Tesi sul tema "Transmission Devices"

ERICSSON DO BRASIL
A utilização de transformadores de impedância banda larga possibilita o acoplamento de forma eficiente das linhas convencionais de 50 (ômegas) dos sistemas de alta freqüência aos componentes optoeletrônicos de alta velocidade de baixa impedância, tais como lasers semicondutores (tipicamente com 3 a 5 (ômegas) de resistência de entrada). Uma das principais restrições para a realização de um transformador de impedância planar para uso em sistemas de comunicações ópticas é a sua dimensão física. A fim de se obter um transformador de impedância compacto, de dimensões compatíveis com às dos dispositivos optoeletrônicos, foram analisadas diferentes configurações. Inicialmente foi analisada a configuração coplanar (CPW) utilizando substrato de altíssima constante dielétrica. Devido às limitações encontradas nesta configuração, são propostas, aqui, duas outras soluções. As duas novas configurações propostas associam ao substrato bulk convencional de alumina, filmes de elevada constante dielétrica. Foi desenvolvida uma técnica para caracterizar a constante dielétrica e as perdas dos filmes especialmente fabricados para este trabalho. As análises teóricas mostraram que as configurações propostas apresentam desempenho muito superior ao desempenho das configurações convencionais CPW. Foi implementado o transformador de impedância utilizando uma das soluções propostas e seu desempenho foi avaliado experimentalmente.
Wide-band transmission line impedance transformer enables efficient coupling of 50 (ômegas) transmission line circuits to low impedance high-speed optoelectronic components such as semiconductor lasers (typically with input resistance of 3 to 5 [ômegas]). The physical dimensions of the planar transmission line transformer have to be properly chosen to allow its use in optical communication systems. In order to design a high performance impedance transformer with physical dimensions compatible with optoelectronic components, several possibilities were investigated. A CPW configuration with very high dielectric constant bulk substrate has been analyzed. Simulations have shown some limitations in the performance of this configuration. Then, two new configurations were introduced. Both configurations are obtained using high dielectric constant films and alumina bulk substrate. A new technique has been developed in order to characterize the dielectric constant and the losses of the films specially made for this thesis. Simulations have shown that the performance of both new configurations is much better than the conventional CPW configuration performance. The planar transmission line impedance transformer has been constructed using a new configuration and its performance has been experimentally evaluated.

With the rapid growth and use of wearable devices over the last decade, the advantages of using portable wearable devices are now been utilised for day to day activities. These wearable devices are designed to be flexible, low profile, light-weight and smoothly integrated into daily life. Wearable transmission lines are required to transport RF signals between various pieces of wearable communication equipment and to connect fabric based antennas to transmitters and receivers; the stitched transmission line is one of the hardware solutions developed to enhance the connectivity between these wearable devices. Textile manufacturing techniques that employ the use of sewing machines alongside conductive textile materials can be used to fabricate the stitched transmission line. In this thesis the feasibility of using a sewing machine in fabrication of a novel stitched transmission line for wearable devices using the idea of a braided coaxial cable have been examined. The sewing machine used is capable of a zig-zag stitch with approximate width and length within the range of 0-6 mm and 0-4mm respectively. The inner conductor and the tubular insulated layer of the stitched transmission lines were selected as RG 174, while the stitched shields were made up of copper wires and conductive threads from Light Stiches®. For shielding purpose, the structure is stitched onto a denim material with a conductive thread with the aid of a novel manufacturing technique using a standard hardware. The Scattering Parameters of the stitched transmission line were investigated with three different stitch angles 85°, 65° and 31° through simulation and experiments, with the results demonstrating that the stitched transmission line can work usefully and consistently from 0.04 to 4GHz. The extracted Scattering parameters indicated a decrease in DC loss with increased stitch angle and an increase in radiation loses, which tends to increase with increase in frequency. The proposed stitched transmission line makes a viable transmission line but a short stitch length is associated with larger losses through resistance. The DC losses observed are mainly influenced by the resistance of the conductive threads at lower frequencies while the radiation losses are influenced by the wider apertures related to the stitch angles and increase in frequency along the line. The performances of the stitched transmission line with different stitch patterns, when subjected to washing cycles and when bent through curved angles 90° and 180° were also investigated and results presented. Also, the sensitivity of the design to manufacturing tolerances was also considered. First the behaviour of the stitched transmission line with two different substrates Denim and Felt were investigated with the results indicating an insignificant increase in losses with the Denim material. Secondly, the sensitivity of the design with variations in cross section dimensions was investigated using numerical modelling techniques and the results showed that the impedance of the stitched transmission line increases when the cross sectional dimensions are decreased by 0.40mm and decreases when the cross sectional dimensions are increased by 0.40mm. Equally, repeatability of the stitched transmission line with three different stitch angles 85°, 65° and 31° were carried out. The results were seen to be consistent up to 2.5GHz, with slight deviations above that, which are mainly as a result of multiple reflections along the line resulting in loss ripples. The DC resistance of the stitched transmission line with three different stitch angles 85°, 65° and 31° corresponding to the number of stitches 60,90 and 162 were computed and a mathematical relationship was derived for computing the DC resistance of the stitch transmission line for any given number of stitches. The DC resistance computed results of 25.6Ω, 17.3Ω and 13.1Ω, for 31°, 65° and 85° stitch angles, indicated an increase in DC resistance of the stitch with decrease in stitch angle which gives rise to an increase in number of stitches. The transfer impedance of the stitched transmission line was also computed at low frequency (< 1GHz) to be ZT=(0.24+j1.09)Ω, with the result showing the effectiveness of the shield of the stitched transmission line at low frequency (< 1GHz).

The main tasks of power electronics in power transmission and distribution systems is to process and control the flow of electric energy by supplying voltages and currents in a form that is suitable for user loads. In recent years, the field of power electronics has experienced a large growth. Electric utilities expected that by the year 2000 over half of the electrical load may be supplied through power electronic systems. In order to take advantage of this highly developed technology a number of detailed modelling procedures and simulation facilities are needed. The work in this thesis is concentrated on modelling, control and design of various power electronic based models for use within transmission and distribution systems. The overall objective is to provide effective methods and tools for assessing the impact of the latest technology based on power electronic devices in the reinforcement of power system networks. The thesis clarifies modelling and control of various variable speed drive models, such as the six-step, PWM and vector control and gives a detailed account of the systematic derivation of equations that are necessary for the dynamic and transient analysis of a multi-machine multi-node power system with associated adjustable speed drives. Simulation of Flexible AC Transmission Systems (FACTS) models has also been developed for a number of devices including: the SVC (Static Var Compensator), the STATCON (Static Condenser) and the UPFC (Unified Power Flow Controller). The methodologies for development of the models are described and a number of case studies are included in order to give a broad overview of the applications and to prove the usefulness of the results. The last part of the thesis includes simulation, control and design of Custom Power Devices for use within distribution system architectures. It starts with a complete control system strategy for the modelling of a solid-state switch and continues with the modelling of a Dynamic Voltage Restorer model, using an innovative control system. The creation of the power electronics models library provides several opportunities for future developments, which are discussed in the concluding sections of the thesis.

This thesis describes the implementation of the Flexible AC Transmission Systems (FACTS) devices to develop a market-based approach to the problem of transmission congestion management in a Balancing Market. The causes, remedies and pricing methods of transmission congestion are briefly reviewed. Balancing Market exists in markets in which most of the trading is done via decentralized bilateral contracts. In these markets only final adjustments necessary to ensure secure system operation is carried out at a centralized Balancing Market. Each market player can participate in the Balancing Market by submitting offers and bids to increase and decrease its initially submitted active generation output. In this research a method is proposed to reduce costs associated with congestion re-dispatch in a Balancing Market by optimal placement of FACTS devices, and in particular Thyristor Controlled Phase Shifter Transformers (TCPST). The proposed technique is applicable to both Mixed Integer Linear Programming (MILP) and Mixed Integer Non-Linear Programming (MINLP). In the MILP a power system network is represented by a simplified DC power flow under a MILP structure and the Market participants' offers and bids are also represented by linear models. Results show that applications of FACTS devices can significantly reduce costs of congestion re-dispatch. The application of the method based on the MINLP creates a nonlinear and non-convex AC OPF problem that might be trapped in local sub-optima solutions. The reliability of the solution that determines the optimal placement of FACTS devices is an important issue and is carried out by investigation of alternative solvers. The behavior of the MINLP solvers is presented and finally the best solvers for this particular optimization problem are introduced. The application of DC OPF is very common in industry. The accuracy of the DC OPF results is investigated and a comparison between the DC and AC OPF is presented.

Multimedia transmission is the effective way of transmitting multimedia elements (comprising voice, audio, video, data etc) from one place to the other via internet enabled protocols and other means. The term 'effective' is used because multimedia transmission is a nightmare if the conveyance is not smooth, seamless and efficient. Over time, the world has seen tremendous improvement that started from the era of the first generation of multimedia generation to the point of multimedia transmission. Much has been said and done in this area and the world has become a connected enterprise because of the transmission of multimedia. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols.
Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

Emerging body-wearable sensor devices for continuous health monitoring are severely energy constrained and yet required to offer high communication reliability under fluctuating channel conditions. This thesis aims at investigating the opportunities and challenges in the use of dynamic radio transmit power control for prolonging the lifetime of such devices. We first present extensive empirical evidence that the wireless link quality can change rapidly in body area networks, and a fixed transmit power results in either wasted energy (when the link is good) or low reliability (when the link is bad). We then propose a class of schemes feasible for practical implementation that adapt transmit power in real-time based on feedback information from the receiver. We show conservative, balanced, and aggressive adaptations of our scheme that progressively achieve higher energy savings of 14%-30% in exchange for higher potential packet losses (up to 10%). We also provide guidelines on how the parameters can be tuned to achieve the desired trade-off between energy savings and reliability within the chosen operating environment. Finally, we implement and profile our scheme on a MicaZ mote based platform, demonstrating that energy savings are achievable even with imperfect feedback information, and report preliminary results on the ultra-low-power integrated healthcare monitoring platform from our collaborating partner Toumaz Technology. In conclusion, our work shows adaptive radio transmit power control as a low-cost way of extending the battery-life of severely energy constrained body wearable devices, and opens the door to further optimizations customized for specific deployment scenarios.

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.

