed modeling study was used for developing an engine air-path simulator, which takes into account these interactions and predicts the influence of subsystems on the global air-path. The second axis of research was focused on modeling of mechatronic actuators of the air-path, taking into account their nonlinear behavior due to friction and changes in operating conditions. A generic nonlinear dynamic model was developed and included in the simulator. This model can be adapted to most commercial actuators. The complete simulator has been implemented using AMESim for engine and air-path modeling, and Simulink for control. It has been parameterized according to the specifications of a commercial diesel engine and validated against experimental data. Finally, robust local controllers were studied for actuator position control, aimed at guaranteeing the performance of the actuators under parametric uncertainty and external disturbances. An advanced controller was developed, which adapts to changes in friction characteristics of the actuator and external load changes. The performance of all controllers has been demonstrated experimentally.

Made available in DSpace on 2014-12-17T14:55:56Z (GMT). No. of bitstreams: 1 MarcioGP.pdf: 1534925 bytes, checksum: d1c777b1e76b23d509caeb3258a0aa97 (MD5) Previous issue date: 2006-06-19 / This dissertation contributes for the development of methodologies through feed forward artificial neural networks for microwave and optical devices modeling. A bibliographical revision on the applications of neuro-computational techniques in the areas of microwave/optical engineering was carried through. Characteristics of networks MLP, RBF and SFNN, as well as the strategies of supervised learning had been presented. Adjustment expressions of the networks free parameters above cited had been deduced from the gradient method. Conventional method EM-ANN was applied in the modeling of microwave passive devices and optical amplifiers. For this, they had been proposals modular configurations based in networks SFNN and RBF/MLP objectifying a bigger capacity of models generalization. As for the training of the used networks, the Rprop algorithm was applied. All the algorithms used in the attainment of the models of this dissertation had been implemented in Matlab / Esta disserta??o contribui para o desenvolvimento de metodologias atrav?s de redes neurais artificiais de alimenta??o direta para a modelagem de dispositivos de microondas e ?pticos. Uma revis?o bibliogr?fica sobre as aplica??es de t?cnicas neuro-computacionais na ?reas de engenharia de microondas e ?ptica foi realizada. As caracter?sticas das redes MLP, RBF e SFNN, bem como as estrat?gias de aprendizado supervisionado foram apresentadas. As express?es de ajuste dos par?metros livres das redes acima citadas foram deduzidas a partir do m?todo do gradiente. O m?todo convencional EM-ANN foi aplicado na modelagem de dispositivos passivos de microondas e amplificadores ?pticos. Para isto, foram propostas configura??es modulares baseadas em redes SFNN e RBF/MLP objetivando uma maior capacidade de generaliza??o dos modelos. No que se refere ao treinamento das redes utilizadas, o algoritmo Rprop foi aplicado. Todos os algoritmos utilizados na obten??o dos modelos desta disserta??o foram implementados em Matlab

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-06-21T20:19:46Z No. of bitstreams: 2 Dissertação - Lázaro Antônio da Fonseca Júnior - 2016.pdf: 4302435 bytes, checksum: d5e83d077c918367e41f439d3bab359e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Cláudia Bueno (claudiamoura18@gmail.com) on 2017-07-07T19:54:39Z (GMT) No. of bitstreams: 2 Dissertação - Lázaro Antônio da Fonseca Júnior - 2016.pdf: 4302435 bytes, checksum: d5e83d077c918367e41f439d3bab359e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-07T19:54:39Z (GMT). No. of bitstreams: 2 Dissertação - Lázaro Antônio da Fonseca Júnior - 2016.pdf: 4302435 bytes, checksum: d5e83d077c918367e41f439d3bab359e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Currently, the structures are increasingly diverse and complex. In many cases, these structures are model by numerical approximations methods because, due to its complexity, the analytical model does not exist or is not feasible. The finite element method is a numerical approximation methods most used. Thus, the model generated by the finite element method is in most cases considerably too large, and the time taken to perform computer simulations is high. In this context, models reduction methods, it has been studied to meet the need of accurate results while maintaining the dynamic properties of the structure with less processing time. A comparative study of three reduction methods will be presented, the Improved Reduced System (IRS) and the Iterative Improved Reduced System method (IIRS). The third reduction method, it is an enrichment of the IRS method proposed by the author, which provided great improvement in time savings during simulations. This method was called Improved Reduced System Enriched (IRSE). Such reduction methods were applied in non-linear systems with non-localized linear and geometric nonlinearity due to large displacements. Keywords: Finite element method, nonlinear modeling, not