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1
Carrión, O. Paola, E. Edith Ibacache, R. Rafael Guillier, R. Rodrigo Cariceo, and Juan José Kwasigroch. "Club Chopper." Tesis, Universidad de Chile, 2008. http://www.repositorio.uchile.cl/handle/2250/111575.
Full textAbstract:
Tesis para optar al grado de Magíster en AdministraciónNo disponible a texto completo
Club Chopper nace de la experiencia de vivir el mundo de las motocicletas Harley Davidson y de la observación de las conductas y actividades predominantes en los fanáticos de esta actividad. Efectivamente, al conocer a fondo este particular y específico mundo, se detectó la necesidad de contar con un lugar físico único, característico, que fuera capaz de acoger al mundo de las motocicletas de alta cilindrada de Santiago, ofreciéndole un conjunto de productos y servicios de una manera tal, que de inmediato los miembros de este grupo se hicieran parte de este concepto y lo adoptaran como su lugar, propio, personal, a su medida y deseo. Lo anterior sumado a la expansión del mercado de las motocicletas, donde se ha incrementado tres veces en volumen, entre 2005 y 2006, y con un aumento relevante para 2007 en la marca Harley Davidson, genera las condiciones óptimas para el desarrollo de este proyecto. La característica predominante de este mercado es la pertenencia, ser parte del mundo Harley. Éste además, es un referente y una aspiración para la mayor parte de los poseedores de motocicletas de otras marcas, siempre en el segmento “custom”, “chopper” o “bobber”. Esto lleva a detectar la necesidad de crear un lugar donde los “Harlistas” y otros motociclistas puedan reunirse frecuentemente, a diario muchos de ellos y donde además puedan satisfacer todas sus necesidades al respecto, desde la adquisición de una motocicleta nueva o usada, hasta la obtención de servicios para sus motocicletas, vestimenta, accesorios, repuestos y encuentro con amigos. Con lo anterior, ‘Club Chopper’ es un conglomerado comercial que consta de tres áreas básicas: a) Tienda de motos, vestimenta, accesorios y repuestos de la marca Harley Davidson, más venta y consignación de motocicletas usadas. b) Taller de mantención, servicios y transformaciones de motocicletas. c) Un pub – restaurant temático. Las tres áreas configuradas en una conformación física tal que se genere un espacio cálido, específico y único donde se pueda practicar y disfrutar de este “estilo de vida”. El negocio base es la venta de motocicletas marca Harley Davidson, para lo cual, en un inicio, se importarán las unidades desde un dealer de Estados Unidos, para, posteriormente, trabajar en la obtención de un contrato con Harley Davidson para transformarnos en dealer autorizado e importar las unidades directamente desde la matriz. Asimismo, los demás productos para la venta (vestimenta, accesorios y repuestos) también seguirán este modelo de desarrollo. El taller se desarrollará sobre la base de uno de los actuales talleres no oficiales de la marca en Chile, el cual es propiedad de uno de los personajes líderes en este ambiente y quien se incorporará a Club Chopper, aportando su conocimiento técnico, experiencia, cartera de clientes y su imagen, característica altamente relevante para el éxito del proyecto. Finalmente, se creará un pub restaurant, con ambientación ad-hoc, una carta sencilla y espacios adecuados para las reuniones periódicas de diferentes grupos de motociclistas. La particularidad es la unidad, la que dará sinergia a las tres áreas, potenciará la actividad individual y generará la característica distintiva y única del proyecto. Club Chopper se ubicará en la comuna de Las Condes, en un local arrendado, el cual se deberá remodelar para albergar la configuración adecuada de las tres actividades. Hemos estimado la inversión inicial en un monto de MM$ 270, donde la mayor parte se dedica a la remodelación del local, más la importación de un stock de motocicletas y demás ítems tanto en artículos personales como repuestos y accesorios para las motos y la implementación del restaurant. Pese a las conservadoras proyecciones de ventas, el proyecto tiene la capacidad de recuperar la inversión inicial al cuarto trimestre del segundo año de operaciones. La competencia directa que enfrentará Club Chopper será la del actual distribuidor para Chile de la marca e indirectamente, los importadores de otras marcas de motos de este segmento como Yamaha, Honda y Suzuki. Estimamos que el distribuidor H-D, por lejos el líder en el segmento, como las demás marcas, no han explotado adecuadamente los conceptos subyacentes en este mercado, por lo que Club Chopper ingresará al mercado con claras ventajas competitivas y, dada la estructura de nicho, con un rápido posicionamiento como “el lugar propio de los Harlistas” y otros motociclistas, imagen que claramente será atractiva también para un público general.
2
Hadiashar, Ali. "Chopper stabilization in analog multipliers." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35604.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 57-58).
The multiplier is a fundamental analog building block. Analog multipliers are used in many systems such as filters, neural networks, automatic gain control circuits, and phase alignment systems. As with any circuit, analog multipliers are plagued by DC offsets. When considering techniques for removing this offset, the question of continuous regulation versus calibration arises. We can easily implement a calibration method, however, how often one must calibrate becomes an issue. Additionally, calibration typically forces the multiplier to suspend normal operation while the offsets are being measured. In this thesis, a technique for continuously regulating offset in multipliers is studied in isolation. Chopper stabilization, a technique long used in DC amplifiers, is applied to analog multipliers to achieve the lowest offset reported.
by Ali Hadiashar.
S.M.
3
Allen, Kirk D. "Practical implementation of the hard switched buck chopper." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA331788.
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Murad, Thamir Faraj. "Digital control of chopper-fed DC motor drive." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/10836.
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Chang, Kee Anselmo Marco Antonio. "Diseño de un amplificador chopper de señales neuronales." Bachelor's thesis, Pontificia Universidad Católica del Perú, 2016. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8877.
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En el presente trabajo de tesis se diseña un amplificador para ser utilizado como
parte de un sistema de adquisición de señales neuronales. La topología elegida para
el desarrollo fue la de cascodo plegado de una sola salida (single ended folded
cascode), ubicando los moduladores chopper de manera que no haya limitación
debido al ancho de banda.
Debido a que este trabajo está enfocado a dispositivos implantables, se requiere
de un bajo consumo de potencia, así como una pequeña área ocupada. A estos dos
requerimientos se suma el de ruido, el cual es de gran importancia al ser esta la
primera etapa del sistema.
Se utilizó el software CADENCE para realizar distintas simulaciones que
comprueban el correcto análisis realizado. Los resultados más importantes previo a
la aplicación de la técnica chopper son: el ruido referido a la entrada de 2.92Vrms,
con una potencia consumida de 36.78uW utilizando una fuente de alimentación de
3.3V, la ganancia de lazo abierto es de 102.1dB y la ganancia de lazo cerrado es de
45.88dB con un ancho de banda de 7.96kHz. El área ocupada por el circuito es de
0.0073mm2.Tesis
6
Godoy, Philip (Philip Andrew). "Nested chopper stabilization in analog multipliers and mixers." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44379.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 97-99).
We describe a general offset-cancelling architecture for analog multiplication using chopper stabilization. Chopping is used to modulate the offset away the output signal where it can be easily filtered out, providing continuous offset reduction which is insensitive to drift. Both square wave chopping and chopping with orthogonal spreading codes are tested and shown to reduce the offset down to the microvolt level. In addition, we apply the nested chopping technique to an analog multiplier which employs two levels of chopping to reduce the offset even further. We discuss the limits on the performance of the various chopping methods in detail, and present a detailed analysis of the residual offset due to charge injection spikes. An illustrative CMOS prototype of a chopper-stabilized general-purpose multiplier in a 0.18/pm process is presented which achieves a worst-case offset of 1.5/tV. This is the lowest measured offset reported in the DC analog multiplier literature by a margin of two orders of magnitude. The prototype multiplier is also tested with AC inputs as a squarer, variable gain amplifier, and direct-conversion mixer, demonstrating that chopper stabilization is effective for both DC and AC multiplication. The AC measurements show that chopping removes not only offset, but also 1/f noise and 2nd-order harmonic distortion. The specific application of chopper stabilization to RF direct-conversion mixers is also discussed in detail, showing how it can be used to improve the sensitivity of direct-conversion receivers by reducing the mixer's offset, 1/f noise, and even-order distortion. A prototype IC of a chopper-stabilized RF mixer in a 0.18pm CMOS process is presented, along with measured results.
by Philip Godoy.
S.M.
7
Menolfi, Christian Ivo. "Low noise CMOS chopper instrumentation amplifiers for thermoelectric microsensors /." Zürich, 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13583.
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Cox, Graeme J. "A yield mapping system for sugar cane chopper harvesters." University of Southern Queensland, Faculty of Engineering and Surveying, 2002. http://eprints.usq.edu.au/archive/00004617/.