Multi band technology helps in getting multiple operating frequencies using a single microwave device. This thesis presents the design of dual and tri band microwave devices using coupled transmission line structures. Chapter 2 presents the design of a novel dual band transmission line structure using coupled lines. In chapter 3, Design of a dual band branch line coupler and a dual band Wilkinson power divider are proposed using the novel dual band transmission line structure presented in the previous chapter. In chapter 4, Design of a tri band transmission line structure by extending the dual band structure is presented. The Conclusion and future work are presented in chapter 5.

This thesis presents a theoretical investigation on applications of Raman effect in optical fibre communication as well as the design and optimisation of various Raman based devices and transmission schemes. The techniques used are mainly based on numerical modelling. The results presented in this thesis are divided into three main parts. First, novel designs of Raman fibre lasers (RFLs) based on Phosphosilicate core fibre are analysed and optimised for efficiency by using a discrete power balance model. The designs include a two stage RFL based on Phosphosilicate core fibre for telecommunication applications, a composite RFL for the 1.6 μm spectral window, and a multiple output wavelength RFL aimed to be used as a compact pump source for fiat gain Raman amplifiers. The use of Phosphosilicate core fibre is proven to effectively reduce the design complexity and hence leads to a better efficiency, stability and potentially lower cost. Second, the generalised Raman amplified gain model approach based on the power balance analysis and direct numerical simulation is developed. The approach can be used to effectively simulate optical transmission systems with distributed Raman amplification. Last, the potential employment of a hybrid amplification scheme, which is a combination between a distributed Raman amplifier and Erbium doped amplifier, is investigated by using the generalised Raman amplified gain model. The analysis focuses on the use of the scheme to upgrade a standard fibre network to 40 Gb/s system.

D’importants progès ont été réalisés dans le développement des systèmes biomédicaux implantables grâce aux dernières avancées de la microélectronique et des technologies sans fil. Néanmoins, ces appareils restent difficiles à commercialier. Cette situation est due particulièrement à un manque de stratégies de design capable supporter les fonctionnalités exigées, aux limites de miniaturisation, ainsi qu’au manque d’interface sans fil à haut débit fiable et faible puissance capable de connecter les implants et les périphériques externes. Le nombre de sites de stimulation et/ou d’électrodes d’enregistrement retrouvés dans les dernières interfaces cerveau-ordinateur (IMC) ne cesse de croître afin d’augmenter la précision de contrôle, et d’améliorer notre compréhension des fonctions cérébrales. Ce nombre est appelé à atteindre un millier de site à court terme, ce qui exige des débits de données atteingnant facilement les 500 Mbps. Ceci étant dit, ces travaux visent à élaborer de nouvelles stratégies innovantes de conception de dispositifs biomédicaux implantables afin de repousser les limites mentionnées ci-dessus. On présente de nouvelles techniques faible puissance beaucoup plus performantes pour le transfert d’énergie et de données sans fil à haut débit ainsi que l’analyse et la réalisation de ces dernières grâce à des prototypes microélectroniques CMOS. Dans un premier temps, ces travaux exposent notre nouvelle structure multibobine inductive à résonance présentant une puissance sans fil distribuée uniformément pour alimenter des systèmes miniatures d’étude du cerveaux avec des models animaux en ilberté ainsi que des dispositifs médicaux implantbles sans fil qui se caractérisent par une capacité de positionnement libre. La structure propose un lien de résonance multibobines inductive, dont le résonateur principal est constitué d’une multitude de résonateurs identiques disposés dans une matrice de bobines carrées. Ces dernières sont connectées en parallèle afin de réaliser des surfaces de puissance (2D) ainsi qu’une chambre d’alimentation (3D). La chambre proposée utilise deux matrices de résonateurs de base, mises face à face et connectés en parallèle afin d’obtenir une distribution d’énergie uniforme en 3D. Chaque surface comprend neuf bobines superposées, connectées en parallèle et réailsées sur une carte de circuit imprimé deux couches FR4. La chambre dispose d’un mécanisme naturel de localisation de puissance qui facilite sa mise en oeuvre et son fonctionnement. En procédant ainsi, nous évitons la nécessité d’une détection active de l’emplacement de la charge et le contrôle d’alimentation. Notre approche permet à cette surface d’alimentation unique de fournir une efficacité de transfert de puissance (PTE) de 69% et une puissance délivrée à la charge (PDL) de 120 mW, pour une distance de séparation de 4 cm, tandis que le prototype de chambre complet fournit un PTE uniforme de 59% et un PDL de 100 mW en 3D, partout à l’intérieur de la chambre avec un volume de chambre de 27 × 27 × 16 cm3. Une étape critique avant d’utiliser un dispositif implantable chez les humains consiste à vérifier ses fonctionnalités sur des sujets animaux. Par conséquent, la chambre d’énergie sans fil conçue sera utilisée afin de caractériser les performances d’ une interface sans fil de transmisison de données dans un environnement réaliste in vivo avec positionement libre. Un émetteur-récepteur full-duplex (FDT) entièrement intégré qui se caractérise par sa faible puissance est conçu pour réaliser une interfaces bi-directionnelles (stimulation et enregistrement) avec des débits asymétriques: des taux de tramnsmission plus élevés sont nécessaires pour l’enregistrement électrophysiologique multicanal (signaux de liaison montante) alors que les taux moins élevés sont utilisés pour la stimulation (les signaux de liaison descendante). L’émetteur (TX) et le récepteur (RX) se partagent une seule antenne afin de réduire la taille de l’implant. L’émetteur utilise la radio ultra-large bande par impulsions (IR-UWB) basée sur l’approche edge combining et le RX utilise la bande ISM (Industrielle, Scientifique et Médicale) de fréquence central 2.4 GHz et la modulation on-off-keying (OOK). Une bonne isolation (> 20 dB) est obtenue entre le TX et le RX grâce à 1) la mise en forme les impulsions émises dans le spectre UWB non réglementée (3.1-7 GHz), et 2) le filtrage espace-efficace (évitant l’utilisation d’un circulateur ou d’un diplexeur) du spectre du lien de communication descendant directement au niveau de l’ amplificateur à faible bruit (LNA). L’émetteur UWB 3.1-7 GHz utilise un e modultion OOK ainsi qu’une modulation par déplacement de phase (BPSK) à seulement 10.8 pJ / bits. Le FDT proposé permet d’atteindre 500 Mbps de débit de données en lien montant et 100 Mbps de débit de données de lien descendant. Il est entièrement intégré dans un procédé TSMC CMOS 0.18 um standard et possède une taille totale de 0.8 mm2. La consommation totale d’énergie mesurée est de 10.4 mW (5 mW pour RX et 5.4 mW pour TX au taux de 500 Mbps).
In recent years, there has been major progress on implantable biomedical systems that support most of the functionalities of wireless implantable devices. Nevertheless, these devices remain mostly restricted to be commercialized, in part due to weakness of a straightforward design to support the required functionalities, limitation on miniaturization, and lack of a reliable low-power high data rate interface between implants and external devices. This research provides novel strategies on the design of implantable biomedical devices that addresses these limitations by presenting analysis and techniques for wireless power transfer and efficient data transfer. The first part of this research includes our proposed novel resonance-based multicoil inductive power link structure with uniform power distribution to wirelessly power up smart animal research systems and implanted medical devices with high power efficiency and free positioning capability. The proposed structure consists of a multicoil resonance inductive link, which primary resonator array is made of several identical resonators enclosed in a scalable array of overlapping square coils that are connected in parallel and arranged in power surface (2D) and power chamber (3D) configurations. The proposed chamber uses two arrays of primary resonators, facing each other, and connected in parallel to achieve uniform power distribution in 3D. Each surface includes 9 overlapped coils connected in parallel and implemented into two layers of FR4 printed circuit board. The chamber features a natural power localization mechanism, which simplifies its implementation and eases its operation by avoiding the need for active detection of the load location and power control mechanisms. A single power surface based on the proposed approach can provide a power transfer efficiency (PTE) of 69% and a power delivered to the load (PDL) of 120 mW, for a separation distance of 4 cm, whereas the complete chamber prototype provides a uniform PTE of 59% and a PDL of 100 mW in 3D, everywhere inside the chamber with a chamber size of 27×27×16 cm3. The second part of this research includes our proposed novel, fully-integrated, low-power fullduplex transceiver (FDT) to support bi-directional neural interfacing applications (stimulating and recording) with asymmetric data rates: higher rates are required for recording (uplink signals) than stimulation (downlink signals). The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by space-efficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier (LNA). The UWB 3.1-7 GHz transmitter using OOK and binary phase shift keying (BPSK) modulations at only 10.8 pJ/bit. The proposed FDT provides dual band 500 Mbps TX uplink data rate and 100 Mbps RX downlink data rate. It is fully integrated on standard TSMC 0.18 nm CMOS within a total size of 0.8 mm2. The total power consumption measured 10.4 mW (5 mW for RX and 5.4 mW for TX at the rate of 500 Mbps).

With an increasing number of regulatory and economic factors making the operation of power systems more challenging, utilities must take full advantage of technological advances which allow more flexibility for operation. One of these advances is the combination of power electronic controllers and compensation devices known as F1exible AC Transmission Systems (FACTS) technology. This thesis will examine the ability of FACTS technology to improve dynamic stability when controlled with data obtained from another recent advancement, phasor measurement units (PMUs). Based on an overview of the relative capabilities of presently available FACTS devices, a specific device will be chosen to be modeled in a dynamic stability study. Eigenvalue sensitivity analysis will be used to determine the optimal placement for this FACTS device in regards to stability for a test power system. Then a state space model will be developed for the FACTS compensated test system, and eigenvalue sensitivity and time-domain methods will be used to determine the optimal controller characteristics for the modeled FACTS device. Stability results will be verified using eigenvalue analysis and time simulation techniques.
Master of Science

The uses of flexible alternating current transmission system (FACTS) controllers in next generation smart grids are encouraged by the increased uses of decentralized and highly meshed grid structures that may affect the stability of power systems. Voltage source converter (VSC) based FACTS devices have reduced footprint and offer increased control flexibility, extended range and faster reaction time than line commutated thyristor based equivalent solutions. The performance of commonly used FACTS devices that employ a two-level converter is summarized. Then, multilevel converters and direct AC-AC converters which are viable for FACTS applications are reviewed. The outcomes of the literature surveys are refined to identify new features that may be critical for future centralised and decentralized smart grids such as: control range extension, improved efficiency and power density at reduced hardware cost. To pursue these features, three novel VSC topologies are proposed and analysed: An AC voltage-doubled (ACVD) topology with an internal inverting buck-boost cell in each phase-leg, is able to synthesize twice the output voltage of a conventional two-level VSC for the same dc link voltage, is proposed. A number of new modulation and control strategies that aim to further increase DC utilization of the ACVD converter and to manage its internal dynamic interaction to prevent the appearance of low-order harmonics in the output currents, are presented. With its high DC-rail utilization and sophisticated control strategies, the ACVD converter offers an extended power control range, which is increasingly important for shunt and series type FACTS devices. The controlled transition full-bridge hybrid multilevel converter (CTFB-HMC) with chain-links of full-bridge cells is proposed to combine the advantages of improved wave-shaping ability, reduced footprint and high efficiency, which promote its applications in medium and high voltage FACTS devices. An AC hexagonal chopper using heterodyne modulation to decouple the control of AC voltage amplitude from that of the phase-angle is proposed. For scalability to medium and high voltage, a modular multilevel AC hexagonal chopper (M2AHC) is developed. With adoption of a quasi-two-level transitional mode for reduced cell number and minimized footprint, dv/dt is limited and reliability is improved. Simulation and experimentation are used to validate the modulation, control and FACTS implementation of the three proposed converters.