linearity located and geometric, reduced models. / Atualmente, as estruturas estão cada vez mais diversificadas e complexas. Em muitos casos, essas estruturas são modeladas por métodos de aproximações numéricas, pois, devido à sua complexidade, o modelo analítico não existe ou não é viável. O método dos elementos finitos é um dos métodos de aproximação numérica mais utilizado. Assim, o modelo gerado pelo método dos elementos finitos é na maioria dos casos consideravelmente muito grande, e o tempo gasto para realizar simulações computacionais é alto. Neste contexto, os métodos de redução de modelos, tem sido estudados a fim de satisfazer a necessidade entre obter resultados precisos, mantendo as propriedades dinâmicas da estrutura, com menor tempo de processamento. Um estudo comparativo entre três métodos de redução será apresentado, a saber Improved Reduced System (IRS) e o método Iterative Improved Reduced System (IIRS). O terceiro método de redução, trata-se de um enriquecimento do método IRS, proposto pelo autor, que proporcionou grande melhora na economia de tempo durante as simulações. Esse método foi chamado Improved Reduced System Enriched (IRSE). Tais métodos de redução, foram aplicados em sistemas não lineares, com não linearidade localizada e não linearidade geométrica, devido a grandes deslocamentos.

The first objective of this Dissertation is to present a methodology to calculate analytically the mode shapes and corresponding natural frequencies and determine critical buckling loads of mechanically coupled microbeam resonators with a focus on micromechanical filters. The second objective is to adopt a nonlinear approach to build a reduced-order model and obtain closed-form expressions for the response of the filter to a primary resonance. The third objective is to investigate the feasibility of employing subharmonic excitation to build bandpass filters consisting of either two sets of two beams coupled mechanically or two sets of clamped-clamped beams. Throughout this Dissertation, we treat filters as distributed-parameter systems. In the first part of the Dissertation, we demonstrate the methodology by considering a mechanical filter composed of two beams coupled by a weak beam. We solve a boundary-value problem (BVP) composed of five equations and twenty boundary conditions for the natural frequencies and mode shapes. We reduce the problem to a set of three linear homogeneous algebraic equations for three constants and the frequencies in order to obtain a deeper insight into the relation between the design parameters and the performance metrics. In an approach similar to the vibration problem, we solve the buckling problem to study the effect of the residual stress on the static stability of the structure. To achieve the second objective, we develop a reduced-order model for the filter by writing the Lagrangian and applying the Galerkin procedure using its analytically calculated linear global mode shapes as basis functions. The resulting model accounts for the geometric and electric nonlinearities and the coupling between them. Using the method of multiple scales, we obtain closed-form expressions for the deflection and the electric current in the case of one-to-one internal and primary resonances. The closed-form solution shows that there are three possible operating ranges, depending on the DC voltage. For low DC voltages, the effective nonlinearity is positive and the filter behavior is hardening, whereas for large DC voltages, the effective nonlinearity is negative and the filter behavior is softening. We found that, when mismatched DC voltages are applied to the primary resonators, the first mode is localized in the softer resonator and the second mode is localized in the stiffer resonator. We note that the excitation amplitude can be increased without worrying about the appearance of multivaluedness when operating the filter in the near-linear range. The upper bound in this case is the occurrence of the dynamic pull-in instability. In the softening and hardening operating ranges, the adverse effects of the multi-valued response, such as hysteresis and jumps, limit the range of the input signal. To achieve the third objective, we propose a filtration technique based on subharmonic resonance excitation to attain bandpass filters with ideal stopband rejection and sharp rolloff. The filtration mechanism depends on tuning two oscillators such that one operates in the softening range and the other operates in the hardening range. Hardware and logic schemes are necessary to realize the proposed filter. We derive a reduced-order model using a methodology similar to that used in the primary excitation case, but with all necessary changes to account for the subharmonic resonance of order one-half. We observe that some manipulations are essential for a structure of two beams coupled by a weak spring to be suitable for filtration. To avoid these complications, we use a pair of single clamped-clamped beams to achieve our goal. Using a model derived by attacking directly the distributed-parameters problem, we suggest design guidelines to select beams that are potential candidates for building a bandpass filter. We demonstrate the proposed mechanism using an example. / Ph. D.