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[Abstract]: Yield maps provide essential information for the spatial analysis and evaluation of crop production management at a within field level. Technology has been developed to conduct yield mapping in various crops including grain, potatoes and forage, but as yet no technology exists for yield mapping sugar cane. The chopper harvester is the most common form ofmechanical harvester for sugar cane. Therefore, the goal of this research is to develop a yield mapping system for the chopper type sugar cane harvester.After a review, it is proposed that a suitable accuracy goal for the sugar cane mass flow sensor would be ‘less than 5% cumulative measurement error, 95% of the time (2 standard deviations), measured over a 100m2 harvest area’.Existing mass flow sensors for other crops are reviewed.Based on this review four potential techniques are proposed to measure the mass flow rate of sugar cane. These were defined as the chopper power, elevator power and feed roller separation and weigh pad. These weretested simultaneously by placing various sensors on a single harvester and comparing the sensor outputs with the mass flow rate as measured by a weigh truck. In this trial, all techniques offered potential but none produced results close to the accuracy goal. A weighing technique, known as the ‘weigh pad’, offered the most potential for improvement and potential to accurately measure the mass flow rate with a single calibration under all conditions. The weigh pad technique suffered from very small load cell sensitivity to flow rate, drift in baseline readings and susceptibility to mechanical noise/acceleration dynamics.An opportunity arose to install a complete yield mapping system on a harvester within a commercial operation. This opportunity was accepted to assess the potential for applying yield maps to the agronomic management of sugar cane. Because the weigh pad sensor required further development at this stage, chopper and elevator power were used as a measure of mass flow rate. A full yield mapping system was developed. Yield mapping, directed soil sampling and variable rate gypsum application was conducted on a case study field. Economic analysis shows a clear economic benefit when compared with standardmanagement.Analysis is conducted on the weigh pad sensor examining its susceptibility to mechanical noise/acceleration dynamics. Theory is developed to mathematically model the effects of acceleration dynamics on the accuracy of weigh pad sensor. Laboratory bench testing supported the mathematical model. From the theoretical and experimental analysis a number of conclusions are drawn:· The weigh pad should be made as light as possible to minimise the error due todynamic conditions.· Electronic analogue filters should be used to reduce the noise due to externalacceleration.· The weigh pad should be as rigid as possible to maximise its natural frequency.A new weigh pad sensor was designed based on these conclusions. Field trials indicated the effects of external accelerations dynamics were significantly reduced. Baseline drift was then found as the next major factor limiting accuracy. The baseline drift was principally caused by the secondary extractor fan of the harvester inducing a negative pressure on the weighpad. A rubber curtain placed between the weigh pad and the secondary extractor fan reduced the negative force on the weigh pad due to the secondary extractor fan by 74% (from 17 N to 4.4 N). Therefore it is recommended the curtain be used to minimise the impact of the secondary extractor fan on the baseline drift of the weigh pad.A yield mapping system has been developed for the sugar cane chopper harvester incorporating the weigh pad sensor, a ground speed sensor, a DGPS receiver, a yielddisplay/monitor and data logger. Three identical systems have been constructed and installed on three harvesters for the 1998 cane harvest season. The results show sugar cane could be yield mapped using standard yield mapping principles.The level of accuracy being achieved by the yield mapping system is less than 16% error, with 95% confidence, over a measurement area of approximately 1400 m2. Although theaccuracy achieved is not to the desired research goal, yield maps were produced with satisfactory detail to make agronomic management decisions. The reliability of the sugar cane yield mapping system under field condition in a commercial operation was satisfactory. However, two techniques are proposed (“auto-zeroing” and “batch weighing” techniques) to improve the accuracy and reliability of the weigh pad readings during wet or adverseharvesting conditions.After note: At the time of writing the NCEA along with Case Austoft (CNH) were continuing to conduct research and development on the system and are intending to make theyield mapping system available as a standard item on new harvesters and a retrofit unit on existing harvesters in the near future (C. Barret, per. comm. 2001). The proposed “autozeroing” and “batch weighing” techniques are being tested.
9
Sloboda, Alex R. "AC coupled ripple reduction method for chopper-stabilized amplifiers." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119772.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (page 44).
There exists a variety of applications where precision voltage amplifiers are required to faithfully sense and properly filter signals. While methods have been developed to create such precision amplifiers, these methods typically suffer from increased output noise. In the case of chopper amplifiers, this increased output noise comes in the form of narrow bandwidth, high frequency noise referred to as ripple noise. To reduce this ripple noise many topologies and techniques have been created and put into practice. However all of these topologies and techniques come at some cost in larger circuit area, higher power consumption, or increased noise. An AC coupled ripple reduction filter for chopper-stabilized precision amplifiers has been developed to reduce the cost of filtering out ripple noise. What follows is an explanation of ripple noise, an examination of existing ripple reduction methods, the presentation of the AC coupled ripple reduction filter, and simulated evidence of improved performance with this new method over existing methods in terms of smaller area, lower power consumption, and reduced noise.
by Alex R. Sloboda.
M. Eng.
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Said, Waleed M. "Microprocessor based speed control of a chopper-fed d.c. drive." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/14140.
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The thesis is concerned with microprocessor-based control of a d.c. drive system using armature voltage control technique with a separately-excited, chopper-fed d.c. motor. The chopper circuit has a full-bridge configuration employing gate-turn-off (GTO) thyristors, and. is capable of four-quadrant operation, making the drive both reversible and regenerative. The control of motor speed is achieved by a completely digital technique, which does not require any analog-to-digital or digital-to-analog converters. A microcomputer, specially designed and built, generates the triggering signals for the GTO's by using the unipolar switching strategy, which is accomplished totally by software using look-up tables.
11
Refoufi, L. "Steady state analysis of the chopper controlled static Kramer drive." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239814.
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Fairley, Peter Douglas. "Novel solid state modulator for the infrared : the germanium chopper." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/15503/.
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Uncooled thermal imaging cameras in the 8 to 14 µm band use pyroelectric array detectors as the preferred technology. The systems advantages offered by these uncooled detectors are those of reduced cost, complexity and power consumption. The price paid for this uncooled technology is that the image must be modulated in order to generate a change in signal intensity on the detector. Currently this is achieved using a rotating chopper blade, which introduces moving parts to the system, and has the drawbacks of size and image degradation as camera motion changes the blade's rotational speed. A need has existed for considerable time for solid state broad optical bandwidth modulation in the infrared. The application requires modulation of the 8 to 14 µm band with high 'on' state transmission, although not necessarily a very low 'off' state transmission. Crucially this must be over a relatively large (1 cm2) aperture. The modulator should be insensitive to polarisation since this would halve the image intensity from a randomly polarised scene, reducing the system signal to noise ratio. Low power consumption, compactness, and the incorporation into a low f-number optical system are the systems requirements for this application. The specification is eased only by the moderate chopping frequencies (<100 Hz) characteristic of pyroelectric detector operation. Adequate modulation using a novel method has been achieved in the 8 to 14 µm region by introducing moderate levels of excess carriers to suitably prepared germanium by excitation from a diode laser source. The process utilises inter valence band transitions from the light-hole to heavy-hole band, requiring excitation power densities in the order of Watts cm-2. This has been exploited by the construction of the first solid state modulator satisfying the requirements of thermal imaging cameras in the 8 to 14 µm band. A depth of modulation of from 95.4% (AR coated) to 4.7% transmission at 10µm using a total power density of 5.6Wcm-2 from 980nm diode lasers has been achieved in the centre of a 1cm2 aperture. The 'on' state loss at this wavelength is limited by the single-layer quarter-wavelength AR coating properties, and may be eliminated through use of a multilayer coating. There is presently no solid state modulator in the required thermal image band that even approaches this performance. The possibility of using electrical pumping to generate the required holes for the induced absorption is investigated. The design of an electrical-injection area-based modulator, modulating radiation perpendicular to the junction plane is affected by the conflicting requirements of uniform absorption across the aperture and high 'on' state transmission. A design for such a device is outlined. Modulation of a beam of radiation parallel to the junction plane is demonstrated by a reconfigured p-n junction diode to illustrate the principle.
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Tomm, Fabio Luis. "Projeto de reatores eletronicos para hid baseado no conversor chopper AC." Universidade Federal de Santa Maria, 2007. http://repositorio.ufsm.br/handle/1/8437.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis 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.
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Balasingham, Karunananthan. "A single-phase fully-regenerative converter for chopper controlled DC drives /." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59821.
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High performance dc servo-drives are often supplied from four-quadrant choppers to ensure low armature current ripple and large control loop bandwidths. In order to allow for continued regenerative braking, the dc link voltage is regulated within limits and the energy produced during braking is dissipated in resistances.In the proposed scheme the energy produced during regeneration is re-injected into the ac mains supply. The scheme consists of adding to each diode of the front end rectifier a transistor capable of conducting the reverse current, and suppressing the dc link capacitor.
The performance of the complete converter with a single phase ac mains is analysed in terms of operation in both motoring and braking modes. The advantages of the scheme are presented and its characteristics are compared to the standard chopper configuration and to the conventional phase-controlled converter systems. It is shown that the system exhibits high power factor and efficiency and is very compact.
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Jordy, Keith (Keith M. ). "Low-power amplifier chopper stabilization for a digital-to-analog converter." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46167.
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Includes bibliographical references (p. 59).Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.
Modern portable media devices demand low-power and low-noise performance from the internal digital-to-analog converter. CMOS design has allowed for oversampling sigma-delta modulation to achieve these goals. However, noise is typically limited by the kT/C noise in the switched capacitor filter following the digital modulation. These filters also require a large amount of on-chip capacitance. The goal of this project is to design a continuous-time output stage for a DAC. A continuous-time output requires much less capacitance than the SC filter. Chopper stabilization is applied to the amplifier to reduce the low-frequency noise. The challenge of this architecture is maintaining amplifier harmonic performance and transient performance. In simulations, chopper stabilization improved signal-to-noise ratio by 11dB while maintaining system level harmonic distortion performance.
by Keith Jordy.
M.Eng.
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Bryant, Angus Toby. "Simulation and optimisation of diode and IGBT interaction in a chopper cell." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597041.
