This thesis presents a new modular structure of the axial flux Switched Reluctance Motor (SRM). The design consists of four stator disks with each adjacent disk rotated 30 degrees apart and four rotor disks connected to a common shaft. The proposed design aims to reduce the unwanted radial force, mitigate the torque ripple, and improve the efficiency. The modular structure distributes the radial force and torque strokes along the axial length of the motor, potentially damping the torque pulsation. In addition, the modular structure would deliver the rating power at a lower current level, reducing the overall ohmic loss. Moreover, if a fault occurs on a motor disk or its control unit, the motor would still operate through other disks, increasing the reliability of the system. To verify the effectiveness of the proposed design, the magneto-static and transient performance of the motor are compared with the conventional single layer structure using 3-D Finite-Element (FE) software tool to see that the proposed motor performs better with lower torque ripple and lower radial force than a conventional single layer structure.

Cette thèse porte sur l’optimisation du contrôle des Machines Synchrones à Réluctance Variable (MSRV) et en particulier sur la compensation des phénomènes vibratoires. Elle comprend trois points forts : le développement d’une méthode de minimisation des pulsations de couple et sa validation expérimentale, l’études des facteurs qui peuvent influencer la méthode et l’influence de cette méthode sur les autres performances de la MSRV.Tout d’abord, une méthode de contrôle permettant de compenser les ondulations de couple d’une MSRV existante a été développée. Premièrement, une équation analytique du couple est proposée et analysée afin d’exprimer la relation analytique harmonique entre le couple et les courants d’alimentation. La notion de « fonction de couple » est ensuite introduite. Une stratégie basée sur l’utilisation de cette fonction pour minimiser les ondulations du couple est présentée. Deux méthodes de réduction des ondulations de couple utilisant les différents harmoniques de la fonction de couple sont mises en évidence en. Elles ont été analysées et comparées pour répondre aux différents objectifs. Par la suite, la méthode a été validée par les résultats des simulations pour trois technologies de rotor de MSRV parmi les plus répandues. La méthode est aussi validée par la modélisation analytique et la simulation dynamique à l’aide du logiciel Matlab/Simulink ainsi que par les résultats d’expérimentation avec l’aide du banc d’essai.Ensuite, les facteurs qui peuvent influencer la méthode proposée pour réduire les ondulations de couple et les performances dynamiques ont analysés. Dans un premier temps, une amélioration sensible de l’aptitude au démarrage de la MSRV lorsque la compensation des ondulations de couple est mise en œuvre est mise en évidence. D’autre part la sensibilité de la méthode aux erreurs de mesure de position est évaluée afin de quantifier sa fiabilité dans le cas de l’utilisation d’estimateurs lors du contrôle sans capteur. Enfin, l’influence de la saturation sur la méthode proposée est aussi étudiée à l’aide d’une analyse par éléments finis du comportement magnétique de la MSRV.Finalement, l’influence de la méthode de compensation des ondulations de couple sur d’autres performances de la MSRV est analysée. Les courants optimaux ont plus harmoniques que les courants originaux. Par conséquent, les pertes dans le cuivre, dans le fer et dans les semi-conducteurs de l’onduleur sont modélisées analytiquement, calculées et comparées. Les conclusions montrent que les pertes dans le cuivre sont les plus sensibles à la compensation des harmoniques de couple tandis que les pertes dans le fer et dans l’onduleur sont faiblement affectées. D’autre part, la réduction des ondulations de couple peut changer le comportement vibro-acoustique de la MSRV. La dernière partie est consacrée à l’étude de la relation entre les ondulations de couple et le bruit. Une équation est proposée pour évaluer la variation du bruit produit par la compensation des ondulations de couple. Dans cette partie, les simulations dans Flux 2D sont effectuées pour calculer la variation du bruit. En outre, le logiciel professionnel Manatee réalisant l’analyse des vibrations et de l’acoustique est utilisé dans le but de conforter les résultats obtenus par la modélisation analytique. / This thesis aims to study the control and optimization of a synchronous reluctance machine for the purpose of improving the vibrational performance. The main works of the thesis can be classified into three parts: the proposed torque ripple reduction method, the factors which can influence the proposed method and the influence of the proposed method.At first, the torque ripple of synchronous reluctance machine is reduced by a control method. Firstly, a torque equation is proposed in order to present the relationship between torque ripple and the optimal currents. Then a new parameter, torque function, is put forward. Based on the torque function, the torque ripple reduction strategy is presented. Two different torque ripple minimizations are proposed by applying different torque function harmonics. They are analyzed and compared in order to define the optimal method. In order to test the proposed method further, the selected torque ripple minimization approach is applied to three SynRMs. The results of finite element simulations imply that the proposed method is effective to decrease the torque ripples of these three SynRMs. The proposed torque ripple reduction method is verified according to the models built in MATLAB/Simulink and the experiment results respectively.Then the factors which could influence the proposed torque ripple reduction method are analyzed. Firstly, torque function is a function of rotor position, current angle and saturation. Based on the model in Simulink, the influence of different starting position on the performance of the studied SynSR is analyzed. Besides, the estimated position errors produced by senserless control could also affect the toque ripple minimization by changing torque function. At last, the influence of saturation on the proposed torque ripple reduction method is introduced because the amplitudes of the optimal currents are increased.In addition, the influence of torque ripple reduction on the other perfomances of SynRM is analyzed. The optimal currents have more harmonics than the original sinusoidal currents. So three losses (copper losses, iron losses and inverter losses) are modeled, calculated, analyzed and compared. According to the results, the copper losses are the most sensible losses. The iron losses and the inverter losses are a little increased and the increased parts can be neglected. Besides, reducing torque ripple by adding stator currents could influence the vibro-acoustic of the studied SynRM. Thus this section aims to explain the relationship between torque ripple reduction and acoustic noise. An analytical equation is proposed in order to evaluate the variation of noise produced by torque ripple reduction. Simulations in Flux 2D have been performed in order to calculate the variation of noise resulted by torque ripple reduction. At last, the software Manatee which is professional in studying the vibration and noise is applied for the purpose of comparing the results with those of the finite element analysis.