L'émergence des transformateurs piézoélectriques coïncident avec le développement dans les années 1950 des céramiques ferroélectriques appartenant à la famille cristalline des pérovskites qui n'ont cessé de s'améliorer depuis. Outre la compacité dont bénéficie ces structures, les transformateurs piézoélectriques offrent des performances remarquables en terme de gain en tension et rendement utiles pour des applications nécessitant une adaptation de tension ou une isolation galvanique, parfaitement dédiés aux applications de faibles puissances à haut rendement. Toutefois, les transformateurs piézoélectriques peuvent être déviés de leurs applications premières. En effet, la dernière décennie a été marquée par l'apparition de générateur de plasma par effet piézoélectrique utilisant principalement des architectures de type transformateur. Pourtant, si quelques applications usuelles illustrent parfaitement cette interaction, la compréhension des phénomènes physiques qui en sont à l'origine reste à approfondir. L'objectif de cette thèse est d'en expliquer les fondements par une approche méthodique. Ce travail s'articule autour de plusieurs étapes comprenant la mise en oeuvre d'une méthode systématique de la modélisation analytique d'un transformateur piézoélectrique, de l'étude de la carte de champ produit par un transformateur ainsi qu'une étude expérimentale vue des bornes en guise de premières investigations. La modélisation analytique est basée sur l'exploitation du Principe de Moindre Action (PMA). A partir de la théorie linéaire de la piézoélectricité, un modèle général applicable à toutes les géométries de transformateur, exploitant des modes de couplage piézoélectrique multiples, est proposé. Son caractère multimodal est par ailleurs mis en exergue. Cette modélisation est appliquée à une structure classique de transformateur piézoélectrique de type Rosen et les résultats obtenus sont validés d'une part par une identification numérique, issue d'un logiciel de calcul par éléments finis, et d'autre part par une caractérisation expérimentale. La modélisation analytique précédente ne tient pas compte dans sa mise en oeuvre de l'influence de l'environnement dans lequel évolue le transformateur piézoélectrique. Afin de caractériser le potentiel électrique produit, un modèle numérique 2D du champ électrique environnant est proposé selon la méthode des différences finies. Ce modèle est basé sur une extension du modèle analytique précédemment développé incluant les pertes mécaniques afin de quantifier le potentiel électrique de surface. Même si l'influence du plasma est négligée en première approximation, la modélisation permet de mettre en lumière les zones de fort champ correspondant aux zones de décharges luminescentes observées expérimentalement. Finalement, afin de valider le concept de générateur de plasma piézoélectrique, une caractérisation vue des bornes du transformateur piézoélectrique de type Rosen a été entreprise. Une étude systématique du déclenchement de la décharge plasma en fonction du niveau de tension et de la pression environnante a été menée. Cette part expérimentale de l'étude constitue une approche pionnière pour qualifier le comportement électromécanique du transformateur et a ainsi permis de mettre en évidence des comportements non linéaires issus de ce mode de fonctionnement atypique qu'est la génération de décharges de surface par effet piézoélectrique. / The emergence of piezoelectric transformers coincides with the development in the 1950s of ferroelectric ceramics belonging to the perovskites crystalline family. In addition to providing small size and weight, piezoelectric transformers offer outstanding performances in terms of galvanic insulation, voltage ratio and efficiency. Furthermore, compared with conventional electromagnetic transformers, piezoelectric transformers are free from electromagnetic interference. They are consequently more suitable for low power and high efficiency applications for small embedded systems. However, piezoelectric transformers can be deviated from their initial applications. Indeed, the emergence of plasma generator by piezoelectric effect, using