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The insulated gate bipolar transistor (IGBT) is arguably the most important device currently used in power conversion at medium to high levels. This thesis presents a detailed analysis of IGBT and freewheel diode operation in the context of inductive switching, which accounts for the majority of power conversion processes. In particular, the consequences of the device behaviour on device and circuit interaction are examined. The behaviour of one device is shown to be tightly coupled to that of the other device and the circuit elements during switching. Performance, reliability, efficiency and cost are all affected by design considerations arising from the interaction of switching devices in power converters. Thus there is an incentive to ensure that the designs of devices and circuits are matched, allowing the requirements of the system as a whole to be satisfied. To achieve this, a formal numerical optimisation technique is used in conjunction with compact device models to offer a novel alternative to design iteration using finite-element simulators. Despite their perceived accuracy, these suffer from severe computational requirements and therefore offer limited ability to explore large areas of device design. The development of compact device models possessing a combination of high simulation speed and predictable accuracy was required, so that practical optimisation may take place. An example of device optimisation has shown that there is indeed insight to be gained in optimising the devices and circuit as a whole. The optimisation has the potential to investigate aspects of device operation, such as active gate drive circuits, in addition to device aspects such as device geometry. A useful example of device optimisation is given in the form of automated parameter extraction, where device parameters are optimised to match simulated results with experimental results. This allows designers to have greater confidence in device models used for converter circuit design. The future potential of optimisation is greater still, considering the advances made in handling multiple objectives and uncertainty in operating conditions. Conclusions are drawn concerning the development of IGBTs, diodes and circuits.
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PIPINO, ALESSANDRA. "Design of Analog Circuits in 28nm CMOS Technology for Physics Applications." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/158126.
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Il trend esponenziale delle tecnologie CMOS previsto dalla legge di Moore è stato ampiamento dimostrato nel corso degli ultimi tre decenni. Si è osservato uno scaling costante, caratterizzato da dispositivi sempre più piccoli, per soddisfare le esigenze delle applicazioni digitali in termini di velocità, complessità, densità circuitale e basso consumo di potenza. Ogni nodo tecnologico è rappresentato dalla minima lunghezza ottenibile, che corrisponde alla lunghezza del canale del più piccolo transistor che si può integrare.
Con l'arrivo delle tecnologie al di sotto dei 100nm, le performance dei circuiti digitali sono ulteriormente aumentate, a scapito dei progettisti analogici che si ritrovano ad affrontare nuove problematiche. Infatti, da una parte lo scaling tecnologico comporta dei vantaggi per i circuiti digitali: aumento della velocità, basso consumo di potenza, alto livello di integrazione. I circuiti analogici invece risentono negativamente dello scaling, a causa di un peggioramento del comportamento del transistor, soprattutto per le tecnologie ultra-scalate. In queste ultime infatti, effetti del secondo ordine, fino a prima del tutto trascurabili, diventano importanti e iniziano ad essere dominanti, influenzando il funzionamento e le performance dei dispositivi. Per esempio, basso guadagno intrinseco del MOS, swing ridotto, problemi di punto operativo e elevata variabilità dei parametri, sono solo alcune delle difficoltà derivanti dallo scaling. I progettisti analogici devono far fronte a questi problemi in diverse fasi della progettazione, sia circuitale che di layout. Nonostante ciò, la progettazione di circuiti analogici in tecnologie così scalate in molti casi è determinante. Per esempio, in molti sistemi mixed-signal, dove coesistono circuiti analogici e digitali e sono necessarie alte performance ad alta frequenza, l’uso di queste tecnologie anche per la parte analgica diventa una scelta obbligata. Oppure ci sono gli esperimenti di fisica ad alta energia, dove la scelta di tecnologie scalate è strategica. Infatti in queste applicazioni, i circuiti elettronici sono esposti ad alti livelli di radiazione con conseguente peggioramento delle performance e fenomeni di malfunzionamento. Dato che il danno da radiazione è proporzionale allo spessore dell'ossido, è evidente che per i dispositivi più piccoli, il danneggiamento è inferiore. In questa tesi, i trend e le principali problematiche derivanti dall'uso di tecnologie molto scalate sono analizzati nel primo capitolo, seguiti poi dalla presentazione di circuiti integrati in tecnologia CMOS 28nm. Il primo circuito presentato nel secondo capitolo è un Fast-Tracker front-end (FTfe) per la rilevazione di cariche. In particolare il sistema di read-out è stato implementato a partire dalle principali specifiche e soluzioni circuitali già usate per la rilevazione di muoni nell'esperimento ATLAS. Il front-end proposto è in grado di rilevare un evento e subito dopo resettare il sistema in maniera tale da rendere il FTfe già pronto per il prossimo evento, evitando lunghi tempi morti. Il secondo circuito, presentato nel terzo capitolo ed anch'esso integrato in tecnologia CMOS 28nm, è un amplificatore per strumentazione di tipo Chopper. Gli amplificatori per strumentazione sono elementi chiave nelle applicazioni per sensori, dove vengono usati per amplificare segnali tipicamente piccoli (dell'ordine dei mV) e a bassa frequenza. Per questo motivo risulta importante ridurre o addirittura eliminare l'offset e il rumore flicker in ingresso, segnali che si sovrappongono al segnale utile da rilevare ed introdotto dallo stesso circuito elettronico. L'amplificatore per strumentazione proposto usa una tecnica di modulazione, chiamata chopper, per ridurre i contributi di rumore flicker ed offset. Inoltre l'intero amplificatore è stato progettato per lavorare in regione di sottosoglia, dati i problemi dovuti alla tecnologia fortemente scalata.The exponential trend of the complementary metal-oxide-semiconductor (CMOS) technologies predicted by Moores law has been successfully demonstrated over the last three decades. A constant downscaling of CMOS technologies with smaller and smaller device size has been developed, in order to comply with requirements on speed, complexity, circuit density and power consumption of advanced high performance digital applications. The minimum reachable length, which corresponds to the half the length of the channel of the smallest transistor that can be manufactured, represents every following technological node. With the arrival of nanoscale (sub-100nm) CMOS technologies, digital performance improve further, but many new challenges have been introduced for analog designers. In fact, for the digital circuits CMOS scaling-down leads to several benefits: speed improvement, reduced power consumption, high integration and complexity level. The analog circuits, instead, strongly suffers from the ScalTech trend, because the MOS behavior dramatically changes through the different technological nodes and especially for the ultra-scaled ones, where second order effects, previously negligible, become very important and start to be dominant, affecting its performance. For instance, lower intrinsic DC-gain, reduced dynamic range, operating point issues and larger parameter variability are some of the problems due to scaling-down. Analog designers must face this problems at different phases of the design, circuital and layout. Despite that, the design of analog circuit in sub-nm technologies is mandatory in some cases or can be even helpful in others. For example, in mainly mixed-signal systems, the read-out electronic requires high frequency performance, so the choice of deep submicron technology is mandatory, also for the analog part. Other types of applications where using scaled technology is even strategical are the high-energy physics experiments, where read-out circuits are exposed to very high radiation levels with consequent performance degradation and breakdown events. Since radiation damage is proportional to gate oxide volume, smaller devices exhibit lower radiation detriment. It has been demonstrated in fact, that 28nm CMOS technology devices are capable to sustain 1Grad-TID exposure, not possible with previous technologies. In this thesis, the main key challenges in ultra-scaled technologies are analyzed in the first chapter, and then integrated circuits designed in 28nm CMOS technology are presented. The first circuit design, presented in the second chapter and integrated in 28nm CMOS technology, is a Fast-Tracker front-end (FTfe) for charge detection. The read-out system has been developed starting from the main specifications and circuital solutions already adopted for muon detection in ATLAS experiment. The proposed front-end is able to detect an event and soon after to reset the system in order to make the FTfe already available for the following event, avoiding long dead times. The architecture is analyzed in detail, followed by the layout choices and the performance results. The second circuit design presented in the third chapter and always integrated in 28nm CMOS technology, is a Chopper instrumentation amplifier. Instrumentation amplifiers are the key building blocks in sensor and monitoring applications, where they are used to sense and amplify usually very small (sub-mV) and low frequency signals. For this reason it is important to reduce or eliminate the input offset and flicker noise, which cover and disturb the main signal to be detected. The proposed amplifier use a modulation technique, called chopper, in order to meet the low offset and low flicker noise requirements. Moreover it has been modeled to operate in sub-threshold region, in order to address the scaling problems. After the architecture description, layout and results of the integrated prototype are shown.
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Spro, Ole Christian B. "Reactive Power Compensation and Active Filtering Capabilities of the Step-down AC Chopper." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23617.
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The Step-down AC Chopper (hereby referenced as "AC Chopper") has been presented in recent academic papers as a possible solution for reactive compensation. The goal of this project was to investigate and evaluate the topology to see if the praise could be justified. In addition, this project set a goal to take the research one step further by investigating if the uses of the AC Chopper could be expanded to include active filtering. The ability of the AC Chopper converter to produce harmonic current was investigated. This was the first step in developing the AC Chopper's active filtering functionality. Theorems were developed and simulations were performed with both open and closed loop control. The results show that using the AC Chopper to produce harmonic current is very difficult if not impossible. This is due to intrinsic characteristics of the topology which leads to the converter producing multiple harmonics for a single control input frequency. Hence it was concluded that the AC Chopper is not fit for performing active filtering and that the results do not support continuing any further research on the AC Chopper's filtering capabilities.A prototype of the converter was developed and built to compare the simulations against real observed behavior. The development process has been well documented in this thesis. Open loop control of the prototype was successfully implemented. The results show a good relation between the theory and the measured values. There are certain challenges connected to the realization of the AC Chopper, and the ways of dealing with these challenges have been described herein. The topology was also compared to available technology to evaluate the competitiveness regarding reactive compensation at fundamental frequency. The AC Chopper was not found advantageous compared to the VSI, a modern available solution. The efficiency of the AC Chopper has been found to be slightly higher in simulation, but this has yet to be validated with tests on real prototypes. In addition to lacking the filtering capabilities, the AC Chopper has other disadvantages including expensive components and greater volume. Together the findings in this report suggests that the AC Chopper should be limited to use in single phase systems for reactive compensation at fundamental frequency in open loop control.