<p>Bit-parallel addition can be performed using a number of adder structures with different area and latency. However, the power consumption of different adder structures is not well studied. Further, the effect of pipelining adders to increase the throughput is not well studied. In this thesis four different adders are described, implemented in VHDL and compared after synthesis. The results give a general idea of the time-delay-power tradeoffs between the adder structures. Pipelining is shown to be a good technique for increasing the circuit speed.</p>

Bit-parallel addition can be performed using a number of adder structures with different area and latency. However, the power consumption of different adder structures is not well studied. Further, the effect of pipelining adders to increase the throughput is not well studied. In this thesis four different adders are described, implemented in VHDL and compared after synthesis. The results give a general idea of the time-delay-power tradeoffs between the adder structures. Pipelining is shown to be a good technique for increasing the circuit speed.

Despite its simple construction, robustness and low manufacturing cost, the application areas of SR motors are remained limited due to the high level of acoustic noise and torque ripple. In this thesis work, two different type of controllers are designed and implemented in order to minimize the acoustic noise and torque ripple which are considered as the major problems of SR motors. In this scope, first the possible acoustic noise sources are investigated. A sliding mode controller is designed and implemented to reduce the shaft torque ripple which is considered as a major source of acoustic noise. The performance of the controller is experimentally tested and it is observed that especially in low speed region reduction of torque ripple is significant. The torque ripple minimization performance of the controller is also tested at different speeds and the acoustic noise levels are recorded simultaneously. Comparing the noise mitigation with the noise reduction the correlation between the acoustic noise and shaft torque ripple is investigated. The results obtained from this investigation indicated that the torque ripple is not a major source of acoustic noise in SR motors. After this finding, radial force which is the other possible acoustic noise source of SRM is taken into consideration. The effects of control parameters on radial force and the motor efficiency are investigated via simulations. With the intuition obtained from this analysis, a switching angle neuro-controller is designed to minimize the peak level of radial forces. The performance of the mentioned controller is verified through noise records under steady state conditions. Regarding to the radial force simulations and the acoustic noise measurements, it is deduced that the radial force is the major source of acoustic noise. On the other hand, another controller is designed and implemented which increases the average torque per ampere value in order to increase the efficiency of the motor. It is seen that this controller has a good effect on increasing the efficiency but does not guarantee to operate at maximum efficiency.