Recent network technology developments have led to the emergence of a variety of access network technologies - such as IEEE 802.11, wireless local area network (WLAN), IEEE 802.16, Worldwide Interoperability for Microwave Access (WIMAX) and Long Term Evolution (LTE) - which can be integrated to offer ubiquitous access in a heterogeneous network environment. User devices also come equipped with multiple network interfaces to connect to the different network technologies, making it possible to establish multiple network paths between end hosts. However, the current connectivity settings confine the user devices to using a single network path at a time, leading to low utilization of the resources in a heterogeneous network and poor performance for demanding applications, such as high definition video streaming. The simultaneous use of multiple network interfaces, also called bandwidth aggregation, can increase application throughput and reduce the packets' end-to-end delays. However, multiple independent paths often have heterogeneous characteristics in terms of offered bandwidth, latency and loss rate, making it challenging to achieve efficient bandwidth aggregation. For instance, striping the flow's packets over multiple network paths with different latencies can cause packet reordering, which can significantly degrade performance of the current transport protocols. This thesis proposes three new solutions to mitigate the effects of network path heterogeneity on the performance of various concurrent multipath transmission settings. First, a network layer solution is proposed to stripe packets of delay-sensitive and high-bandwidth applications for concurrent transmission across multiple network paths. The solution leverages the paths' latency heterogeneity to reduce packet reordering, leading to minimal reordering delay, which improves performance of delay-sensitive applications. Second, multipath video streaming is developed for H.264 scalable video, where the reference video packets are adaptively assigned to low loss network paths to reduce drifting errors, thus combatting H.264 video distortion effectively. Finally, a new segment scheduling framework - which carefully considers path heterogeneity - is incorporated into the IETF Multipath TCP to improve throughput performance. The proposed solutions have been validated using a series of simulation experiments. The results reveal that the proposed solutions can enable efficient bandwidth aggregation for concurrent multipath transmission over heterogeneous network paths.

Currently, transmission network security is treated within a deterministic and preventive control framework where network constraints and balancing costs are not fully optimised. This may be inefficient and lead to increased levels of congestion, potentially increasing cost of integration associated with low-carbon generation. In this context, this thesis assesses the effects of coordinating FACTS and HVDC transmission systems under both deterministic and probabilistic security frameworks and assuming an array of available preventive/corrective control actions. An deterministic/probabilistic cost-benefit model has been developed for assessing the economic and reliability performance of alternative control strategies enabled by coordination of flexible devices. Results demonstrate that probabilistic security for flexible AC/DC devices coordination is significantly more beneficial since it can lead to lower operating costs, increased infrastructure utilisation and improved reserve allocation across GB network. The framework is further developed to explicitly consider the likelihood of post-contingency events and wind uncertainty. A tight MILP representation, two novelty transmission losses penalty items and scenario reduction model are proposed to reduce computational burden in the large-scale system. Results demonstrate the advantages of probabilistic security to improving the overall efficiency of the system when integrate uncertain renewable generation. Adding flexible network technology could even increase system costs under a preventive security approach. Finally, a novel two-stage stochastic optimization model that incorporates effect of dynamic line rating (DLR) on transmission network operation with increased penetration of wind generation is proposed. The stochastic model co-optimizes energy and reserve holding levels for the forecasted/expected condition along with re-dispatch actions under real-time operation. The benefits of using DLR are demonstrated in terms of overall cost minimization, albeit reserve levels may be increased due to DLR uncertainty. Results also demonstrate that reserve services can be shared among multiple uncertainties. The impacts of forecast accuracy and reserve price on the performance of DLR is discussed.

Les progres recents en nanotechnologie, caracterisation haute frequence and conception assistee par ordinateur ont modifie de maniere importante la fabrication de systemes aux frequences millimetriques et sub-millimetriques. Dans ce contexte, ce travail concerne la simulation electromagnetique de composants actifs et passifs pour des applications spatiales. Trois sujets en relation avec le domaine terahertz, (i) un multiplicateur de frequence employant une heterostructure barriere varactor (hbv), (ii) des microinterrupteurs et lignes de transmission micro-usinees et (iii) des structures a bande interdite photonique metalliques, ont ete specialement etudies. En ce qui concerne la conception du multiplicateur de frequence, de 83 a 250 ghz, notre contribution est basee sur l'analyse electromagnetique du composant actif en tenant compte de son environnement. En partant d'un composant hbv fabrique a l'iemn avec de bonnes performances en termes de rapport de capacite 5:1 et de niveau de capacite sans polarisation, 1 ff/m#2, nous avons etudie l'influence des techniques d'integration sur ses performances
En combinant differentes approches, telles que des techniques de mesure sous pointes, des simulations en equilibrage harmonique et une analyse electromagnetique, nous avons pu analyser un composant integre dans une cellule de multiplication. Par rapport aux composants micro-usines, nous nous sommes interesses, d'une part, a des lignes coplanaires sur membrane, et d'autre part a des microinterrupteurs. Un comportement faibles pertes sans dispersion a ete demontre dans le premier cas jusqu'a 100 ghz, alors que l'on a determine des frequences d'utilisation maximales dans le deuxieme cas. Finalement, notre effort s'est oriente vers l'analyse de structures metalliques periodiques artificielles presentant des bandes interdites electromagnetiques. Ces materiaux a bande interdite photonique sont potentiellement interessants pour des applications millimetriques telles que filtres, elements rayonnants ou de guidage

Dans cette thèse, nous abordons les défis rencontrés lors de la caractérisation des mémoires non volatiles par microscopie en transmission in situ. Les innovations récentes menées sur les porte-objets de TEM in situ basés sur l'utilisation de puces en silicium apportent de grands avantages comparée aux précédents modèles. Cependant, cette technique reste complexe et les expériences de MET in situ sont difficiles à mener à terme. Ce manuscrit tente d'apporter de nouvelles solutions pour permettre l'observation à l'échelle atomique pendant le recuit, ou la polarisation d'un échantillon dans le MET. Ce projet a été mené à travers plusieurs améliorations effectuées au cours des différentes étapes des expériences de MET in situ. Cette thèse se focalise plus particulièrement sur les problèmes rencontrés lors de la polarisation de dispositifs de mémoires résistives de taille nanométrique. Ces travaux furent conduits à travers une étude des instruments utilisés, le développement de nouvelles méthodes de préparation d'échantillons, et une analyse de l'impact de l'imagerie électronique sur le fonctionnement d'un dispositif dans le MET.Tout d’abord, une nouvelle méthode est développée spécifiquement pour les expériences de MET in situ en température. Grâce à ces développements, la cristallisation de mémoires à changement de phase en GeTe est observée en temps réel. Ces résultats ont notamment permis d'obtenir des informations utiles pour le développement de mémoires à changement de phase de type chalcogénure. Ensuite, de nouvelles puces en silicium dédiées à la polarisation in situ sont développées et produites. Une étude est ensuite menée sur la préparation d'échantillons par FIB afin d'améliorer la qualité des contacts électriques pour la polarisation in situ, ainsi que la technique de préparation elle-même. La qualité de cette méthode est ensuite démontrée à travers des mesures quantitatives obtenues pendant la polarisation in situ d'un échantillon de référence de type jonction PN. Ces développements sont ensuite appliqués afin d’observer des dispositifs de mémoires résistives de type CBRAM en fonctionnement dans le microscope électronique en transmission. Ces résultats ont permis d'apporter de nouvelles informations sur les mécanismes de fonctionnement des mémoires résistives, ainsi que sur la technique de polarisation in situ
In this work, we address the current challenges encountered during in situ Transmission Electron Microscopy characterization of emerging non volatile data storage technologies. Recent innovation on in situ TEM holders based on silicon micro chips have led to great improvements compared to previous technologies. Still, in situ is a particularly complicated technique and experiments are extremely difficult to implement. This work provides new solutions to perform live observations at the atomic scale during both heating and biasing of a specimen inside the TEM. This was made possible through several improvements performed at different stages of the in situ TEM experiments. The main focus of this PhD concerned the issues faced during in situ biasing of a nanometer size resistive memory device. This was made possible through hardware investigation, sample preparation method developments, and in situ biasing TEM experiments.First, a new sample preparation method has been developed specifically to perform in situ heating experiments. Through this work, live crystallization of a GeTe phase change Memory Material is observed in the TEM. This allowed to obtain valuable information for the development of chalcogenide based Phase Change Resistive Memories. Then, new chips dedicated to in situ biasing experiments have been developed and manufactured. The FIB sample preparation is studied in order to improve electrical operation in the TEM. Quantitative TEM measurements are then performed on a reference PN junction to demonstrate the capabilities of this new in situ biasing experimental setup. By implementing these improvements performed on the TEM in situ biasing technique, results are obtained during live operation of a Conductive Bridge Resistive Memory device. This allowed to present new information on the resistive memories functioning mechanisms, as well as the in situ TEM characterization technique itself

