Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis proposes a design of a power supply for high-pressure discharge lamps based on a high efficiency and high power factor electronic ballast, without exciting the intrinsic acoustic resonance. The ballast consists on a bipolar buck chopper operating in continuous conduction mode (CCM), with an input filter, and an igniter circuit. It works with a switching frequency of 33 kHz and supplies the lamp in the mains frequency. The igniter circuit provides the necessary high voltage for the lamp's startup initial procedure. It is controlled by an 8 bits microcontroller, thus contributing to reduction in the number of parts and the ballast final cost, without compromising its reliability. Two possible solutions for an igniter circuit are proposed, the first based on a igniter device, and the second on a LC resonant circuit. A study on the ignition process and the required circuits to guarantee it, and a brief review on the electrical characteristics of electromagnetic ballasts are also included as secondary contributions. Experimental results with a 70W HPS lamp supplied by a 220V±20% and 60 Hz mains, are presented to validate the proposed ballast. The behavior of the experimental ballast shows that it is a good choice in avoiding unstable effects provoked by acoustic resonance phenomenon. / Esta dissertação apresenta o projeto de uma fonte de alimentação para lâmpadas de descarga em alta pressão baseada em um reator eletrônico com alto rendimento e ótimo fator de potência que não excita de forma destrutiva a ressonância acústica (AR). O reator consiste de um conversor buck bipolar operando em modo continuo (CCM), com filtro de entrada acoplado e com um circuito de ignição. O conversor opera em 33 kHz e alimenta a lâmpada em freqüência de rede. O circuito de ignição fornece a alta tensão para a formação inicial do arco elétrico. O controle do reator é implementado em um microcontrolador de 8 bits, o que contribui com a redução do número de componentes e do custo final do sistema, sem prejudicar a confiabilidade do mesmo. Duas propostas de circuito de ignição são apresentadas, uma baseada em um dispositivo ignitor, e a segunda em um circuito LC ressonante. Uma breve revisão e avaliação das características elétricas do reator eletromagnético é também apresentada a título de comparação. Um estudo do processo de ignição e os circuitos necessários a formação do arco é também incluído. Resultados experimentais para uma lâmpada HPS de 70W alimentada a partir de uma rede de 220V±20% e 60Hz são apresentados para validar o reator proposto e demonstram que este é uma boa escolha para evitar os efeitos danosos do fenômeno da ressonância acústica.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis proposes to improve the efficiency of public illumination systems by means of AC chopper based power converters. A comparative study of high performance AC/AC converters feeding high pressure sodium lamps on mains frequency is presented. These converters are obtained using standard DC/DC topologies with bi-directional switches (four quadrants). A high pressure lamp ballast design methodology is also presented, based on the suppositions of high input power factor and without exciting acoustic resonances at destructive levels. The topologies used are the Buck-Boost, Ćuk, SEPIC and ZETA operating on continuous current mode, with or without input filter, and an ignition circuit. The converters' switching frequencies are 33 kHz feeding the lamp at low frequency (mains frequency). The ignition circuit providing the high voltage required to guarantee the initial arc to start-up the lamp, is presented, analyzed and optimized in the thesis. To control the ballast a 32 bits microcontroller is used, contributing to reduce the component count and the overall system cost. The base to propose a new control design methodology and power circuit parts specification is the Brazilian standards and a comparison with the electromagnetic ballasts output waveforms. Experimental results supplying a 70 W HPS lamp, connected to the mains (220 V ±20% e 60 Hz) through the proposed ballasts, are presented in order to validate the thesis. / Este trabalho visa aprimorar os sistemas de iluminação pública aplicando reatores eletrônicos baseados em conversores CA/CA. Apresenta-se um comparativo entre conversores tradicionais CC/CC, aplicando a eles interruptores bidirecionais em tensão e corrente, de modo a alimentar a lâmpada de alta pressão de sódio na frequência da rede de alimentação, formando um conversor estático CA/CA com alto rendimento. Apresenta uma metodologia de projeto para fonte de alimentação de lâmpadas de descarga em alta pressão baseada em reatores eletrônicos com alto rendimento e elevado fator de potência, que não excitam de forma destrutiva a ressonância acústica (AR). O reator consiste dos conversores Buck-Boost, Ćuk, SEPIC e ZETA bipolares operando por modulação de largura de pulso (PWM) em modo de condução de corrente contínua (CCM), com ou sem filtro de entrada acoplado e com um circuito de ignição. O conversor opera em 33 kHz e alimenta a lâmpada na frequência da rede. O circuito de ignição fornece a alta tensão para a formação inicial do arco elétrico e neste trabalho de doutoramento foi equacionado e otimizado quando comparado ao modelo tradicional. O controle do reator é implementado em um microcontrolador de 32 bits, o que contribui com a redução do número de componentes e do custo final do sistema, sem prejudicar a confiabilidade do mesmo. As formas de onda de saída de reatores eletromagnéticos e as normas vigentes servem de base para o dimensionamento dos componentes e a obtenção de uma nova metodologia de controle. Resultados experimentais para uma lâmpada HPS de 70 W alimentada a partir de uma rede de 220 V ±20% e 60 Hz são apresentados para validar os reatores propostos.