The aim of this PhD thesis is to find out mechanisms of the ripple initiation and formation in the chromium thin film on the glass substrate. To learn to control the ripple formation and to apply it for fabrication of diffraction gratings. In this thesis, the experimental and theoretical results of new self-organization effect of the metal thin film on the glass substrate under irradiation with a sequence of partially overlapping laser pulses are presented. The method for formation of the regular ripples and results on investigation of diffractive properties of the self-organized gratings is presented. Different types of metals are used in experiments in order to understand the reasons of regular structure formation in chromium film. A diverse behavior of the films under laser irradiation is observed depending on the metal when burst of partially overlapping pulses was applied. Experimental data is compared with simulations based on different physical phenomena in order to develop and confirm a model of ripple formation in thin chromium film under its irradiation with pulses of a nanosecond laser. The Plateau-Rayleigh instability of the cylindrical ridge formation during laser ablation appears to be the most probable process responsible for initiation of the ripple formation. The Marangoni convection of the molten metal from hot areas to cold is the stabilizing process of steady ripple formation. / Disertacijos darbo tikslas yra suprasti pagrindinius fizikinius mechanizmus, lemiančius raibulių susidarymą. Išmokti kontroliuoti raibulių formavimąsi. Panaudoti raibulių formavimąsi difrakcinių gardeliu gamybai. Rasti sąlygas, kada raibulių formavimosi galima išvengti, siekiant sumažinti kodinės stiklinės liniuotės periodą. Ištirti galimą raibulių formavimąsi skirtingų metalų dangose. Šioje daktaro disertacijoje pristatomi eksperimentiniai ir teoriniai rezultatai naujo savi-organizacijos reiškinio metalo dangos ant stiklo padėklo nanosekundinio lazerio į juostą sufokusuoto pluošto spinduliuotės poveikyje. Pristatomas naujas difrakcinių gardelių formavimo metodas panaudojant metalo savitvarką. Siekiant suprasti kas inicijuoja raibulių formavimąsi ir ar jis įmanomas visiems metalams, dangos apdribimas persiklojančiais lazerio impulsais aštriai į juostą sufokusuotu lazerio pluoštu išbandytas skirtingiems metalams. Skirtingas dangos elgesys stebimas kiekvienam metalui. Nagrinėjami pagrindiniai fizikiniai mechanizmai sukeliantys griežtai periodinių raibulių formavimąsi. Parodoma, kad raibulių formavimosi pradžia atsiranda dėl Plato-Reilio nestabilumo cilindrinės užvartos susidarymo metu. Taip pat parodoma, kad Marangoni konvekcija skystame metale yra pagrindinė jėga, lemianti nusistovėjusį periodinių raibulių formavimąsi.

Disertacijos darbo tikslas yra suprasti pagrindinius fizikinius mechanizmus, lemiančius raibulių susidarymą. Išmokti kontroliuoti raibulių formavimąsi. Panaudoti raibulių formavimąsi difrakcinių gardeliu gamybai. Rasti sąlygas, kada raibulių formavimosi galima išvengti, siekiant sumažinti kodinės stiklinės liniuotės periodą. Ištirti galimą raibulių formavimąsi skirtingų metalų dangose. Šioje daktaro disertacijoje pristatomi eksperimentiniai ir teoriniai rezultatai naujo savi-organizacijos reiškinio metalo dangos ant stiklo padėklo nanosekundinio lazerio į juostą sufokusuoto pluošto spinduliuotės poveikyje. Pristatomas naujas difrakcinių gardelių formavimo metodas panaudojant metalo savitvarką. Siekiant suprasti kas inicijuoja raibulių formavimąsi ir ar jis įmanomas visiems metalams, dangos apdribimas persiklojančiais lazerio impulsais aštriai į juostą sufokusuotu lazerio pluoštu išbandytas skirtingiems metalams. Skirtingas dangos elgesys stebimas kiekvienam metalui. Nagrinėjami pagrindiniai fizikiniai mechanizmai sukeliantys griežtai periodinių raibulių formavimąsi. Parodoma, kad raibulių formavimosi pradžia atsiranda dėl Plato-Reilio nestabilumo cilindrinės užvartos susidarymo metu. Taip pat parodoma, kad Marangoni konvekcija skystame metale yra pagrindinė jėga, lemianti nusistovėjusį periodinių raibulių formavimąsi. / The aim of this PhD thesis is to find out mechanisms of the ripple initiation and formation in the chromium thin film on the glass substrate. To learn to control the ripple formation and to apply it for fabrication of diffraction gratings. In this thesis, the experimental and theoretical results of new self-organization effect of the metal thin film on the glass substrate under irradiation with a sequence of partially overlapping laser pulses are presented. The method for formation of the regular ripples and results on investigation of diffractive properties of the self-organized gratings is presented. Different types of metals are used in experiments in order to understand the reasons of regular structure formation in chromium film. A diverse behavior of the films under laser irradiation is observed depending on the metal when burst of partially overlapping pulses was applied. Experimental data is compared with simulations based on different physical phenomena in order to develop and confirm a model of ripple formation in thin chromium film under its irradiation with pulses of a nanosecond laser. The Plateau-Rayleigh instability of the cylindrical ridge formation during laser ablation appears to be the most probable process responsible for initiation of the ripple formation. The Marangoni convection of the molten metal from hot areas to cold is the stabilizing process of steady ripple formation.