This research studies a Transcutaneous Energy Transfer (TET) system which uses electromagnetic fields to transfer power from outside the body to an artificial organ (AO) in the body. It works like a high frequency transformer whereas the skin is part of the magnetic coupling between the primary (external) and secondary (internal) coils. Thus, the external coil (transmitter), which is excited by an oscillator circuit that transforms the continuous (DC) voltage to high-frequency alternating (AC) voltage, transfers energy to an internal system (receiver) containing a coil associated with a rectifier-regulator circuit to supply power to the AO and an internal rechargeable battery. Due to the diversity of research areas in TET systems, this thesis focused mainly on the TET coils, exploring few aspects of the electronic circuits which directly affect the proper design of the coils. Simulations of different configurations of coils (with different magnetic material types and different core geometrical dimensions) and different electrical parameters were performed via Finite Element Method (FEM) applications. Analyses of the results of these simulations with and without serial resonant capacitors (SRCs) observed the behavior of the coils considering the efficiency, regulation, specific absorption rate (SAR) and current density induced in the skin. These results also facilitated an optimization procedure using Kriging method without the need for new simulations via FEM. In parallel with the optimization procedure, different physical prototypes were created and tested to validate the simulations and explore the behavior of the coils. The temperature increase of the coils and the threshold limits of the electronic circuits were observed, suggesting new optimization strategies. Since the computation of the temperature is too complicated, the temperature rise was indirectly considered in this research by the use of a factor called thermo factor, which represents the relationship between the dissipated power and the area of the coil. Moreover, since the AO requires a constant power, the load of the TET system was modeled as a variable resistance. This thesis proposed an algorithm to compute this value of the variable resistance directly in the FEM simulations. Thus, another optimization procedure was proposed with the new mentioned strategy by directly interacting with the FEM application. In this second case, homogenization methods were used to simplify the mesh without neglecting eddy current, proximity and skin effects, thus allowing accurate simulations of coils with thicker wire gauges and at higher frequencies. In the end, the results of both simulations were briefly discussed to evaluate configurations eligible for construction or assembly.
Esse trabalho estuda um sistema de transferência de energia transcutâneo (TET) que, tal qual um transformador de alta freqüência, usa campos eletromagnéticos para transferir potência de fora do corpo a um órgão artificial dentro do corpo. Assim, a pele passa a ser parte do acoplamento magnético entre o primário (bobina externa) e o secundário (bobina interna). Dessa forma, a bobina externa (transmissor) é excitada por um circuito oscilador, gerando corrente alternada de alta freqüência e transfere energia ao sistema secundário interno (receptor) que contém uma bobina associada a um circuito retificador seguido de amplificadores e reguladores para alimentar o órgão artificial e/ou uma bateria recarregável interna. Devido à diversidade de áreas para pesquisar, esta tese teve as bobinas de TET como objetivo principal, explorando alguns aspectos dos circuitos eletrônicos que afetam diretamente o projeto adequado das bobinas. Simulações de diferentes configurações de bobinas (com diferentes tipos de material magnético e diferentes dimensões geométricas dos núcleos) e diferentes parâmetros elétricos foram realizados através de softwares de Método dos Elementos Finitos (FEM). Essas análises com e sem capacitores de ressonância série (SRCs) observaram o comportamento das bobinas considerando o rendimento, a regulação, a taxa de absorção específica (SAR) e densidade de corrente induzida na pele. Os resultados dessas simulações também facilitou um procedimento de otimização usando o método de Kriging, sem a necessidade de novas simulações via FEM. Em paralelo com o processo de optimização, diferentes protótipos físicos foram criados e testados para validar as simulações e explorar o comportamento das bobinas. O aumento da temperatura nas bobinas e os limites dos circuitos eletrônicos foram observados, sugerindo novas estratégias de otimização. Uma vez que o cálculo da temperatura é demasiado complicado, esta pesquisa sugere o uso de um fator, aqui denominado \"fator térmico\", para indiretamente considerar esse aumento de temperatura. Além disso, uma vez que o AO requer uma potência constante, a carga do transformador de TET foi modelada como uma resistência variável. Esta tese propõe um algoritmo para calcular este valor de resistência variável diretamente nas simulações com FEM. Assim, foi proposto um outro procedimento de otimização com a nova estratégia mencionada, interagindo diretamente com a aplicação de FEM. Neste segundo caso, os métodos de homogeneização foram utilizados para simplificar a malha sem ignorar correntes de Foucault, e os efeitos pelicular e de proximidade, permitindo simulações precisas de bobinas com fios mais grossos e em frequências mais altas. Os resultados de ambas as simulações foram discutidos brevemente no final para avaliar configurações elegíveis para serem montadas.

Increasing the level of semiconductor devices' quality, reliability, and associated system safety is important as a fundamental contributor to overall technical advancement in the electronics sector. However, the growing requirements of optimizing device design for the broadest application areas need an enhanced level of understanding of thermal behaviour, and self-heating in particular, of semiconductor devices under harsh thermal operation conditions. The aim of the research presented in this thesis is to develop and verify a numerical tool to assist in the understanding and the prediction of phenomena that contribute to the ageing and stressing of semiconductor devices. An aged semiconductor device can substantially adversely affect a system's electromagnetic compatibility (EMC) performance and reduce the desired functionality. The chosen method is a co-simulation approach for a linked electrical and thermal model, using the Transmission Line Matrix (TLM) method. This selection is based on having a single method that can simulate both domains, that is intuitive and flexible. The method is enhanced by including electromigration and thermomigration mechanisms as an influential element in the calculation of material properties inside the hybrid solver. The proposed model was subjected to a customized Thermal Cycling Test (TCT) in order to observe device behaviour and comprehend the degradation phenomenon that Abstract appears after accelerated ageing test in RF LDMOS device. The research is a generic step forward, showing that a single TLM 'engine' can be used to model the linked factors in ageing and its effects, namely electrical, and thermal behaviour, that also allows for probabilistic events such as electro/thermo-migration. Further, the method developed in this thesis is applied to two problem areas: • Silicon nanowires, where the thermal radiation effects are addressed by adding an additional shunt conductance to a one-dimensional TLM node structure. The results demonstrate good agreement with previously published results and provide an appropriate tool to solve the internal heating problems and, hence, the degradation caused by thermal factors for future semiconductor devices. • Silicon Carbide Metal-Semiconductor Field Effect Transistor (MESFET) and RF Laterally Diffused Metal Oxide Semiconductor (LDMOS) devices, which are approached as 2D structures, where the probability of occurring electromigration and thermomigration phenomenon in MESFET devices is investigated and the MTTF is shown when the model is subjected to thermal stress. The TCT is applied as a thermal acceleration factor in a MOS device, where the impact on the device IV (current-voltage) characteristic is studied. The results demonstrated good agreement with previous published results.

The current study compared the performance of six commonly used cursor devices (absolute touchpad, mouse, trackball, relative touchpad, force joystick, and displacement joystick) on three types of tasks (target acquisition, text editing, and graphics). Prior to these comparisons, each of the devices was optimized for display/control dynamics in independent experiments. A total of 30 subjects were used in the five optimization studies. For each device, the optimization experiment compared a range of control dynamics using a target acquisition task (i.e., positioning a cross-hair cursor over square targets of varying sizes and screen distances). An analysis of variance procedure was used to determine the best control dynamics, of the range studied, for each device. Performance was based on a time-to-target (TT) measure. A comparison of the six optimized devices was then performed on the three task environments. For the target acquisition, text editing, and graphics tasks, a total of 12, seven, and six subjects were required, respectively. For the target acquisition study, the six devices were compared on a task identical to the optimization task; that is, cursor positioning performance for various target sizes and distances. In addition to the TT dependent measure, bipolar scale and subjective rank data were also collected. The text editing task required subjects to perform document correction on the computer using each of the six devices, with cursor keys added as a baseline device. Task completion time (TCT), bipolar scale response, and subjective rank data were collected. For the graphics task, subjects were required to perform basic graphics editing tasks with the six devices. As with the text editing task, TCT, bipolar scale, and rank data were collected. Results indicated a wide variation in the cursor positioning performance of the devices on the three tasks. Without exception, the mouse and trackball performed the best of the six devices, across all tasks. In addition, these devices were most preferred. In general, the two joysticks performed worse on the target acquisition and graphics tasks than the two touchpads. On the text editing task, however, the rate—controlled joysticks performed better than the touchpads.
Ph. D.