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Raimondo, Giuliano. "Power quality improvements in 25kV 50 Hz railway substation based on chopper controlled impedances." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0004/document.
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Ce travail est le résultat d'une collaboration entre le laboratoire LAPLACE, la "Seconda Università degli Studi di Napoli" (SUN) et la Société National des Chemins de fer Français SNCF. Le sujet de recherche concerne l'utilisation de dispositifs électroniques de puissance dans les sous stations ferroviaires 25kV/50Hz afin d’améliorer la qualité de l'énergie électrique. Dans le transport ferroviaire, le système d'électrification monophasé 25kV/50Hz est largement diffusé en particulier pour les lignes ferroviaires à grande vitesse. Bien qu'aujourd'hui les systèmes d’alimentation en courant continu soient encore largement utilisés, l'adoption du courant alternatif monophasé offre des avantages économiques pour les infrastructures d'environ 30% en termes d'investissement, d'exploitation et d'entretien. Initialement, compte tenu de la simplicité du circuit, il n'y avait aucune nécessité d'intégrer de l'électronique de puissance dans les sous stations. Toutefois, au cours de la décennie passée, l'intérêt pour ces équipements est apparu car ils peuvent apporter une solution d'optimisation du réseau lorsque le trafic augmente ou lorsqu’une nouvelle sous station est envisagée. Deux principaux types de dispositifs sont installés aujourd'hui sur le réseau ferré français : les compensateurs de puissance réactive et les compensateurs de déséquilibre de tension. Cette thèse présente de nouvelles topologies de compensateurs basées sur le concept d’impédances contrôlées par gradateur MLI. Comparées aux solutions existantes, ces topologies ont des caractéristiques particulièrement intéressantes en termes de pertes dans les semi-conducteurs et de volume des composants réactifs. Le manuscrit contient trois parties principales: La première partie présente le principe de l’électrification en 25kV/50Hz et souligne l’intérêt d’installer des moyens de compensation statique dans les sous stations. Après une description des solutions actuellement utilisées, le concept d’impédance contrôlée par gradateur MLI (CCI : Chopper Controlled Impedance ) est ensuite présenté. La deuxième partie du travail concerne l'utilisation du concept de CCI pour la compensation de puissance réactive. La sous-station SNCF de Revest est considérée comme cas d’étude. Celle-ci est équipée d'un transformateur monophasé de 60MVA dont le primaire est connecté à une ligne de transport 225kV. Deux topologies de compensateur de puissance réactive, basées sur des montages abaisseur ou élévateur de tension sont présentées. Le dimensionnement des gradateurs est effectué sur la base d'une campagne de mesures réalisée à la sous station. Des simulations numériques utilisant des formes d’ondes réelles de courant et de tension sont présentées. Des résultats expérimentaux effectués à la plateforme de test de la SNCF sur un prototype de 1,2MVAR permettent de valider le concept de CCI. La dernière partie du travail concerne le problème du déséquilibre de tension en amont de la sous station. Un circuit de Steinmetz « actif », toujours basée sur des gradateurs MLI, est présenté et étudié. La sous station SNCF d'Evron est alors considérée comme cas étude. Celle-ci comporte un transformateur de 32MVA et est connectée à une ligne de transmission 90kV. Les mesures effectuées sur le site permettent le dimensionnement du compensateur ainsi que l’utilisation des formes d'onde réelles de courant et de tension dans les simulations numériques. Une comparaison avec des solutions classiques basées sur des onduleurs 2 niveaux et 3 niveaux souligne les avantages de la solution proposée. Ainsi, les résultats des calculs et des simulations montrent que l'énergie stockée dans les éléments réactifs est réduite d’un facteur six et que les pertes dans les semi-conducteurs sont réduites de 40%. Des résultats expérimentaux obtenus sur une maquette de 1.5 kVA permettent de valider le principe du circuit de Steinmetz actifThis work is the result of collaboration between the LAPLACE laboratory, the “Seconda Università degli Studi di Napoli” (SUN) and the French national railways operator SNCF. The research topic treated herein concerns the use of power electronic devices in 25kV/50Hz railways substations to achieve power quality improvements. In railway transportation, single-phase 25kV-50Hz electrification system is widely diffused especially for high-speed railway applications. Although electrified DC systems are still widely applied, the adoption of AC single-phase system offers economical advantages for the infrastructures of about 30% in terms of investment, exploitation and maintenance. In early ages, due to its very simple diagram, there was no necessity to integrate power electronics in substations. However, for the last decade, the interest in power electronic equipments raised since they can provide the solution for network optimization when traffic increases or when a difficulty is foreseen for a substation implementation. Two types of devices are implemented today on the French Railway Network: Reactive Power compensators and Voltage Unbalance compensators. This thesis presents an investigation into new topologies based on the concept of “Chopper Controlled Impedances”(CCI). Compared to existing solutions, the new topologies show interesting features in terms of semi-conductor losses reduction and volume of reactive components. The manuscript is developed through three main parts: Firstly, the French railways system is introduced and the interest in installing power electronic compensators in substations is highlighted. After a brief description of currently used solutions, the CCI concept is presented: the use of Pulse Width Modulated AC Choppers allows achieving structures which behave as variable impedances. In the second part, the use of CCI structures in reactive power compensation is investigated. The SNCF substation of Revest is under study. It is equipped by a 60MVA single phase transformer with the primary side connected to a 225kV transmission line. Based on the step-down or step-up functioning mode of CCIs, two topologies of reactive power compensator are presented. The converter design is developed on the base of a measurement campaign carried out at the substation. Numerical simulations using real current and voltage waveforms are presented. Finally, experimental results carried out at the SNCF test platform on a 1.2MVAR prototype are shown. In the last part, the problem of voltage unbalance is treated. Using the concept of CCI, the feasibility of an active Steinmetz circuit based on AC choppers is explored. As a case study, the substation of Evron is considered. It is a 32MVA substation connected to a 90kV transmission line. Measurements carried out on the substation site allow the compensator design and the possibility to consider real waveforms for current and voltage in numerical simulations. A comparison with classical solution based on two levels VSI and three levels NPC-VSI highlights the advantages of the proposed solution. Calculation and simulation results show that the stored energy in reactive elements is reduced by a factor six whereas the semiconductor losses are 40% lower. Experimental results obtained on a scaled demonstrator (1.5 kVA) validate the principle of the active Steinmetz circuit
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Raimondo, Giuliano. "Power quality improvements in 25 kV 50 Hz railways substation based on chopper controlled impedances." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2012. http://tel.archives-ouvertes.fr/tel-00682719.
Full textAbstract:
Ce travail est le résultat d'une collaboration entre le laboratoire LAPLACE, la "Seconda Università degli Studi di Napoli" (SUN) et la Société National des Chemins de fer Français SNCF. Le sujet de recherche concerne l'utilisation de dispositifs électroniques de puissance dans les sous stations ferroviaires 25kV/50Hz afin d'améliorer la qualité de l'énergie électrique. Dans le transport ferroviaire, le système d'électrification monophasé 25kV/50Hz est largement diffusé en particulier pour les lignes ferroviaires à grande vitesse. Bien qu'aujourd'hui les systèmes d'alimentation en courant continu soient encore largement utilisés, l'adoption du courant alternatif monophasé offre des avantages économiques pour les infrastructures d'environ 30% en termes d'investissement, d'exploitation et d'entretien. Initialement, compte tenu de la simplicité du circuit, il n'y avait aucune nécessité d'intégrer de l'électronique de puissance dans les sous stations. Toutefois, au cours de la décennie passée, l'intérêt pour ces équipements est apparu car ils peuvent apporter une solution d'optimisation du réseau lorsque le trafic augmente ou lorsqu‟une nouvelle sous station est envisagée. Deux principaux types de dispositifs sont installés aujourd'hui sur le réseau ferré français : les compensateurs de puissance réactive et les compensateurs de déséquilibre de tension. Cette thèse présente de nouvelles topologies de compensateurs basées sur le concept d'impédances contrôlées par gradateur MLI. Comparées aux solutions existantes, ces topologies ont des caractéristiques particulièrement intéressantes en termes de pertes dans les semi-conducteurs et de volume des composants réactifs. Le manuscrit contient trois parties principales: La première partie présente le principe de l'électrification en 25kV/50Hz et souligne l'intérêt d'installer des moyens de compensation statique dans les sous stations. Après une description des solutions actuellement utilisées, le concept d'impédance contrôlée par gradateur MLI (CCI : Chopper Controlled Impedance ) est ensuite présenté. La deuxième partie du travail concerne l'utilisation du concept de CCI pour la compensation de puissance réactive. La sous-station SNCF de Revest est considérée comme cas d'étude. Celle-ci est équipée d'un transformateur monophasé de 60MVA dont le primaire est connecté à une ligne de transport 225kV. Deux topologies de compensateur de puissance réactive, basées sur des montages abaisseur ou élévateur de tension sont présentées. Le dimensionnement des gradateurs est effectué sur la base d'une campagne de mesures réalisée à la sous station. Des simulations numériques utilisant des formes d'ondes réelles de courant et de tension sont présentées. Des résultats expérimentaux effectués à la plateforme de test de la SNCF sur un prototype de 1,2MVAR permettent de valider le concept de CCI. La dernière partie du travail concerne le problème du déséquilibre de tension en amont de la sous station. Un circuit de Steinmetz " actif ", toujours basée sur des gradateurs MLI, est présenté et étudié. La sous station SNCF d'Evron est alors considérée comme cas étude. Celle-ci comporte un transformateur de 32MVA et est connectée à une ligne de transmission 90kV. Les mesures effectuées sur le site permettent le dimensionnement du compensateur ainsi que 'utilisation des formes d'onde réelles de courant et de tension dans les simulations numériques. Une comparaison avec des solutions classiques basées sur des onduleurs 2 niveaux et 3 niveaux souligne les avantages de la solution proposée. Ainsi, les résultats des calculs et des simulations montrent que l'énergie stockée dans les éléments réactifs est réduite 'un facteur six et que les pertes dans les semi-conducteurs sont réduites de 40%. Des résultats expérimentaux obtenus sur une maquette de 1.5 kVA permettent de valider le principe du circuit de Steinmetz actif.