This thesis discusses of the intake tract four-stroke ignition internal combustion engine and the filling efficiency and opportunities to increase this efficiency and consequently to optimize the course of torque and power at the specified serial engine. 3D model is the last point of this thesis.

Using alternating current in order to heat batteries at sub-zero temperatures is a method,which is investigated in-depth by an increasing number of study groups. The thesis considersthe resonance phenomenon with the intention to use alternating current amplificationand battery’s impedance in order to induce power dissipation inside the battery, and in thisway increase its temperature. A battery cell is thereby modelled as an impedance transferfunction, estimated from electrochemical impedance spectroscopy measurements, whichare taken for a LiNi 13Mn13Co13O2 cell. Note that at 1 kHz and room temperature (20 ◦C),the ohmic resistance of the selected cell amounts to only 0.76m. Five resonant circuitsare investigated and one of them is selected for further investigation, and as a basis for afilter design. The chosen resonant circuit lead to an LCL filter with current magnification.The experimental setup used for conducting practical experiments, offers the possibilityof operating the voltage source converter both as a Full-bridge and as a Half-bridge, withand without current control. For each possible configuration, an LCL filter and a currentcontroller are designed, taking into account the corresponding limitations in frequency,current and controller voltage. The filter design is based on a multiobjective optimizationmethod used to determine filter components that yield the highest gain value for everyconfiguration. The method minimizes two objective functions in order to find an optimalsolution. The first objective is the reversed absolute value of the gain, whereas thesecond one is the absolute impedance of the circuit, consisting of the filter and batterycells. The gain is thereby defined as the ratio between the induced cell current and thecurrent entering the circuit. The obtained results of the proposed method are experimentallyvalidated. Depending on how the filters were physically designed and taking intoaccount the corresponding voltage source converter configuration, gains of 16 were experimentallyachieved. Finally, the three investigated configurations are compared againstthe reference case (Half-bridge voltage source converter with current control and a singleinductor) regarding their power efficiencies. The power measurements showed that despitehigh obtained gains, the overall filter power losses remained approximately in thesame range, compared to the power losses of the reference case. This is due to the factthat stray resistances of the designed LCL filters easily reached values of around 40m,which hindered an efficient power transfer with the chosen voltage source converter andthe used battery cells. This further indicates the importance of building filters with lowstray resistances and in this thesis, it represents a primary source of improvement. / Användandet av växelströ m fö r att värma upp batterier är en metod som fö r närvarande undersö ks av ett flertal forskargupper. Detta examensarbete fokuserar kring hur resonans kan nyttjas fö r att ö ka strö mfö rstärkningen och, pådetta sätt, ö ka effektutvecklingen i batteriet (av LiNi1/3Mn1/3Co1/3O2-typ). Battericellens impedans modelleras som en ö verfö ringsfunktion vars parametrar estimerats från tidigare genomfö rda impedansspektroskopimätningar. Vid 1 kHz och rumstemperatur är den cellens ohmska resistansen endast 0.76 mΩ. Fem mö jliga resonanta kretsar har undersö kts och en av dem valts ut fö r vidare undersö kningar. The utvalda kretsen är ett LCL-filter med vilken strö mfö rstärkning åstadkoms. Den experimentella uppställningen, i vilken praktiska test har genomfö rts, medger mö jligheten att nyttja den tillhö rande omriktaren både som en helbrygga och en halvbrygga, med och utan strö mreglering. Fö r varje mö jlig omriktarkonfiguration har ett LCL-filter och en strö mreglering tagits fram, med hänsyn tagen till uppställningens begränsningar i termer av frekvens, strö moch dc-spänningsnivå. Filtren är framtagna med hjälp av en multiobjektiv optimering vilken åstadkommer hö gsta strö mfö rstärkning mö jlig fö r varje omriktare och strö mregleringsval. Metoden minimerar tvåfunktioner fö r att finna en optimal lö sning. Den fö rsta funktionen beskriver inversen påströ mfö rstärkningen och den andra lastens (bestående av filter och tillhö rande battericell) impedans absolutbelopp. Den resulterande ö har validerats experimentellt och en strö mfö rstärkningsnivåpå 16 uppnåddes. Slutligen har de olika konfigurationerna jämfö rts i termer av verknings-grad. De genomfö rda effektmätningarna visar att trots att hö ga strö mfö rstärkningsnivåer var mö jliga såresulterade de associerade filterfö rlusterna till liknande verkningsgrader fö r alla studerade konfigurationer. Resultaten understryker fö rdelarna med hö geffektiva filtervilka representerar en mö jlig väg fö r vidare undersö kningar.