Thesis (PhD)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: Accurate load models are required for the computation of load flows in MV distribution networks. Modem microprocessors in recent times enable researchers to sample and log domestic loads. The findings show that they are stochastic in nature and are best described by a beta probability distribution. . In rural areas two different load types may be present. Such loads are domestic and pump loads, the latter may be modelled as constant P - Q loads. An analytical tool for computing voltage regulation on MV distribution networks for rural areas feeding the mentioned loads is therefore required. The statistical evaluation of the consumer voltages requires a description of load currents at the time of the system maximum demand. To obtain overall consumer voltages at any specified risk for the two types of the loads, the principle of superposition is adopted. The present work deals with conventional 22kV three-phase distribution (te:. - te:.) connected networks as used by ESKOM, South Africa. As the result of the connected load, MV networks can experience poor voltage regulation. To solve the problem of voltage regulation, voltage regulators are employed. The voltage regulators considered are step-voltage regulators, capacitors and USE (Universal Semiconductor Electrification) devices. USE devices can compensate for the voltage drops of up to 35% along the MV distribution network, thus the criteria for the application of the USE devices is also investigated. The load currents are treated as signals when assessing the cost of distribution system over a period of time due to power losses. The individual load current signal is modelled by its mean and standard deviation. The analytical work for developing general expressions of the total real and total imaginary components of branch voltage drops and line power losses in single and three-phase networks without branches are presented. To deal with beta-distributed currents on MV distribution networks, new scaling factors are evaluated at each node. These new scaling factors are derived from the distribution transformer turns ratio and the deterministic component of the statistically distributed load currents treated as constant real power loads. In the case of an individual load current signal, the transformation ratio is evaluated from the distribution transformer turns ratio and the average value of the· signal treated as constant real power load. The evaluation of the consumer voltage percentile values can be accurately evaluated up to 35% voltage drop. This is possible by the application of the expanded Taylor series, using the first three terms. The coefficients of these three terms were obtained using a search engine imbedded in the probabilistic load flow. The general expressions for evaluating the overall consumer voltages due to statistical and non-statistical loads currents are also given. These non-statistical currents may be due to constant P - Q loads, line capacitance and the modeling of voltage regulators. The Newton-Raphson algorithm is applied to perform a deterministic load flow on singlephase networks. A backward and forward sweep algorithm is applied to perform a deterministic load flow on single and three-phase systems. A new procedure for modelling step-voltage regulators in three-phase (te:. - te:.) connected networks is outlined. Specifying a transformation ratio of 1.1 and 1.15 respectively, identifies the open-delta or closed-delta configuration for three-phase networks. The algorithms and the developed general expressions for single and three-phase networks without branches are presented in this work. A new algorithm is developed to enable the developed general expressions to be applied to practical MV distribution networks. The algorithms were tested for their accuracy by comparing the analytical results with Monte Carlo simulation and they compared well. An illustrative example to show the application of the present work on a practical MY distribution networks is presented. A criterion for the application of the USE devices is outlined. It is anticipated that, the work presented in this thesis will be invaluable to those involved in the design of MY distribution systems in developing countries.
AFRIKAANSE OPSOMMING: Akkurate lasrnodelle word benodig vir drywingsvloei analises in MV distribusiestelsels. As gevolg van nuwe digitale verwerkers is dit deesdae moontlik om huishoudelike laste te monitor. Die lasdata dui daarop dat laste stochasties is en kan met behulp van die Beta verdeling beskryf word. In landelike gebiede is daar twee tipes laste. Hulle is eendersyds huishoudelike laste en andersyds pomp-tipe laste wat as konstante P-Q laste beskou kan word. Dit is dus belangrik om toepaslike analitiese metodes te gebruik om die spanningsvalle by hierdie laste te bereken met inagname van die las-tipes. By die statistiese berekening van die verbruiker se spanning moet 'n statistiese model van die lasstroom verskaf word op die tydstip van maksimum aanvraag. Daarna moet die prinsiep van superposissie gebruik word om die spannings by verskeie nodes by 'n gespesifiseerde vertrouensinterval te bepaal. Hierdie proefskrif is gebaseer op konvensionele 22kV, drie fase distribusie (delta na delta) netwerke, soos deur Eskom, Suid Afrika gebruik. Hierdie stelsels ondervind dikwels nadelige spanningsvlakke en spanningsreëlaars word derhalwe aangewend. Hierdie reëlaars is gewoonlik van tap-tipe of daar kan ook gebruik gemaak word van kapasitore en ook elektroniese reëlaars soos die USE tipe toestelle. Laasgenoemde kan op LV vir spanningsvalle tot 35% kompenseer. In hierdie werk word die werkdrywing verliese in die geleiers bereken met behulp 'n seinmodel van die lasstrome. Die individuele lasstrome word by wyse van gemiddeldes en variasies beskryf. Om die algemene algoritmes vir die berekening van die reële en imaginêre spanningsvalle, asook die verliese in enkelfase en driefase stelsels daar te stel word aanvanklik gebruik gemaak van stelsels sonder vertakkings. Om die statistiese lasbeskrywing op die laagspanningskant na die MV vlak oor te dra word van nuwe skaalfaktore gebruik gemaak. Hierdie faktore word bereken op die basis van die transformator se verhouding en die deterministiese komponent van die statistiese verspreide lasstrome, as konstante reële drywingslaste beskou. Met die ontwikkelde metode kan die verbruiker se spanning by 'n gegewe vertrouensinterval akkuraat bereken word vir spanningsvalle tot 35%. Dit word moontlik gemaak deur die Taylor-reeks tot drie terme toe te pas. Daar moet egter gebruik gemaak word van toepaslike koëffisiënte wat bepaal word deur 'n geprogrammeerde soektog. 'n Algemene stel vergelykings om die spanning by enige verbruiker te bereken, ongeag die topologie van die netwerk, word ook gegee. Die Newton-Raphson metode word aangewend om die deterministiese drywingsvloei op enkelfase stelsels te bereken. A truwaartse-voorwaartse metode is gebruik om die drywingsvloei te bepaal vir driefase stelsels. 'n Nuwe prosedure is ontwikkel vir die modellering van die spanningsreëlaars in driefase, delta-delta netwerke. Deur gebruik te maak van 'n transformatorverhouding van 1.1 of 1.15 kan die oop-delta of toe-delta netwerke voorgestel word. 'n Nuwe algoritme is ontwikkelom multi-vertakkings in 'n netwerk te hanteer. Al die prosedures is deeglik met behulp van Monte Carlo simulasies getoets en die resultate is heel bevredigend. Om die metodes te illustreer word 'n gevallestudie ingesluit waar die metodes gebruik word om 'n netwerk te evalueer met en sonder die sogenaamde USE toestelle. Kriteria vir die aanwending van hierdie toerusting word voorgestel. Daar word verwag dat die werk soos in hierdie proefskrifuiteengesit is die ontwerp van MV distribusiestelsels, veral in ontwikkelende lande, heelwat sal verbeter.

For studying the response to transients caused by lightning and other electromagnetic disturbance sources, electrified railway systems can be represented as a system of multiconductor transmission lines (MTL) above a finitely conducting ground. The conductors present in this system would be wires for traction power supply, auxiliary power, return conductors for traction current, the tracks, and finitely conducting ground. In contrast to conventional power systems, where the MTL system is usually only terminated at the line ends, there are lumped devices connected in series and as shunt along the railway network, for example, booster and auto transformers, track circuits, and various interconnections between conductors, influencing surge propagation. In this doctorial thesis a new method for incorporating lumped series and shunt connected devices along MTL systems is presented. Telegrapher’s equations, using the finite difference time domain method, are adopted for finding surge pulse propagations along the MTL systems, simultaneously solving for the lumped devices connected along the lines by means of Kirchoff’s laws for nodal currents and voltages using a circuit solver. As part of this work, case studies are carried out to determine voltages appearing across devices connected along MTL systems representative of a typical Swedish single-track electrified railway system, in cases of direct and indirect lightning strikes. The influence of soil ionization at the grounding points and the nonlinear phenomenon of flashovers between overhead wires and the poles are also investigated. The calculations made show that the devices connected along this system, which are needed for normal and safe operation of the railway system, and nonlinearities are affecting the surge current and voltage distribution and peaks appearing along the MTL system and across devices.

The tractive force has to be interrupted during a gear-shifting operation in a manual vehicle transmission, leading into a decrease of speed while changing gears during the acceleration process. Therefore in a racing application, the shifting time has to be as short as possible so that the required performance of a racing car can be achieved. The following dissertation describes the development of a transmission control system to enable gear changes within a manual gearbox, which was designed for the Formula Student racing series. Various solutions were developed on the basis of reviewed literature, technical data of components and experiences of Formula Student teams. Following this, a comparison of the concepts by means of a utility analysis identified the pneumatic actuation of selector forks to be the most suitable concept. This was mainly due to the expected shifting time, the weight, and its advantageous energy supply requirement. After the selection of the actuators and the position sensors, the system was implemented into the drivetrain to check the tment and the technical feasibility. To draw conclusions regarding the shifting time and to prove the functionality of the system, an open test bench was constructed. Additionally, the hardware and software had to be developed to enable the test run. After the manufacturing and assembling of the test bench, the optimal settings for the test run were determined. By comparing the achieved shifting time of alternative solutions, an improvement in the driving performance of a Formula Student race car is probable.

The purpose of this thesis is the construction of a test bench for the assessment of the NVH behaviour of a newly manufactured VW Polo 5. This will be done in collaboration with Volkswagen South Africa. Firstly, in order to gain a better understanding of the requirements such a test bench has to fulfill, the VW Polo, the guidelines prescribed by VW as well as the actual testing procedure implemented by VW Uitenhage will be analysed. Thereafter, the main section of the thesis will deal with the construction of the test bench. As agreed upon with Volkswagen Uitenhage, a test bench will be built during the course of the studies. This test bench will allow stimulation in low frequency as well as high frequency ranges and in addition to that, a second version of the test bench with optimised costing will be derived from the first one. The second model will only allow stimulation in high frequency ranges. During the thesis, a version of the test bench, the RTB-HC, has been developed which enables the stimulation of the high and low frequencies. In addition, a cost optimized version was developed. This version will be referred as RTB-LC. This version allows only a high frequency excitation.

This thesis is devoted to the development of new models for a recently-implemented FACTS (flexible alternating current transmission system) device, the unified power flow controller (UPFC), and the control coordination of power systems with FACTS devices in steady-state operating mode. The key objectives of the research reported in the thesis are, through online control coordination based on the models of power systems having FACTS devices, those of maximising the network operational benefit and restoring system static security following a disturbance or contingency. Based on the novel concept of interpreting the updated voltage solutions at each iteration in the Newton-Raphson (NR) power-flow analysis as dynamic variables, the thesis first develops a procedure for representing the unified power flow controllers (UPFCs) in the steady-state evaluation. Both the shunt converter and series converter control systems of a UPFC are modeled in their dynamical form with the discrete time variable replaced by the NR iterative step in the power-flow analysis. The key advantage of the model developed is that of facilitating the process of UPFC constraint resolution during the NR solution sequence. Any relative priority in control functions pre-set in the UPFC controllers is automatically represented in the power-flow formulation. Although the developed UPFC model based on the dynamic simulation of series and shunt converter controllers is flexible and general, the number of NR iterations required for convergence can be large. Therefore, the model is suitable mainly for power system planning and design studies. For online control coordination, the thesis develops the second UPFC model based on nodal voltages. The model retains all of the flexibility and generality of the dynamic simulation-based approach while the number of iterations required for solution convergence is independent of the UPFC controller dynamic responses. Drawing on the constrained optimisation based on Newton’s method together with the new UPFC model expressed in terms of nodal voltages, a systematic and general method for determining optimal reference inputs to UPFCs in steady-state operation is developed. The method is directly applicable to UPFCs operation with a high-level line optimisation control (LOC) for maximising the network operational benefit. By using a new continuation technique with adaptive parameter, the algorithm for solving the constrained optimisation problem extends substantially the region of convergence achieved with the conventional Newton’s method. Having established the foundation provided by the comprehensive models developed for representing power systems with FACTS devices including the UPFC, the research, in the second part, focuses on real-time control coordination of power system controllers, with the main purpose of restoring power system static security following a disturbance or contingency. At present, as the cost of phasor measurement units (PMUs) and wide-area communication network is on the decrease, the research proposes and develops a new secondary voltage control where voltages at all of the load nodes are directly controlled, using measured voltages.