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Turner, Clifton C. "Design and implementation of a zero-voltage-switching, pulse-width-modulated, high-frequency, resonant buck chopper." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA371024.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): Robert W. Ashton, John G. Ciezki. Includes bibliographical references (p. 137-138). Also Available online.
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Benmessaoud, Messaouda. "Recherches sur l'Acheuléen et l'Ahaggar : les matières premières lithiques ; L'outillage lithique, rapport éclats/outils ; Le cadre statigraphique et chronologique : (Exemple du site Téhéntawek-Idelès)." Thesis, Paris 1, 2014. http://www.theses.fr/2014PA010575/document.
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La thèse présentée ici actualise les anciennes données sur l’Acheuléen de l’Ahaggar, bien que ces données ne sont pas nombreuses et toutes datées du 20eme siècle. Mais pour reprendre une nouvelle ère de recherche sur le sujet, il est bien évident de les évoquer. Malgré les fructueuses découvertes dans de nombreux sites paléolithiques inférieurs, dans l’Ahaggar, aucun intérêt scientifique n’a été apporté, notamment aux nombreuses collections lithiques interposées dans plusieurs laboratoires de recherches scientifiques. Le nouveau site « Téhéntawek » Acheuléen découvert dans la région d’Idelès, au cœur du Sahara central, dans l’Ahaggar et fouillé avec des nouvelles méthodes pédagogiques instaurées dans la préhistoire actuelle, nous a livré en 2008 et 2010 un matériel lithique intéressant et très représentatif de l’industrie acheuléenne. Ces démarches sont considérées comme rénovatrices de la préhistoire saharienne. La prospection appropriée et adéquate à l’environnement, l’adaptation du travail du terrain au contexte rocheux de la région de l’Ahaggar, nous ont permis de reconsidérer le terrain saharien. L’étude technologique du matériel lithique a fourni une diversité d’outils et une coexisté de chopper, biface et hachereau, nombreux sont les éclats bruts, très compatibles avec les nucléus. Les matières premières lithiques utilisées pour le façonnage sont locales. Les résultats des analyses réalisées, sur les sédiments prélevés ont fourni de nouvelles données, notamment une ouverture sur le paléoenvironnement de l’Ahaggar. Ainsi le site Téhéntawek nous a offert des informations pertinentes sur la maitrise de l’homme dans cet environnement actuellement saharienThe thesis presented here updates the old data on the Acheulian of the Ahaggar, although these date are few in number and all dated 20th century. But it is obvious to mention them to borrow a new er of research on the subject. Despite the fruitful discoveries in many lower Palaeolithic sites in the Ahaggar, no scientific interest have been provided to many lithic collections interposed in several laboratories for scientific research. The new site “Téhéntawek” Acheulean discovered in the region of Idelès in the central Sahara of the Ahaggar and excavated with new pedagogical methods introduced in the present prehistory, has delivered in 2008 and 2010 an interesting lithic materials representative of the Acheulian industry. These approaches are considered renovative of the Saharan prehistory. The appropriate and adequate environmental of exploration, the adaptation of work to the rocky terrain of the Ahaggar region, have allowed us to reconsider the Saharan terrain. The study of lithic technology has provided a variety of tools and coexisted chopper, biface and cleaver, many raw chips, very consistent with the nucleus. Lithic raw materials used for shaping are local. The results of analyses on the sediments provided new data, including an opening on the paleoenvironment of the Ahaggar. Thus Téhéntawek site offered us with relevant information on the mastery of man in this currently Saharan environment
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Bělíček, David. "Řízení krokového motoru mikrokontrolérem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218073.
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Subject of this thesis is introduction to questions of stepping motors control. The thesis characterizes basic principles some types of stepping motor, their features and control methods. These knowledges are consequently used for proposition of controlling circuit for driving stepping motor using microcontroller.
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Superczynski, Matthew J. "Analysis of the Power Conditioning System for a Superconducting Magnetic Energy Storage Unit." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34860.
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Superconducting Magnetic Energy Storage (SMES) has branched out from its application origins of load leveling, in the early 1970s, to include power quality for utility, industrial, commercial and military applications. It has also shown promise as a power supply for pulsed loads such as electric guns and electromagnetic aircraft launchers (EMAL) as well as for vital loads when power distribution systems are temporarily down. These new applications demand more efficient and compact high performance power electronics.
A 250 kW Power Conditioning System (PCS), consisting of a voltage source converter (VSC) and bi-directional two-quadrant DC/DC converter (chopper), was developed at the Center for Power Electronics Systems (CPES) under an ONR funded program. The project was to develop advanced power electronic techniques for SMES Naval applications. This thesis focuses on system analysis and development of a demonstration test plan to illustrate the SMES systems' ability to be multitasked for implementation on naval ships. The demonstration focuses on three applications; power quality, pulsed power and vital loads.
An integrated system controller, based on an Altera programmable logic device, was developed to coordinate charge/discharge transitions. The system controller integrated the chopper and VSC controller, configured applicable loads, and dictated sequencing of events during mode transitions.
Initial tests with a SMES coil resulted in problems during mode transitions. These problems caused uncontrollable transients and caused protection to trigger and processors to shut down. Accurate models of both the Chopper and VSC were developed and an analysis of these mode transition transients was conducted. Solutions were proposed, simulated and implemented in hardware. Successful operation of the system was achieved and verified with both a low temperature superconductor here at CPES and a high temperature superconductor at The Naval Research Lab.Master of Science
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Sámelová, Vendula. "Technologické parametry elektrojiskrového řezání drátovou elektrodou." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228642.
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The work deals with the technology of electrical discharge machining using a wire electrode. Described are machines, tools, wire electrode cutting parameters and advantages of this technology. The aim of the work is to quantify the cutting area with respect to dimensional accuracy, make an analysis of surface layer state and quality after wire cutting, and describe factors affecting this layer. In particular, emphasis is put on tool steel cutting.
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Amghar, Bilal. "Modélisation, observabilité et commande de convertisseurs multicellulaires parallèles dans un environnement dédié." Phd thesis, Université de Cergy Pontoise, 2013. http://tel.archives-ouvertes.fr/tel-00880757.
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Les convertisseurs de puissance multicellulaires trouvent une place privilégiée dans le contrôle des systèmes de très forte puissance. Dans ce travail de thèse une nouvelle classe de convertisseurs de puissance est étudiée les Convertisseurs Multicellulaires Parallèles (CMP). La topologie de ces convertisseurs repose sur une association de n cellules de commutationinterconnectées par l'intermédiaire d'inductances indépendantes, appelées aussiinductances de liaison. Le CMP permet d'atteindre un courant de sortie égal à n fois le courant d'entrée du convertisseur, l'inconvénient majeur de ce type de convertisseur est le déséquilibrage des courants de branches . Dans le but de réduire et d'économiser le nombre de capteurs, nous avons proposé dans la première partie de la thèse une analyse d'observabilité spécifique à une classe de système dynamique hybride appelée Z(TN)-Observability et synthétisé un observateur hybride en utilisant l'algorithme super twisting. La deuxièmepartie du travail a été consacrée à la synthèse d'une loi de commande pour la régulation des courants de branches. En effet, le régulateur proposé est un régulateur hybride en basant sur la modélisation par réseaux de pétri de l'algorithme de contrôle. Enfin, Les deux parties théoriques sont suivies par une réalisation pratique d'un CMP à trois cellules de commutation pour valider les deux approches proposées. Les résultats expérimentaux nous ont montré les performances de l'observateur et le régulateur de courant et de tension de sortie.
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Arsoy, Aysen. "Electromagnetic Transient and Dynamic Modeling and Simulation of a StatCom-SMES Compensator in Power Systems." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27225.
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Electromagnetic transient and dynamic modeling and simulation studies are presented for a StatCom-SMES compensator in power systems. The transient study aims to better understand the transient process and interaction between a high power/high voltage SMES coil and its power electronics interface, dc-dc chopper. The chopper is used to attach the SMES coil to a StatCom. Following the transient study, the integration of a StatCom with SMES was explored to demonstrate the effectiveness of the combined compensator in damping power oscillations. The transient simulation package PSCAD/EMTDC has been used to perform the integrated modeling and simulation studies.
A state of the art review of SMES technology was conducted. Its applications in power systems were discussed chronologically. The cost effective and feasible applications of this technology were identified. Incorporation of a SMES coil into an existing StatCom controller is one of the feasible applications, which can provide improved StatCom operation, and therefore much more flexible and controllable power system operation.
The SMES coil with the following unique design characteristics of 50MW (96 MW peak), 100 MJ, 24 kV interface has been used in this study. As a consequence of the high power/ high voltage interface, special care needs to be taken with overvoltages that can stress the insulation of the coil. This requires an investigation of transient overvoltages through a detailed modeling of SMES and its power electronics interface. The electrical model for the SMES coil was developed based on geometrical dimensions of the coil. The interaction between the SMES coil and its power electronics interface (dc-dc chopper for the integration to StatCom) was modeled and simulated to identify transient overvoltages. Transient suppression schemes were developed to reduce these overvoltages. Among these are MOV implementation, surge capacitors, different configurations of the dc-dc chopper.