mainly piezoelectric transformers, made its mark on the last decade. Nevertheless, if a few typical applications perfectly exemplify this interaction, the understanding of instigated physical phenomena remains to go into detail. The aim of this thesis is to explain the fundaments by a methodical approach. This work is based on several steps including the implementation of piezoelectric transformer analytical modeling, the study of the electrical field generated by a piezoelectric transformer and a first experimental investigation from piezoelectric transformer terminals. The analytical modeling is based on the utilization of the least action principle. From linear piezoelectric theory, a general model applicable to all transformer geometries, using multiple piezoelectric coupling modes, is put forward. Its multimodal characteristic is in addition underlined. This modeling is applied to a classical Rosen type transformer and the obtained results are confirmed on one hand by a numerical identication, and on the other hand by an experimental characterization. The previous analytical modeling does not take into account in its application the influence of the environment in which the piezoelectric transformer evolves. In order to qualify the produced electrical potential, a 2D numerical model of surrounding electrical field is put forward according to nite difference method. This model is based on the extension of previously developed analytical model including mechanical losses in order to quantify the surfacic electrical potential. Even if plasma influence is ignored in first approximation, the modeling allows to highlight high electrical field areas matching glow discharges areas experimentally observed. Finally, in order to validate the concept of piezoelectric plasma generator, a characterization from Rosen type piezoelectric transformer terminals has been undertaken. A systematic study of plasma discharge ignition in function of the input voltage level and the surrounding pressure has been carried out. This experimental part of the study constitutes a pioneering approach in order to qualify transformer electromechanical behavior. It has consequently allowed to give rise to nonlinear behaviors from untypical operation mode which is the surfacic discharge generation by piezoelectric effect.

The nonlinear simulation model of an unmanned aerial vehicle (UAV) in MATLAB&reg / /Simulink&reg / environment is developed by taking into consideration all the possible major system components such as actuators, gravity, engine, atmosphere, wind-turbulence models, as well as the aerodynamics components in the 6 DOF equations of motion. Trim and linearization of the developed nonlinear model are accomplished and various related analyses are carried out. The model is validated by comparing with a similar UAV data in terms of open loop dynamic stability characteristics. Using two main approaches / namely, classical and optimal, linear controllers are designed. For the classical approach, Simulink Response Optimization (SRO) tool of MATLAB&reg / /Simulink&reg / is utilized, whereas for the optimal controller approach, linear quadratic (LQ) controller design method is implemented, again by the help of the tools put forth by MATLAB&reg / . The controllers are designed for control of roll, heading, coordinated turn, flight path, pitch, altitude, and airspeed, i.e., for the achievement of all low-level control functions. These linear controllers are integrated into the nonlinear model, by carrying out gain scheduling with respect to airspeed and altitude, controller input linearization regarding the perturbed states and control inputs, and anti integral wind-up scheme regarding the possible wind-up of the integrators in the controller structures. The responses of the nonlinear model controlled with the two controllers are compared based on the military flight control requirements. The advantages and disadvantages of these two frequently used controllers in industry are investigated and discussed. These results are to be evaluated by the designers themselves based on the design criteria of a project that is worked on.