This thesis employs computational and experimental methods to explore hotspot cooling and high heat flux removal from a 3-D stacked chip using thermoelectric and microfluidic devices. Stacked chips are expected to improve microelectronics performance, but present severe thermal management challenges. The thesis provides an assessment of both thermoelectric and microfluidic technologies and provides guidance for their implementation in the 3-D stacked chips. A detailed 3-D thermal model of a stacked electronic package with two dies and four ultrathin integrated TECs is developed to investigate the efficacy of TECs in hotspot cooling for 3-D technology. The numerical analysis suggests that TECs can be used for on demand cooling of hotspots in 3-D stacked chip architecture. A strong vertical coupling is observed between the top and bottom TECs and it is found that the bottom TECs can detrimentally heat the top hotspots. As a result, TECs need to be carefully placed inside the package to avoid such undesired heating. Thermal contact resistances between dies, inside the TEC module, and between the TEC and heat spreader are shown to significantly affect TEC performance. TECs are most effective for cooling localized hotspots, but microchannels are advantageous for cooling large background heat fluxes. In the present work, the results of heat transfer and pressure drop experiments in the microchannels with water as the working fluid are presented and compared to the previous microchannel experiments and CFD simulations. Heat removal rates of greater than 100 W/cm2 are demonstrated with these microchannels, with a pressure drop of 75 kPa or less. A novel empirical correlation modeling method is proposed, which uses finite element modeling to model conduction in the channel walls and substrate, coupled with an empirical correlation to determine the convection coefficient. This empirical correlation modeling method is compared to resistor network and CFD modeling. The proposed modeling method produced more accurate results than resistor network modeling, while solving 60% faster than a conjugate heat transfer model using CFD. The results of this work demonstrate that microchannels have the ability to remove high heat fluxes from microelectronic packages using water as a working fluid. Additionally, TECs can locally cool hotspots, but must be carefully placed to avoid undesired heating. Future work should focus on overcoming practical challenges including fabrication, cost, and reliability which are preventing these technologies from being fully leveraged.

This study has been conducted to develop robust event detection and object tracking algorithms that can be implemented in real time video surveillance applications. The aim of the research has been to produce an automated video surveillance system that is able to detect and report potential security risks with minimum human intervention. Since the algorithms are designed to be implemented in real-life scenarios, they must be able to cope with strong illumination changes and occlusions. The thesis is divided into two major sections. The first section deals with event detection and edge based tracking while the second section describes colour measurement methods developed to track objects in crowded environments. The event detection methods presented in the thesis mainly focus on detection and tracking of objects that become stationary in the scene. Objects such as baggage left in public places or vehicles parked illegally can cause a serious security threat. A new pixel based classification technique has been developed to detect objects of this type in cluttered scenes. Once detected, edge based object descriptors are obtained and stored as templates for tracking purposes. The consistency of these descriptors is examined using an adaptive edge orientation based technique. Objects are tracked and alarm events are generated if the objects are found to be stationary in the scene after a certain period of time. To evaluate the full capabilities of the pixel based classification and adaptive edge orientation based tracking methods, the model is tested using several hours of real-life video surveillance scenarios recorded at different locations and time of day from our own and publically available databases (i-LIDS, PETS, MIT, ViSOR). The performance results demonstrate that the combination of pixel based classification and adaptive edge orientation based tracking gave over 95% success rate. The results obtained also yield better detection and tracking results when compared with the other available state of the art methods. In the second part of the thesis, colour based techniques are used to track objects in crowded video sequences in circumstances of severe occlusion. A novel Adaptive Sample Count Particle Filter (ASCPF) technique is presented that improves the performance of the standard Sample Importance Resampling Particle Filter by up to 80% in terms of computational cost. An appropriate particle range is obtained for each object and the concept of adaptive samples is introduced to keep the computational cost down. The objective is to keep the number of particles to a minimum and only to increase them up to the maximum, as and when required. Variable standard deviation values for state vector elements have been exploited to cope with heavy occlusion. The technique has been tested on different video surveillance scenarios with variable object motion, strong occlusion and change in object scale. Experimental results show that the proposed method not only tracks the object with comparable accuracy to existing particle filter techniques but is up to five times faster. Tracking objects in a multi camera environment is discussed in the final part of the thesis. The ASCPF technique is deployed within a multi-camera environment to track objects across different camera views. Such environments can pose difficult challenges such as changes in object scale and colour features as the objects move from one camera view to another. Variable standard deviation values of the ASCPF have been utilized in order to cope with sudden colour and scale changes. As the object moves from one scene to another, the number of particles, together with the spread value, is increased to a maximum to reduce any effects of scale and colour change. Promising results are obtained when the ASCPF technique is tested on live feeds from four different camera views. It was found that not only did the ASCPF method result in the successful tracking of the moving object across different views but also maintained the real time frame rate due to its reduced computational cost thus indicating that the method is a potential practical solution for multi camera tracking applications.