Made available in DSpace on 2016-12-12T17:38:35Z (GMT). No. of bitstreams: 1 Maria Bernardete da Silva.pdf: 1124461 bytes, checksum: af908c9af2f2467bc1dc36b3d17d4585 (MD5) Previous issue date: 2006-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The torque ripple in electric motors affects the performance of devices and machines which need precision in its control. Due to the undesirable effect of the ripple torque it has had recently an effort in the direction to get minimization strategies which permit the reduction or even elimination of this kind of torque. The goal of this work is the study and comparison between two minimization strategies of the ripple torque in hybrid step motor and apply that strategies in digital control. A step motor´s description is supplied together with other kinds of torque belong to this motors. The mathematical model for the step motor is described and based on this model has got the ripple torque´s equation which will be used in the formulation of the torque ripple minimization. To each strategy is presented a detailed mathematical foundation to the reader to be clear the development to each strategy. The first strategy presents a ripple torque´s model by hybrid step motors linearization that after linearized may be used standard methods of digital control design. The second uses an adaptative linearization to improve the hybrid step motor´s performance with low cost. By the end, a comparison between two strategies is made giving to the reader the advantages and disadvantages of each strategy. / O conjugado de ondulação em motores elétricos afeta o desempenho de máquinas e dispositivos que exijam precisão no seu controle. Devido aos efeitos indesejáveis do conjugado de ondulação tem havido recentemente um esforço no sentido de se obter estratégias de minimização que tornem possíveis a redução ou até mesmo a eliminação desse tipo de conjugado. O objetivo deste trabalho é o estudo e a comparação de duas estratégias de minimização do conjugado de ondulação em motores de passo híbrido onde as duas estratégias analisadas são aplicadas em controle digital. Uma descrição dos motores de passo é fornecida juntamente com os diversos tipos de conjugado existentes nesses tipos de motores. Um modelo matemático para o motor de passo é descrito e a partir desse modelo é obtida a equação do conjugado de ondulação que será usada na formulação dos problemas de minimização do conjugado de ondulação. Para cada uma das estratégias é apresentada em detalhes a fundamentação matemática para que o leitor tenha um claro entendimento do desenvolvimento de cada uma das estratégias. A primeira estratégia apresenta um modelo de máquina que representa as ondulações de conjugados pela linearização de motores de passo híbridos que, após linearizado permite o emprego de métodos padrões de projeto de controle digital. A segunda utiliza a linearização adaptativa para melhorar a performace do motor de passo híbrido com baixo custo. Por fim, é feita uma comparação entre as duas estratégia, apresentando-se ao leitor as vantagens e desvantagens de cada uma delas.

Synchronous generators have been used in hydropower from more than a century where, traditionally, the field current is transferred to the rotor using slip rings and carbon brushes. There are some major disadvantages following the use static excitation; regular and expensive maintenance, as well as a source of carbon dust which, due to buildup, may cause short circuits. To avoid these problems associated with slip ring exciter systems, a system that use induction to transfer power to the rotor could be used instead. Systems that utilize brushless excitation today usually regulates the current by controlling the magnetization of the exciter stator, which is comparably slower than their static counterparts. In order to allow for swift regulation of the field current from a brushless exciter, required power electronics and controllers have to be present on the rotor shaft instead. The aim of this project is to start investigating if commercially available products, which are originally indented to be used in a stationary environment, could accomplish this. The results from this study shows that it is possible to use such products to control the field current. The components were found to withstand the exposure of high g-forces and vibrations, albeit only during the relatively small amount of time in which rotary testing was performed. As such there is no certainty that the components would remain functional for the considerably longer time that any commercial use would require them to.

No description available.