The integration of the SMES coil to a StatCom controller was developed, and its dynamic behavior in damping oscillations following a three-phase fault was investigated through a number of simulation case studies. The results showed that the addition of energy storage to a StatCom controller can improve the StatCom-alone operation and can possibly reduce the MVA rating requirement for the StatCom operating alone. The effective location selection of a StatCom-SMES controller in a generic power system is also discussed.Ph. D.
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Duan, Hongxu. "Generation and printing of strictly monodisperse droplets." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5931.
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Highly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: “Periodic Electro Hydro-dynamic Chopper” termed as “PEHD chopper”, and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet.
We first derived the governing equations for a circular inviscid liquid jet under transverse electric fields. The electric fields were obtained through numerical simulation. Then we used a high speed camera (up to one million frames per second) to visualize the jet break-up as well as the droplets' size and shape.
The experiments show that the PEHD chopper can effectively “chop” a neutral micro-jet and generate highly monodisperse micro-droplets, which diameter range from 100 &"181;m to 500 &"181;m. To reduce the droplet size, PEHD chopper with a butterfly design is applied on a typical single electrospray. In this configuration, the jet swings at long wavelengths (?>?R), where ?R is the Rayleigh wave length, but breaks up into highly monodisperse droplets near 2?R and ?R without satellite droplets. The butterfly configuration combined with electrified jet expands the diameter range into 20 &"181;m to 100 &"181;m.
Finally, we demonstrate the electrospray printing of Polymer Derived Ceramics (PDC) for sensor applications in harsh environment. A modified single ES with an additional driving electric field is used to directly print PDC precursor without mask, we achieved 1D feature as narrow as 35 &"181;m and a micro pentagram pattern. Moreover, after pyrolysis of PDC at 1100 °C in nitrogen, amorphous alloys of silicon, carbon and nitrogen (SiCN) are obtained. The samples exhibit excellent good integrity and adhesion to the substrate.M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Miniature Engineering Systems
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Lowinsky, Luc Anthony. "Nouvelle topologie de Compensateur de Puissance Réactive pour les Réseaux Ferrés 25 kV / 50 Hz." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0036/document.
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Le travail présenté dans ce mémoire s’est déroulé dans le cadre d’une collaboration entre le groupe Convertisseur Statique du laboratoire LAPLACE et le département " Installations Fixes de Traction Electrique " de la Direction de l’Ingénierie de la SNCF. Aujourd'hui, la majorité du trafic sur le réseau ferré monophasé 25 kV / 50 Hz est assurée par des locomotives équipées de redresseurs contrôlés à thyristors. Du fait de l'augmentation du trafic, l'utilisation de ces locomotives nécessite la mise en place de moyen de compensation de puissance réactive afin de maintenir la tension caténaire à un niveau acceptable et de réduire la facture en énergie réactive. La correction du facteur de déplacement est réalisée en partie par des batteries de compensation fixes dont lapuissance est limitée par la tension maximale admissible à vide sur la caténaire. Afin d’adapter le niveau de compensation à la consommation, la partie fixe est complétée par un dispositif réglable basé sur une réactance contrôlée par des thyristors. Bien qu’il soit simple dans son principe, ce dispositif nécessite un filtrage des harmoniques en basse fréquence avec des circuits LC volumineux. L’objectif de cette thèse est de proposer une nouvelle topologie de compensateur de puissance réactive à haut rendement et utilisant un contrôle à modulation de largeur d’impulsion dans le but de minimiser le volume des éléments de filtrage. La première partie de ce mémoire est consacrée à une étude comparative de différentes topologies du point de vue des pertes dans les semi-conducteurs et du dimensionnement des éléments de filtrage associés. Les résultats de cette étude montrent que les topologies à base de gradateurs MLI, constituent les solutions les plus intéressantes pour réaliser le compensateur. La deuxième partie du travail concerne l’étude de l’insertion d’un compensateur à base de gradateurs MLI sur le réseau ferré avec la prise en compte des interactions harmoniques. Le cas d’étude concerne une sous-station où doit être implantée une compensation variable de 3 MVAR. Un relevé des courants délivrés par la sous-station a été effectué dans le but d’analyser leur contenu harmonique. Une modélisation de la sous-station et du compensateur est ensuite proposée et des simulations temporelles de l’ensemble sont réalisées en prenant en compte les formes d’ondes réelles des courants absorbés par les trains. Finalement, cette étude par simulation permet d’affiner le dimensionnement du compensateur à gradateurs MLI et des éléments de filtrage associés. Elle met en évidence l’avantage d’une solution, avec des gradateurs MLI en montage élévateur de tension, qui fonctionne sans transformateur et réutilise les batteries de compensation fixes déjà installées en sous-station à la fois comme diviseur de tension et éléments de filtrage. Afin de valider le principe de cette nouvelle topologie de compensateur statique de puissance réactive, un démonstrateur de 1,2 MVAR est mis en oeuvre et testé sur une plateforme d'essai de la SNCFThe work presented in this thesis is the result of collaboration between the Static Converters research group of LAPLACE Laboratory and the department "Installations Fixes de Traction Electrique" of the Engineering Division of the French Railways company, SNCF. Nowadays, most of the traffic in 25 kV – 50 Hz lines is achieved by old locomotives equipped with thyristor rectifiers. As traffic and load increase, reactive power compensation devices are required to keep the overhead line voltage at acceptable level and to reduce the spending for reactive power. The basic power factor correction is completed by fixed compensation banks. But the difficulty of such configuration is the no-load operation of overhead lines. The voltage can increase out of the 29 kV standard limit and to avoid this problem, variable reactive power compensator is often added to the fixed compensation banks. Nowadays, SNCF is equipped with thyristor based static VAR compensators (SVC). The main drawback of this topology is the requirement of a large LC shunt filter tuned for the third harmonic. The goal of this thesis is to find a new high-efficiency topology of STATic COMpensator (STATCOM) using PWM control to minimize the filtering components. The first part of this thesis focuses on a comparative study of different topologies in terms of semiconductor losses and filter elements size. The results of this study show that the topologies based on PWM AC Chopper are the most interesting solutions to achieve the compensator. The second part of the work concerns the influence of the connection of a STATCOM to a substation and focuses on the harmonic interactions with locomotives. The study case concerns a high traffic substation where a 3 MVAR STATCOM should be installed. Substation output current measurement was carried out in order to analyze its harmonic content. Models of the substation and the STATCOM are then proposed and simulations using real current waveforms are performed. Finally, this simulation study helps to refine the features of the AC Chopper topology and its filter elements. It highlights the advantage of a solution, with boost AC Choppers which operate without transformer and reuse the fixed compensation banks already installed in the substation as voltage divider and filter. To validate the principle of this new topology of STATCOM, a 1.2 MVAR prototype is built in LAPLACE laboratory and tested on a SNCF test platform
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Schmakat, Philipp [Verfasser], PETER [Akademischer Betreuer] [Gutachter] BOENI, and Winfried [Gutachter] Petry. "Neutron Depolarisation Measurements of Ferromagnetic Quantum Phase Transitions : Wavelength-Frame Multiplication Chopper System for the Imaging Instrument ODIN at the ESS / Philipp Schmakat ; Gutachter: Peter Böni, Winfried Petry ; Betreuer: Peter Böni." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1115332848/34.
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Plogmaker, Stefan. "Techniques and Application of Electron Spectroscopy Based on Novel X-ray Sources." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168799.
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The curiosity of researchers to find novel characteristics and properties of matter constantly pushes for the development of instrumentation based on X-radiation. I present in this thesis techniques for electron spectroscopy based on developments of X-ray sources both in time structure and energy. One part describes a laser driven High-Harmonic Generation source and the application of an off-plane grating monochromator with additional beamlines and spectrometers. In initial experiments, the source is capable of producing harmonics between the 13th and 23rd of the fundamental laser 800 nm wavelength. The intensity in the 19th harmonic, after monochromatization, was measured to be above 1.2·1010 photons/second with a repetition rate of 5 kHz. The development of a chopper system synchronized to the bunch clock of an electron storage ring is also presented. The system can be used to adjust the repetition rate of a synchrotron radiation beam to values between 10 and 120 kHz, or for the modulation of continuous sources. The application of the system to both time of flight spectroscopy and laser pump X-ray probe spectroscopy is shown. It was possible to measure triple ionization of Kr and in applied studies the valence band of a laser excited dye-sensitized solar cell interface. The combination of the latter technique with transient absorption measurements is proposed. The organic molecule maleic anhydride (MA) and its binding configuration to the three anatase TiO2 crystals (101), (100), (001) has been investigated by means of Xray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine structure Spectroscopy (NEXAFS). The results provide information on the binding configuration to the 101 crystal. High Kinetic Energy Photoelectron Spectroscopy was used to investigate multilayers of complexes of iron, ruthenium and osmium. The benefit of hard X-rays for ex-situ prepared samples is demonstrated together with the application of resonant valence band measurements to these molecules.
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Pierleoni, Enrico. "Analisi e progetto del Z-Source Buck Converter." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16305/.
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I convertitori elettronici di potenza operanti in commutazione generalmente operano a partire da sorgenti o di tensione o di corrente. Recentemente si sono studiati convertitori che all’ingresso includono una rete puramente reattiva e priva di perdite (un filtro) in grado di modificare l’impedenza di uscita della sorgente di potenza. L’introduzione di questa rete amplia il numero di configurazioni possibili per gli interruttori del convertitore, dato che l’impedenza di sorgente impedisce le distruttive sovracorrenti legate ai possibili stati di Shoot-Through che, anzi, diventano utili per generare il boost della tensione in ingresso. Poiché le forme d’onda e il modo di funzionamento subiscono drastici cambiamenti, a questo tipo di conversione ci si riferisce con il termine Z-Source.