Actuellement, il existe une forte demande de Headstage et de microsystèmes intégrés implantables pour étudier l’activité cérébrale de souris de laboratoire en mouvement libre. De tels dispositifs peuvent s’interfacer avec le système nerveux central dans les paradigmes électriques et optiques pour stimuler et surveiller les circuits neuronaux, ce qui est essentiel pour découvrir de nouveaux médicaments et thérapies contre des troubles neurologiques comme l’épilepsie, la dépression et la maladie de Parkinson. Puisque les systèmes implantables ne peuvent pas utiliser une batterie ayant une grande capacité en tant que source d’énergie primaire dans des expériences à long terme, la consommation d’énergie du dispositif implantable est l’un des principaux défis de ces conceptions. La première partie de cette recherche comprend notre proposition de la solution pour diminuer la consommation d’énergie des microcircuits implantables. Nous proposons un nouveau circuit de décalage de niveau qui convertit les niveaux de signaux sub-seuils en niveaux ultra-bas à haute vitesse en utilisant une très faible puissance et une petite zone de silicium, ce qui le rend idéal pour les applications de faible puissance. Le circuit proposé introduit une nouvelle topologie de décaleur de niveau de tension utilisant un condensateur de décalage de niveau pour augmenter la plage de tensions de conversion, tout en réduisant considérablement le retard de conversion. Le circuit proposé atteint un délai de propagation plus court et une zone de silicium plus petite pour une fréquence de fonctionnement et une consommation d’énergie donnée par rapport à d’autres solutions de circuit. Les résultats de mesure sont présentés pour le circuit proposé fabriqué dans un processus CMOS TSMC de 0,18- mm. Le circuit présenté peut convertir une large gamme de tensions d’entrée de 330 mV à 1,8 V et fonctionner sur une plage de fréquence de 100 Hz à 100 MHz. Il a un délai de propagation de 29 ns et une consommation d’énergie de 61,5 nW pour les signaux d’entrée de 0,4 V, à une fréquence de 500 kHz, surpassant les conceptions précédentes. La deuxième partie de cette recherche comprend nos systèmes de transfert d’énergie sans fil proposé pour les applications optogénétiques. L’optogénétique est la combinaison de la méthode génétique et optique d’excitation, d’enregistrement et de contrôle des neurones biologiques. Ce système combine plusieurs technologies telles que les MEMS et la microélectronique pour collecter et transmettre les signaux neuronaux et activer un stimulateur optique via une liaison sans fil. Puisque les stimulateurs optiques consomment plus de puissance que les stimulateurs électriques, l’interface utilise la transmission de puissance par induction en utilisant des moyens innovants au lieu de la batterie avec la petite capacité comme source d’énergie.
Actuellement, il existe une forte demande de Headstage et de microsystèmes intégrés implantables pour étudier l’activité cérébrale de souris de laboratoire en mouvement libre. De tels dispositifs peuvent s’interfacer avec le système nerveux central dans les paradigmes électriques et optiques pour stimuler et surveiller les circuits neuronaux, ce qui est essentiel pour découvrir de nouveaux médicaments et thérapies contre des troubles neurologiques comme l’épilepsie, la dépression et la maladie de Parkinson. Puisque les systèmes implantables ne peuvent pas utiliser une batterie ayant une grande capacité en tant que source d’énergie primaire dans des expériences à long terme, la consommation d’énergie du dispositif implantable est l’un des principaux défis de ces conceptions. La première partie de cette recherche comprend notre proposition de la solution pour diminuer la consommation d’énergie des microcircuits implantables. Nous proposons un nouveau circuit de décalage de niveau qui convertit les niveaux de signaux sub-seuils en niveaux ultra-bas à haute vitesse en utilisant une très faible puissance et une petite zone de silicium, ce qui le rend idéal pour les applications de faible puissance. Le circuit proposé introduit une nouvelle topologie de décaleur de niveau de tension utilisant un condensateur de décalage de niveau pour augmenter la plage de tensions de conversion, tout en réduisant considérablement le retard de conversion. Le circuit proposé atteint un délai de propagation plus court et une zone de silicium plus petite pour une fréquence de fonctionnement et une consommation d’énergie donnée par rapport à d’autres solutions de circuit. Les résultats de mesure sont présentés pour le circuit proposé fabriqué dans un processus CMOS TSMC de 0,18- mm. Le circuit présenté peut convertir une large gamme de tensions d’entrée de 330 mV à 1,8 V et fonctionner sur une plage de fréquence de 100 Hz à 100 MHz. Il a un délai de propagation de 29 ns et une consommation d’énergie de 61,5 nW pour les signaux d’entrée de 0,4 V, à une fréquence de 500 kHz, surpassant les conceptions précédentes. La deuxième partie de cette recherche comprend nos systèmes de transfert d’énergie sans fil proposé pour les applications optogénétiques. L’optogénétique est la combinaison de la méthode génétique et optique d’excitation, d’enregistrement et de contrôle des neurones biologiques. Ce système combine plusieurs technologies telles que les MEMS et la microélectronique pour collecter et transmettre les signaux neuronaux et activer un stimulateur optique via une liaison sans fil. Puisque les stimulateurs optiques consomment plus de puissance que les stimulateurs électriques, l’interface utilise la transmission de puissance par induction en utilisant des moyens innovants au lieu de la batterie avec la petite capacité comme source d’énergie.
Notre première contribution dans la deuxième partie fournit un système de cage domestique intelligent basé sur des barrettes multi-bobines superposées à travers un récepteur multicellulaire implantable mince de taille 1×1 cm2, implanté sous le cuir chevelu d’une souris de laboratoire, et unité de gestion de l’alimentation intégrée. Ce système inductif est conçu pour fournir jusqu’à 35,5 mW de puissance délivrée à un émetteur-récepteur full duplex de faible puissance entièrement intégré pour prendre en charge des implants neuronaux à haute densité et bidirectionnels. L’émetteur (TX) utilise une bande ultra-large à impulsions radio basée sur des approches de combinaison, et le récepteur (RX) utilise une topologie à bande étroite à incrémentation de 2,4 GHz. L’émetteur-récepteur proposé fournit un débit de données de liaison montante TX à 500 Mbits/s double et un débit de données de liaison descendante RX à 100 Mbits/s, et est entièrement intégré dans un processus CMOS TSMC de 0,18-mm d’une taille totale de 0,8 mm2 . La puissance peut être délivrée à partir d’un signal de porteuse de 13,56-MHz avec une efficacité globale de transfert de puissance supérieure à 5% sur une distance de séparation allant de 3 cm à 5 cm. Notre deuxième contribution dans les systèmes de collecte d’énergie porte sur la conception et la mise en oeuvre d’une cage domestique de transmission de puissance sans fil (WPT) pour une plate-forme de neurosciences entièrement sans fil afin de permettre des expériences optogénétiques ininterrompues avec des rongeurs de laboratoire vivants. La cage domestique WPT utilise un nouveau réseau hybride de transmetteurs de puissance (TX) et des résonateurs multi-bobines segmentés pour atteindre une efficacité de transmission de puissance élevée (PTE) et délivrer une puissance élevée sur des distances aussi élevées que 20 cm. Le récepteur de puissance à bobines multiples (RX) utilise une bobine RX d’un diamètre de 1 cm et une bobine de résonateur d’un diamètre de 1,5 cm. L’efficacité moyenne du transfert de puissance WPT est de 29, 4%, à une distance nominale de 7 cm, pour une fréquence porteuse de 13,56 MHz. Il a des PTE maximum et minimum de 50% et 12% le long de l’axe Z et peut délivrer une puissance constante de 74 mW pour alimenter le headstage neuronal miniature. En outre, un dispositif implantable intégré dans un processus CMOS TSMC de 0,18-mm a été conçu et introduit qui comprend 64 canaux d’enregistrement, 16 canaux de stimulation optique, capteur de température, émetteur-récepteur et unité de gestion de l’alimentation (PMU). Ce circuit est alimenté à l’intérieur de la cage du WPT à l’aide d’une bobine réceptrice d’un diamètre de 1,5 cm pour montrer les performances du circuit PMU. Deux tensions régulées de 1,8 V et 1 V fournissent 79 mW de puissance pour tout le système sur une puce. Notre dernière contribution est un système WPT insensible aux désalignements angulaires pour alimenter un headstage pour des applications optogénétiques qui a été précédemment proposé par le Laboratoire de Microsystèmes Biomédicaux (BioML-UL) à ULAVAL. Ce système est la version étendue de notre deuxième contribution aux systèmes de collecte d’énergie.Dans la version mise à jour, un récepteur de puissance multi-bobines utilise une bobine RX d’un diamètre de 1,0 cm et une nouvelle bobine de résonateur fendu d’un diamètre de 1,5 cm, qui résiste aux défauts d’alignement angulaires. Dans cette version qui utilise une cage d’animal plus petite que la dernière version, 4 résonateurs sont utilisés côté TX. De plus, grâce à la forme et à la position de la bobine de répéteur L3 du côté du récepteur, la liaison résonnante hybride présentée peut correctement alimenter la tête sans interruption causée par le désalignement angulaire dans toute la cage de la maison. Chaque 3 tours du répéteur RX a été enveloppé avec un diamètre de 1,5 cm, sous différents angles par rapport à la bobine réceptrice. Les résultats de mesure montrent un PTE maximum et minimum de 53 % et 15 %. La méthode proposée peut fournir une puissance constante de 82 mW pour alimenter le petit headstage neural pour les applications optogénétiques. De plus, dans cette version, la performance du système est démontrée dans une expérience in-vivo avec une souris ChR2 en mouvement libre qui est la première expérience optogénétique sans fil et sans batterie rapportée avec enregistrement électrophysiologique simultané et stimulation optogénétique. L’activité électrophysiologique a été enregistrée après une stimulation optogénétique dans le Cortex Cingulaire Antérieur (CAC) de la souris.
Notre première contribution dans la deuxième partie fournit un système de cage domestique intelligent basé sur des barrettes multi-bobines superposées à travers un récepteur multicellulaire implantable mince de taille 1×1 cm2, implanté sous le cuir chevelu d’une souris de laboratoire, et unité de gestion de l’alimentation intégrée. Ce système inductif est conçu pour fournir jusqu’à 35,5 mW de puissance délivrée à un émetteur-récepteur full duplex de faible puissance entièrement intégré pour prendre en charge des implants neuronaux à haute densité et bidirectionnels. L’émetteur (TX) utilise une bande ultra-large à impulsions radio basée sur des approches de combinaison, et le récepteur (RX) utilise une topologie à bande étroite à incrémentation de 2,4 GHz. L’émetteur-récepteur proposé fournit un débit de données de liaison montante TX à 500 Mbits/s double et un débit de données de liaison descendante RX à 100 Mbits/s, et est entièrement intégré dans un processus CMOS TSMC de 0,18-mm d’une taille totale de 0,8 mm2 . La puissance peut être délivrée à partir d’un signal de porteuse de 13,56-MHz avec une efficacité globale de transfert de puissance supérieure à 5% sur une distance de séparation allant de 3 cm à 5 cm. Notre deuxième contribution dans les systèmes de collecte d’énergie porte sur la conception et la mise en oeuvre d’une cage domestique de transmission de puissance sans fil (WPT) pour une plate-forme de neurosciences entièrement sans fil afin de permettre des expériences optogénétiques ininterrompues avec des rongeurs de laboratoire vivants. La cage domestique WPT utilise un nouveau réseau hybride de transmetteurs de puissance (TX) et des résonateurs multi-bobines segmentés pour atteindre une efficacité de transmission de puissance élevée (PTE) et délivrer une puissance élevée sur des distances aussi élevées que 20 cm. Le récepteur de puissance à bobines multiples (RX) utilise une bobine RX d’un diamètre de 1 cm et une bobine de résonateur d’un diamètre de 1,5 cm. L’efficacité moyenne du transfert de puissance WPT est de 29, 4%, à une distance nominale de 7 cm, pour une fréquence porteuse de 13,56 MHz. Il a des PTE maximum et minimum de 50% et 12% le long de l’axe Z et peut délivrer une puissance constante de 74 mW pour alimenter le headstage neuronal miniature. En outre, un dispositif implantable intégré dans un processus CMOS TSMC de 0,18-mm a été conçu et introduit qui comprend 64 canaux d’enregistrement, 16 canaux de stimulation optique, capteur de température, émetteur-récepteur et unité de gestion de l’alimentation (PMU). Ce circuit est alimenté à l’intérieur de la cage du WPT à l’aide d’une bobine réceptrice d’un diamètre de 1,5 cm pour montrer les performances du circuit PMU. Deux tensions régulées de 1,8 V et 1 V fournissent 79 mW de puissance pour tout le système sur une puce. Notre dernière contribution est un système WPT insensible aux désalignements angulaires pour alimenter un headstage pour des applications optogénétiques qui a été précédemment proposé par le Laboratoire de Microsystèmes Biomédicaux (BioML-UL) à ULAVAL. Ce système est la version étendue de notre deuxième contribution aux systèmes de collecte d’énergie.Dans la version mise à jour, un récepteur de puissance multi-bobines utilise une bobine RX d’un diamètre de 1,0 cm et une nouvelle bobine de résonateur fendu d’un diamètre de 1,5 cm, qui résiste aux défauts d’alignement angulaires. Dans cette version qui utilise une cage d’animal plus petite que la dernière version, 4 résonateurs sont utilisés côté TX. De plus, grâce à la forme et à la position de la bobine de répéteur L3 du côté du récepteur, la liaison résonnante hybride présentée peut correctement alimenter la tête sans interruption causée par le désalignement angulaire dans toute la cage de la maison. Chaque 3 tours du répéteur RX a été enveloppé avec un diamètre de 1,5 cm, sous différents angles par rapport à la bobine réceptrice. Les résultats de mesure montrent un PTE maximum et minimum de 53 % et 15 %. La méthode proposée peut fournir une puissance constante de 82 mW pour alimenter le petit headstage neural pour les applications optogénétiques. De plus, dans cette version, la performance du système est démontrée dans une expérience in-vivo avec une souris ChR2 en mouvement libre qui est la première expérience optogénétique sans fil et sans batterie rapportée avec enregistrement électrophysiologique simultané et stimulation optogénétique. L’activité électrophysiologique a été enregistrée après une stimulation optogénétique dans le Cortex Cingulaire Antérieur (CAC) de la souris.
Our first contribution in the second part provides a smart home-cage system based on overlapped multi-coil arrays through a thin implantable multi-coil receiver of 1×1 cm2 of size, implantable bellow the scalp of a laboratory mouse, and integrated power management circuits. This inductive system is designed to deliver up to 35.5 mW of power delivered to a fully-integrated, low-power full-duplex transceiver to support high-density and bidirectional neural implants. The transmitter (TX) uses impulse radio ultra-wideband based on an edge combining approach, and the receiver (RX) uses a 2.4- GHz on-off keying narrow band topology. The proposed transceiver provides dual-band 500-Mbps TX uplink data rate and 100-Mbps RX downlink data rate, and it is fully integrated into 0.18-mm TSMC CMOS process within a total size of 0.8 mm2. The power can be delivered from a 13.56-MHz carrier signal with an overall power transfer efficiency above 5% across a separation distance ranging from 3 cm to 5 cm. Our second contribution in power-harvesting systems deals with designing and implementation of a WPT home-cage for a fully wireless neuroscience platform for enabling uninterrupted optogenetic experiments with live laboratory rodents. The WPT home-cage uses a new hybrid parallel power transmitter (TX) coil array and segmented multi-coil resonators to achieve high power transmission efficiency (PTE) and deliver high power across distances as high as 20 cm. The multi-coil power receiver (RX) uses an RX coil with a diameter of 1 cm and a resonator coil with a diameter of 1.5 cm. The WPT home-cage average power transfer efficiency is 29.4%, at a nominal distance of 7 cm, for a power carrier frequency of 13.56-MHz. It has maximum and minimum PTE of 50% and 12% along the Z axis and can deliver a constant power of 74 mW to supply the miniature neural headstage. Also, an implantable device integrated into a 0.18-mm TSMC CMOS process has been designed and introduced which includes 64 recording channels, 16 optical stimulation channels, temperature sensor, transceiver, and power management unit (PMU). This circuit powered up inside the WPT home-cage using receiver coil with a diameter of 1.5 cm to show the performance of the PMU circuit. Two regulated voltages of 1.8 V and 1 V provide 79 mW of power for all the system on a chip. Our last contribution is an angular misalignment insensitive WPT system to power up a headstage which has been previously proposed by the Biomedical Microsystems Laboratory (BioML-UL) at ULAVAL for optogenetic applications. This system is the extended version of our second contribution in power-harvesting systems. In the updated version a multi-coil power receiver uses an RX coil with a diameter of 1.0 cm and a new split resonator coil with a diameter of 1.5 cm, which is robust against angular misalignment. In this version which is using a smaller animal home-cage than the last version, 4 resonators are used on the TX side. Also, thanks to the shape and position of the repeater coil of L3 on the receiver side, the presented hybrid resonant link can properly power up the headstage without interruption caused by the angular misalignment all over the home-cage. Each 3 turns of the RX repeater has been wrapped up with a diameter of 1.5 cm, in different angles compared to the receiver coil. Measurement results show a maximum and minimum PTE of 53 % and 15 %. The proposed method can deliver a constant power of 82 mW to supply the small neural headstage for the optogenetic applications. Additionally, in this version, the performance of the system is demonstrated within an in-vivo experiment with a freely moving ChR2 mouse which is the first fully wireless and batteryless optogenetic experiment reported with simultaneous electrophysiological recording and optogenetic stimulation. Electrophysiological activity was recorded after delivering optogenetic stimulation in the Anterior Cingulate Cortex (ACC) of the mouse.
Our first contribution in the second part provides a smart home-cage system based on overlapped multi-coil arrays through a thin implantable multi-coil receiver of 1×1 cm2 of size, implantable bellow the scalp of a laboratory mouse, and integrated power management circuits. This inductive system is designed to deliver up to 35.5 mW of power delivered to a fully-integrated, low-power full-duplex transceiver to support high-density and bidirectional neural implants. The transmitter (TX) uses impulse radio ultra-wideband based on an edge combining approach, and the receiver (RX) uses a 2.4- GHz on-off keying narrow band topology. The proposed transceiver provides dual-band 500-Mbps TX uplink data rate and 100-Mbps RX downlink data rate, and it is fully integrated into 0.18-mm TSMC CMOS process within a total size of 0.8 mm2. The power can be delivered from a 13.56-MHz carrier signal with an overall power transfer efficiency above 5% across a separation distance ranging from 3 cm to 5 cm. Our second contribution in power-harvesting systems deals with designing and implementation of a WPT home-cage for a fully wireless neuroscience platform for enabling uninterrupted optogenetic experiments with live laboratory rodents. The WPT home-cage uses a new hybrid parallel power transmitter (TX) coil array and segmented multi-coil resonators to achieve high power transmission efficiency (PTE) and deliver high power across distances as high as 20 cm. The multi-coil power receiver (RX) uses an RX coil with a diameter of 1 cm and a resonator coil with a diameter of 1.5 cm. The WPT home-cage average power transfer efficiency is 29.4%, at a nominal distance of 7 cm, for a power carrier frequency of 13.56-MHz. It has maximum and minimum PTE of 50% and 12% along the Z axis and can deliver a constant power of 74 mW to supply the miniature neural headstage. Also, an implantable device integrated into a 0.18-mm TSMC CMOS process has been designed and introduced which includes 64 recording channels, 16 optical stimulation channels, temperature sensor, transceiver, and power management unit (PMU). This circuit powered up inside the WPT home-cage using receiver coil with a diameter of 1.5 cm to show the performance of the PMU circuit. Two regulated voltages of 1.8 V and 1 V provide 79 mW of power for all the system on a chip. Our last contribution is an angular misalignment insensitive WPT system to power up a headstage which has been previously proposed by the Biomedical Microsystems Laboratory (BioML-UL) at ULAVAL for optogenetic applications. This system is the extended version of our second contribution in power-harvesting systems. In the updated version a multi-coil power receiver uses an RX coil with a diameter of 1.0 cm and a new split resonator coil with a diameter of 1.5 cm, which is robust against angular misalignment. In this version which is using a smaller animal home-cage than the last version, 4 resonators are used on the TX side. Also, thanks to the shape and position of the repeater coil of L3 on the receiver side, the presented hybrid resonant link can properly power up the headstage without interruption caused by the angular misalignment all over the home-cage. Each 3 turns of the RX repeater has been wrapped up with a diameter of 1.5 cm, in different angles compared to the receiver coil. Measurement results show a maximum and minimum PTE of 53 % and 15 %. The proposed method can deliver a constant power of 82 mW to supply the small neural headstage for the optogenetic applications. Additionally, in this version, the performance of the system is demonstrated within an in-vivo experiment with a freely moving ChR2 mouse which is the first fully wireless and batteryless optogenetic experiment reported with simultaneous electrophysiological recording and optogenetic stimulation. Electrophysiological activity was recorded after delivering optogenetic stimulation in the Anterior Cingulate Cortex (ACC) of the mouse.
Currently, there is a high demand for Headstage and implantable integrated microsystems to study the brain activity of freely moving laboratory mice. Such devices can interface with the central nervous system in both electrical and optical paradigms for stimulating and monitoring neural circuits, which is critical to discover new drugs and therapies against neurological disorders like epilepsy, depression, and Parkinson’s disease. Since the implantable systems cannot use a battery with a large capacity as a primary source of energy in long-term experiments, the power consumption of the implantable device is one of the leading challenges of these designs. The first part of this research includes our proposed solution for decreasing the power consumption of the implantable microcircuits. We propose a novel level shifter circuit which converting subthreshold signal levels to super-threshold signal levels at high-speed using ultra low power and a small silicon area, making it well-suited for low-power applications such as wireless sensor networks and implantable medical devices. The proposed circuit introduces a new voltage level shifter topology employing a level-shifting capacitor to increase the range of conversion voltages, while significantly reducing the conversion delay. The proposed circuit achieves a shorter propagation delay and a smaller silicon area for a given operating frequency and power consumption compared to other circuit solutions. Measurement results are presented for the proposed circuit fabricated in a 0.18-mm TSMC CMOS process. The presented circuit can convert a wide range of the input voltages from 330 mV to 1.8 V, and operate over a frequency range of 100-Hz to 100-MHz. It has a propagation delay of 29 ns, and power consumption of 61.5 nW for input signals 0.4 V, at a frequency of 500-kHz, outperforming previous designs. The second part of this research includes our proposed wireless power transfer systems for optogenetic applications. Optogenetics is the combination of the genetic and optical method of excitation, recording, and control of the biological neurons. This system combines multiple technologies such as MEMS and microelectronics to collect and transmit the neuronal signals and to activate an optical stimulator through a wireless link. Since optical stimulators consume more power than electrical stimulators, the interface employs induction power transmission using innovative means instead of the battery with the small capacity as a power source.
Currently, there is a high demand for Headstage and implantable integrated microsystems to study the brain activity of freely moving laboratory mice. Such devices can interface with the central nervous system in both electrical and optical paradigms for stimulating and monitoring neural circuits, which is critical to discover new drugs and therapies against neurological disorders like epilepsy, depression, and Parkinson’s disease. Since the implantable systems cannot use a battery with a large capacity as a primary source of energy in long-term experiments, the power consumption of the implantable device is one of the leading challenges of these designs. The first part of this research includes our proposed solution for decreasing the power consumption of the implantable microcircuits. We propose a novel level shifter circuit which converting subthreshold signal levels to super-threshold signal levels at high-speed using ultra low power and a small silicon area, making it well-suited for low-power applications such as wireless sensor networks and implantable medical devices. The proposed circuit introduces a new voltage level shifter topology employing a level-shifting capacitor to increase the range of conversion voltages, while significantly reducing the conversion delay. The proposed circuit achieves a shorter propagation delay and a smaller silicon area for a given operating frequency and power consumption compared to other circuit solutions. Measurement results are presented for the proposed circuit fabricated in a 0.18-mm TSMC CMOS process. The presented circuit can convert a wide range of the input voltages from 330 mV to 1.8 V, and operate over a frequency range of 100-Hz to 100-MHz. It has a propagation delay of 29 ns, and power consumption of 61.5 nW for input signals 0.4 V, at a frequency of 500-kHz, outperforming previous designs. The second part of this research includes our proposed wireless power transfer systems for optogenetic applications. Optogenetics is the combination of the genetic and optical method of excitation, recording, and control of the biological neurons. This system combines multiple technologies such as MEMS and microelectronics to collect and transmit the neuronal signals and to activate an optical stimulator through a wireless link. Since optical stimulators consume more power than electrical stimulators, the interface employs induction power transmission using innovative means instead of the battery with the small capacity as a power source.