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Le phénomène de résonance sol (PRS) est une instabilité pouvant survenir lorsque l’hélicoptère est au sol et le rotor est en marche ; elle peut vite aboutir à la destruction de l’appareil. L’origine de l’instabilité est un couplage entre les mouvements de roulis du fuselage posée sur le train d’atterrissage et le mouvement asymétrique de l’ensemble des pales dans le plan du rotor principal. Etudier théoriquement des alternatives de stabilisation par des absorbeurs de vibration linéaires (tuned mass dampers - TMD) et non linéaires (nonlinear energy sinks - NES) c’est le sujet de ce travail de thèse. Ces possibilités sont étudiées en ajoutant à un modèle minimal d’un hélicoptère à quatre pales identiques (rotor isotrope),précédemment étudié par l’équipe de l’ISAE, d’abord, un TMD au fuselage, puis des TMD identiques auniveau de l’articulation des pales du rotor. Ensuite, des dispositifs à raideur purement non linéaire (NES)sont considérées, d’abord, au fuselage, puis, aux pales du rotor (NES identiques). / Helicopter ground resonance (HGR) is an instability phenomenon that can occur when helicopters exhibit a spinning rotor when grounded; it can lead the structure to rapidly break apart. The phenomenon originates from a coupling between asymmetric modes of in plane blade oscillations (lead/ lag) and the roll of a grounded fuselage. The verification of alternative stabilization devices such as tuned mass dampers (TMD) and nonlinear absorbers (nonlinear energy sinks - NES) is the objective of this thesis. These possibilities are theoretically investigated by embedding a four-bladed helicopter minimal model - proposed and previously studied by the ISAE team - first, with a TMD in the fuselage, then with four identical TMDs in each blade lag hinge. Then, a NES attached to the fuselage is considered and eventually a set of four identical NES attached to the blade lag hinges of the model is proposed and analyzed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents a family of integrated electronic ballasts applied to the public lighting system. The electronic ballasts are designed to supply High-Pressure Sodium lamps according to the desired lamp operation characteristics. The viability of use High-Pressure Sodium lamps in the public lighting system of Santa Maria city is studied along this work. Another topic addressed, is the acoustic resonance phenomenon occurrence. It is explained based on a large number of works previously presented in the literature, in order to choose for a reliable method to supply the lamp. The incremental impedance of the High-Pressure Sodium lamp is defined in the frequency domain. This model is used to analyze the lamp and ballast interaction. The presented integrated electronic ballasts to supply High-Pressure sodium lamps take the advantage of low cost and simplicity providing a stable lamp operation. / Este trabalho apresenta uma proposta de integração de conversores estáticos para alimentação de lâmpadas de vapor de sódio de alta pressão (HPS), baseando-se, fundamentalmente, na viabilidade de aplicação deste tipo de lâmpadas a sistemas de iluminação pública. Ao longo do trabalho, é discutida a viabilidade de aplicação das lâmpadas HPS ao sistema de iluminação pública existente na cidade de Santa Maria- RS, evidenciando os parâmetros técnicos necessários ao projeto e desenvolvimento de reatores eletrônicos. A abordagem do fenômeno da ressonância acústica é feita de forma consistente, avaliando-se trabalhos previamente publicados, a fim de se chegar a um método confiável para se alimentar a lâmpada HPS sem a excitação deste fenômeno. Além disso, uma análise do modelo de pequenos sinais da lâmpada traz uma visão dos principais estágios a serem empregados no reator para garantir um funcionamento estável do sistema. A metodologia de integração proposta para alimentação de lâmpadas HPS, através de reatores eletrônicos, sem a excitação do fenômeno da ressonância acústica, busca a redução de custos e a simplicidade do sistema, sem deixar de considerar os procedimentos necessários a uma operação estável e confiável.