In questa tesi prenderemo in considerazione la forma più elementare di convertitore dc-dc (il leg commutatore del Chopper‑Buck) e vedremo come l’applicazione della Z-Source consenta una conversione di tensione di tipo salita/discesa, a patto di modificare opportunamente la generazione dei comandi agli interruttori.
Si è potuto verificare a simulazione che il convertitore è effettivamente in grado di operare sia in salita che in discesa.
La complessità delle forme d’onda generate però è tale che è quasi impossibile evitare la comparsa di stati indesiderati non appena si esce dal funzionamento nominale di corrente sul carico o per variazioni dei Duty-cycle dei comandi.
In particolare, si sono riscontrate possibili instabilità che possono far aumentare indefinitamente la tensione sui condensatori del Z‑Source portandola a livelli pericolosamente alti. Inoltre, la presenza del diodo di free-wheeling sull’interruttore low-side può provocare imprevisti stati di Shoot-Through che modificano il Duty‑cycle effettivo in uscita, rendendo di non facile predicibilità il guadagno di tensione del convertitore.
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Nøland, Jonas Kristiansen. "A New Paradigm for Large Brushless Hydrogenerators : Advantages Beyond the Static System." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-317780.
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The grid code, FIKS, from the Norwegian transmission system operator (TSO), Statnett, states that synchronous generators > 25MVA, must have a static excitation system. However, an improved brushless excitation system is in operation on some commercial power plants (36MVA, 93.75rpm & 52MVA, 166.67rpm) with grid-assisting performance beyond the conventional static system. The convenional diode bridge is replaced with a remote-controlled thyristor bridge on the shaft. If wireless communication is not allowed, a control signal through brushes should be employed instead. The thesis explores the expected new era for large brushless hydrogenerators. The proposed brushless system have benefits of reduced regular maintenance due to elimination of brushes and reduced unscheduled maintenance due to redundancy; causing a redused cost-of-energy. A six-phase exciter design with a hybrid-mode thyristor bridge interface leads to improved fault-tolerance, better controllability, minimized torque pulsations and reduced armature currents of the exciter. Excitation boosting (EB) capability is included in the brushless system without additional components or circuitry, contrary to the static excitation system. The brushless excitation system is made insensitive to voltage dips in the interconnected grid, causing improved fault ride-through (FRT) capability and power system stabilizer (PSS) actions.
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Pavlík, Ondřej. "Měnič pro malý 3f asynchronní motor." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219915.
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The aim of this diploma thesis is to continue in prototype realization and a final proposition of three-phase frequency transformer pilot projected in scope of my bachelor work. This transformer is outlined for a small unsynchronized engine to 100 watt output and is designed to supply the fan motor. This suggestion was optimalized from the standpoint of bargain low price and technical feasibility. Powerful part of transformer is solved with help of circuit FSB50450 which is fed from compact source MYRRA 47155. Steering system is guaranteed with circuit MC3PHAC. This device is possible to use in less demanding applications where it was resisted by high expensive price of common frequency transformers.
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Balasubramanian, Sidharth. "Low-voltage and low-power libraries for Medical SoCs." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259776639.
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Gomes, Evandro de Carvalho. "PROJETO DE CONTROLADORES PARA CONVERSORES CC-CC PELA ABORDAGEM DO DESACOPLAMENTO DE ESTADOS." Universidade Federal do Maranhão, 2009. http://tedebc.ufma.br:8080/jspui/handle/tede/422.
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Previous issue date: 2009-09-11In this work, we propose to analyze the controller design of a classical dc-dc converter in a different manner. Instead of the traditional mathematics transfer function analysis, we will describe the block diagram of the plant to be controlled using Space-State Averaging, decoupling the states effects one acts each other and designing the controllers individually. With this technique, we can obtain first order transfer function allowing easier synthesis and design of the involved controllers. Outcomes are compared to controllers based on K-factor approach which are entirely applicable in academy and industry environment.
Neste trabalho propomos analisar o projeto de controladores para conversores cc-cc clássicos de uma forma diferente da tradicional análise matemática da função de transferência, descrevendo o diagrama de blocos da planta a ser controlada, desacoplando os efeitos que um estado exerce sobre o outro e projetando os controladores individualmente. Com essa técnica, obtêm-se funções de transferências de primeira ordem o que permite um projeto e síntese mais fácil dos controladores envolvidos. Os resultados são comparados com os controladores baseados na abordagem do fator K, por se tratar de uma abordagem amplamente aplicada no meio acadêmico e industrial.
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Kauffmann, Claude. "Conception et optimisation d'une alimentation de puissance pour fauteuil roulant électrique : un microcontrôleur régit la commande optimale qui s'adapte au handicap." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL021N.
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L'étude du fauteuil roulant électrique qui redonne une certaine autonomie aux grands handicapés moteurs fait l'objet de ce mémoire. Cette optique nous a amené à traiter le système dans sa globalité: du capteur de conduite a la structure de l'électronique de puissance, en passant par l'électronique de commande numérique et des algorithmes implantés. Un de ces algorithmes met en œuvre une commande optimale robuste de type P. I. D. Qui utilise des méthodes de l'automatique actuelle mais qui reste simple dans sa réalisation en satisfaisant les exigences imposées. Bien que la conception du dispositif développé fait appel à des techniques électroniques évoluées, son cout reste néanmoins très abordable dans le domaine d'utilisation. Cette structure de commande a été validée par : une simulation qui intègre les paramètres réels de l'installation; la réalisation d'un prototype fonctionnel à partir d'un châssis standard de fauteuil roulant. La particularité qui a oriente notre travail vers la conception d'un système à caractère évolutif est la volonté de personnaliser le fauteuil en l'adaptant au handicap de l'utilisateur. Les moyens mis en œuvre ainsi que les perspectives de recherche sont exposés dans ce mémoire
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Kristiansson, Fredric. "Torn, Spun and Chopped : Various Limits of String Theory." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3930.
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Klauss, Catherine Ellen. "Measuring Velocities in an Atom Interferometer Using Chopped Electric Fields." Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144542.
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Böhnke, Dietmar. "Liz Lochhead, 'Mary Queen of Scots Got Her Head Chopped Off' (1987)." Wissenschaftlicher Verlag, 2006. https://ul.qucosa.de/id/qucosa%3A32035.
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Winsryg, Margaret Diggles 1952. "UTILIZATION OF CHOPPED WHEAT STRAW IN COMPLETE RATIONS FOR LACTATING DAIRY COWS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276446.
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Mansouri, Abdelkader. "Le moteur asynchrone monophase à vitesse variable : modélisation et alimentation par convertisseurs statiques." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL096N.
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L’objet de nos travaux concerne la modélisation et l'alimentation par convertisseur statique continu-alternatif et alternatif-alternatif des moteurs asynchrones monophasés à condensateur. Dans la première partie de ce mémoire, nous décrivons un modèle de type circuit incluant les harmoniques d'espace. Afin de dégager l'influence du couplage autre que par le fondamental, nous avons calculé les paramètres de ce modèle à partir des dimensions mécaniques d'un moteur. Après avoir effectué une identification expérimentale des grandeurs correspondant au modèle réduit au fondamental, nous avons simulé le comportement de la machine en régime permanent et en régime transitoire. En vue de régler la vitesse avec de bonnes performances sur le couple, nous avons réalisé un onduleur de tension à fréquence variable. La commande des transistors de puissance constituant ce convertisseur est réalisée au moyen d'un microcontrôleur et suivant un algorithme reposant sur une loi de modulation de largeur d'impulsion à trois niveaux. Le coût étant un critère capital dans les applications à la domotique, nous avons d'abord analyse la commande en vitesse de la machine alimentée par un gradateur à triac ; la machine est trop bruyante. C’est pourquoi nous proposons une alimentation de type hacheur à interrupteur bidirectionnel qui permet d'éliminer ce défaut
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Kuzdas, Jan. "Pomocné měniče v systémech elektrické trakce." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217888.
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The purpose of this thesis is proposal of auxiliary power sources in electric traction. Specifically we deal with two converters. Both of them were used in traction vehicle's applications, which are developed by the Department of Power Electrical and Electronic Engineering, Brno University of Technology. First converter was used as a power supply in secondary traction mechanism of electric locomotive. Second one to power supply of dash board in automobile with fuel cells.
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Fazio, James A. "Durability of Chopped FiberReinforced Polymeric Composites for use in Experimental Automotive Fuel Cells." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/46070.
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Recent interest in utilizing hydrogen fuel cell technology for automotive applications has lead to concerns regarding the durability of fiber reinforced polymer (FRP) composite materials. Automotive fuel cell power train systems must prove themselves as a reliable alternative to the combustion engines and automatic transmissions. The use of polymer composites in fuel cells to serve as manifolds is promising because of their high strength to weight ratio, and they do not corrode like metals manifolds. Composite materials designed for use in Polymer Electrolyte Membrane (PEM) Fuel Cells are exposed to very high humidity environment and operated at elevated temperatures (~85°C). The susceptibility of fiber reinforced polymers to reduction in modulus, strength, and life in chemical environments has been well documented in the literature, especially at elevated temperatures.
A chopped carbon fiber epoxy composite (Material A) and a chopped glass fiber epoxy composite (Material B) were exposed at 85°C to air, water, and a 50/50 water/antifreeze mixture, and periodically examined for tensile, compression, and flexural strengths at various temperatures. Following 2000 hours (83 days) of exposure, Materials A & B did not reach full saturation. Fatigue tests were conducted at various load levels and temperatures to determine their effect on cycles to failure, and carpet plots were generated. Blister formation in aged composites led to reductions in material properties as great as 25% to 75%. A mechanistic explanation was developed for the formation of blisters in the epoxy composite. Recommendations for material improvement and feasibility of material use for fuel cell manifolds and pressure plates were made.
Master of Science
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Heil, Joshua W. "Methods of Processing Kenaf Chopped Strand Mats for Manufacturing Test Specimens and Composite Structures." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4376.
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Bio-composites are increasing in demand due to governmental incentives across the globe for both environmental and human health reasons. The ideal bio-composite is renewable, recyclable, available, and non-toxic. To properly engineer bio-composite products, the physical properties of the fiber as well as fiber/matrix interactions must be known. The problem lies in the fact that many suitable natural fibers are not currently available in a material form that may be easily worked with. This research investigates methods to process raw kenaf (hibiscus cannabinus) on a scale that allows researchers to make more consistent samples for testing. Though kenaf is highlighted, these processing methods may be applied to any natural fiber. The raw fibers are processed into kenaf chopped strand mats (KCSM) by adapting basic paper-making techniques. KCSM exhibit paper-like qualities and mechanical properties and provide a material of uniform thickness for use in composite parts. Also presented are a basic understanding of natural fiber constituents and effects of mechanical and co-mechanical treatments on those constituents. To test KCSM, samples are made for the ASTM D3039 tensile testing and for testing in a dynamic material analyzer (DMA). Both mechanically and chemo-mechanically processed samples are made for the purpose of comparison. Also, I-beam bridges are built with KCSM to demonstrate how KCSM may be used to create a structure. This is spurred on by the annual SAMPE bridge competition that includes special categories for natural fiber beams. The lay-up procedure is shown in detail to provide a framework that future competitors may use to build quality I-beams for this competition.
The properties obtained by using the KCSM are competitive with other reported properties for kenaf-based composites. A kenaf I-beam demonstrates a strength-to-weight ratio that is 65% of a berglass I-beam built to the same dimensions. Trade-os of using KCSM are the random 2d-fiber orientation and brittle failure, which are not usually desirable in composite components. The chemically treated samples indicate a higher degree of crystallinity but demonstrate inferior mechanical properties when compared to the untreated samples.
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Zein, El Din Ashraf. "Comparaison d'architecture pour la commande des machines électriques." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL034N.
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La numérisation systématique des systèmes de commande des machines électriques peut apporter: stabilité, évolutivité, aptitude à la communication et à l'amélioration de la sureté de fonctionnement. Cependant, les contraintes posées par ce domaine spécifique (contraintes de temps en particulier) ont limité le recours massif aux microprocesseurs. Certains composants aujourd'hui disponibles peuvent apporter des solutions intéressantes à ces problèmes. Aussi, dans un premier chapitre, la thèse présente un catalogue comparatif de ces produits: microprocesseurs, RISC, CISC, microcontroleurs, DSP, ASIC, transputers. . . Le second chapitre est une étude bibliographique donnant quelques exemples dans le domaine des machines électriques en utilisant ces différents produits. Dans le troisième chapitre, la thèse présente un circuit ASIC conçu a l'Ensem. Ce circuit a été spécialement conçu pour la commande d'un demi-pont de thyristors. Ainsi, il a été utilisé conjointement à un microcontrôleur pur la commande d'un hacheur. Le rôle du microcontrôleur est de fournir à l'ASIC le taux de modélisation désiré, compte tenu du courant et de la vitesse. Le chapitre suivant montre l'utilisation du même microcontrôleur pour la commande d'un cyclo-convertisseur. Après avoir décrit l'électronique d'interface du système, l'algorithme de commande est décrit avec la méthode marel. L'auteur montre que la puissance du microcontrôleur est suffisante pour la commande d'un cycloconvertisseur triphasé, mais pour des raisons de sureté, il recommande plutôt l'emploi d'un microcontrôleur par phase. En conclusion, il recommande pour l'avenir de ne pas hésiter à recourir aux solutions multiprocesseurs spécialisés, chaque type pouvant apporter une solution à un problème ponctuel avec des performances optimales
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Bahmer, Andreas. "Computer simulation of chopper neurons." Phd thesis, 2007. https://tuprints.ulb.tu-darmstadt.de/817/1/Promotion_bahmer.pdf.
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The aim of this work was to test a new model for oscillating neurons (chopper neurons) in the cochlear nucleus of the auditory system. In the beginning, it is shown that multiples of 0.4 ms are apparent in intrinsic oscillations in the auditory system and in pitch shift experiments. The existence of a time constant of 0.4 ms is explained by the assumption of a minimum chemical synaptic delay of this size between chopper neurons. The large dynamic range of periodicity coding, the small dynamic range of pure tone response, and the sharp frequency tuning of chopper neurons can be explained as a functional result of simultaneous projections from both the auditory nerve fibers and onset neurons to chopper neurons. As a consequence, the topology of the simulation of chopper neurons is as follows: To ensure the preference for multiples of 0.4 ms as observed in physiological and psychophysical experiments, chopper neurons are arranged in a circular network. The minimum number of two chopper neurons in this network results in a chopper period of 0.8 ms which corresponds to the proposed minimum refractory period of 0.8 ms. In the topology, chopper neurons receive input from both auditory nerve fibers and onset neurons. Simulations of the model show that in contrast to previous models, the present model can explain the preference for multiples of 0.4 ms. The model has also the advantage of explaining their large dynamic range of periodicity encoding of chopper neurons in spite of their narrow frequency tuning. Like the models investigated previously by other authors, the present model is able to simulate interspike intervals of spike trains of the chopper responses with high precision. Moreover, the simulation can explain essential properties of real chopper neurons by input from onset neurons. Simulations of the chopper neurons show that variation of the integration widths of onset neurons results in a corresponding variation of the spectral resolution of chopper neurons with smaller widths resulting in a higher resolution of frequency components. Variation of the integration widths of onset neurons also results in variation of the periodicity encoding of chopper neurons. Narrow integration widths lead to better periodicity encoding at low levels. At high levels broader integration widths lead to better periodicity encoding. Therefore it is a conflicting demand at high levels for to adapt the width of the integration to tuning or to encoding periodicity. The observed pitch dichotomy of individual preferences of human subjects for either periodicity pitch or the pitch of low spectral components of harmonic sounds (Schneider et al., 2005) can be explained by assuming adaptations of the width of the integration to either spectral or temporal coding. In contrast to physiological data, Hodgkin-Huxley(HH)-like models of single chopper neurons (e.g. from Rothman and Manis, 2003c) show a strong dependency of their interspike intervals when changing the input strength and do not show any preference for multiples of 0.4 ms. My simulations show that networks of HH-like chopper neurons with a synaptic delay of 0.4 ms do exhibit this preference and their chopper intervals are independent of changing the input strength. The HH-like model of chopper neurons by Rothman and Manis (2003c) does not account for short oscillating intervals of real chopper neurons. The model has been modified with genetic algorithms to generate oscillating intervals as short as 0.8 ms. This "fast Rothman chopper" has been successfully integrated in simulation topology. An enlarged network which is synchronized by a circuit of two "fast Rothman choppers" can account for a preference of ISIs for multiples of 0.4 ms as found in physiological data.
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Faizy, A., and S. Kumar. "DC Motor Control using Chopper." Thesis, 2010. http://ethesis.nitrkl.ac.in/1677/2/amir_final_project_report.pdf.
Full textAbstract:
The speed of separately excited DC motor can be controlled from below and up to rated speed using chopper as a converter. The chopper firing circuit receives signal from controller and then chopper gives variable voltage to the armature of the motor for achieving desired speed. There are two control loops, one for controlling current and another for speed. The controller used is Proportional-Integral type which removes the delay and provides fast control. Modeling of separately excited DC motor is done. The complete layout of DC drive mechanism is obtained. The designing of current and speed controller is carried out. The optimization of speed controller is done using modulus hugging approach, in order to get stable and fast control of DC motor. After obtaining the complete model of DC drive system, the model is simulated using MATLAB(SIMULINK).The simulation of DC motor drive is done and analyzed under varying speed and varying load torque conditions like rated speed and load torque, half the rated load torque and speed, step speed and load torque and stair case load. torque and speed.
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Cheng, Lan-Shan, and 鄭嵐瑄. "Design of CMOS Chopper Temperature Sensor." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/61364617988166674644.
Full textAbstract:
碩士國立清華大學
電子工程研究所
92
A CMOS chopper temperature sensor is present. Accurate bandgap reference and PTAT voltage are designed. The circuit uses substrate bipolar transistors as a temperature sensing element. In order to reduce the effect of the offset voltage of the operational amplifier in the circuit, we use the chopper stabilization technique to eliminate the offset voltage. The complete system is realized in a double metal 0.6�慆 CMOS process, and the chip size is 1.3mm2. In the temperature range from -55 to 125�aC, the total inaccuracy of bandgap reference and PTAT voltage is 3.5�aC without calibration. The circuit operates at a typical supply voltage, 3.3V, and its supply current is 150�嫀. Experiment results of the bandgap reference and PTAT voltage and simulated design of the circuit are discussed in this thesis.
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Deepak, M. L., and A. Mishra. "Speed control of DC motorusing chopper." Thesis, 2014. http://ethesis.nitrkl.ac.in/5954/1/E-121.pdf.
Full textAbstract:
DC motors form the backbone of many industries and as such their speed control becomes of immense importance. It has been found that many of these applications perform with a greater efficiency when the motors are fed from a source of variable dc power. In this report we analyze the separately excited dc motor using, MATLAB (Simulink), for speeds above and below the rated speed using a chopper circuit. The chopper circuit receives a signal from the firing circuit and then gives a signal to the armature voltage controller of the separately excited dc motor and the speed is accordingly increased or decreased. In this system we use two different control loops, in for speed and another for current. Here we use a proportional integral type control as in this the delay gets removed and the control provided is very fast. The dc motor is modelled and the control loops are laid out and then onwards we design the drive system. There after the simulations of the system have been carried out and analyzed under varying circumstances of speed and load torque.