Dans cette thèse, le comportement d'un modèle mathématique permettant de transcrire la dynamique neuronale est étudié : le système de FitzHugh-Nagumo. En particulier, nous nous intéressons au caractère aléatoire d'ouverture et de fermeture des canaux ioniques d'un neurone qui reçoit ou non un stimulus. Ce caractère aléatoire de la dynamique neuronale est considéré, dans notre modèle, comme un bruit. Dans un premier temps, le comportement du modèle de FitzHugh-Nagumo a été caractérisé au voisinage de la bifurcation d'Andronov-Hopf qui traduit la transition entre l'état d'activation et l'état de repos du neurone. Classiquement, un neurone positionné à l'état de repos ne produit aucun potentiel d'action. Cependant, il a été montré un phénomène pour lequel une quantité appropriée de bruit permet la production de potentiels d'action des plus réguliers : la résonance cohérente. Le deuxième effet observé lors de simulations numériques permet au neurone d'améliorer la détection et l'encodage d'un signal subliminal : il s'agit de la résonance stochastique. De plus, cette thèse s'inscrit dans un contexte électronique puisqu'en plus de simuler numériquement le système de FitzHugh-Nagumo, les résultats de simulations ont également été confirmés en réalisant un circuit électronique. En effet, nous avons reproduit la dynamique non linéaire du système de FitzHugh-Nagumo à l'aide de ce circuit électronique. Cela a permis de mettre en évidence expérimentalement les deux phénomènes de résonance cohérente et de résonance stochastique pour lesquelles le bruit peut avoir une influence constructive sur le comportement de notre circuit électronique. / We study the nonlinear FitzHugh-Nagumo model witch describes the dynamics of excitable neural element. It is well known that this system exhibits three different possible responses. Indeed, the system can be mono-stable, oscillatory or bistable. In the oscillatory regime, the system periodically responds by generating action potential. By contrast, in the mono-stable state the system response remains constant after a transient. Under certain conditions, the system can undergo a bifurcation between the stable and the oscillatory regime via the so called Andronov-Hopf bifurcation. In this Phd thesis, we consider the FitzHugh-Nagumo model in the stable state, that is set near the Andronov-Hopf bifurcation. Moreover, we take into account the contribution of noise witch can induces two phenomena coherence resonance and stochastic resonance. First, without external driving, we show the effect of coherence resonance since a critical noise level enhances the regularity of the system response. Another numerical investigation reports how noise can allow to detect a subthreshold deterministic signal applied to the system. In this case, an appropriate amount of noise maximizes the signal to noise ratio reveling the stochastic resonance signature. Besides this numerical studies, we have also built a non linear circuit simulating the FitzHugh-Nagumo model under the presence of noise. This circuit has allowed to confirm experimentally the numerical observation of stochastic resonance and coherence resonance. Therefor, this electronic circuit contributes a framework for further experimental investigation in the field of neural sciences to better understand the role of noise in neural encoding.