Orientador: José Maria Campos dos Santos
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica, Faculdade de Engenharia Eletrica e de Computação e Instituto de Química
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Resumo: Os requisitos de qualidade sonora estão sendo cada vez mais utilizados no mercado de caminhões médios e pesados. Assim, proprietários de veículos sentem-se incomodados pelo ruído de engrenamento. O estudo do ruído de engrenamento neste trabalho baseia-se em um par engrenado de um motor diesel pesado de aplicação veicular. Como primeiro estudo foi calculado o erro de transmissão das engrenagens por meio das deformações dos dentes sob carga que conforme a literatura a sua amplitude de pico a pico está diretamente relacionada com o ruído de engrenamento. A verificação desta influência foi feita através de medições vibro - acústicas do motor em marcha lenta. Os dados calculados do erro de transmissão e dos sinais medidos foram confrontados obtendo-se convergência. Uma análise de qualidade sonora, por meio de teste de júri, foi realizada para verificar o impacto do ruído de engrenamento na qualidade sonora
Abstract: The requirements of sound quality are increasingly being used in medium and heavy trucks market. Then, owners of vehicles fell troubled by whine noise. The study of whine noise in this thesis is based in one geared pair of a heavy duty diesel engine for vehicular application. As a first approach the transmission error of the gears was calculated by the deformations of the teeth under load (compliance), according to literature, the transmission error peak to peak amplitude, had directly correlation with the whine noise. The proofing of this influence was performed through vibro-acoustics measurements of the engine in low idle. The calculated data of transmission error and processed measurements signals were confronted, obtaining convergence. A sound quality analysis, by juri test, was performed to verify the impact of the whine noise in sound quality
Mestrado
Dinâmica
Mestre em Engenharia Automobilistica

Induction motors are widely used in industrial processes. The malfunction of a motor may not only lead to high repair costs, but also cause immense financial losses due to unexpected process downtime. Since thermal overload is one of the major root causes of stator winding insulation failure, an accurate and reliable monitoring of the stator winding temperature is crucial to increase the mean time to catastrophic motor breakdown, and to reduce the extraordinary financial losses due to unexpected process downtime. To provide a reliable thermal protection for induction motors fed by motor control devices, a dc signal-injection method is proposed for in-service induction motors fed by soft-starter and variable-frequency drives. The stator winding temperature can be monitored based on the estimated stator winding resistance using the dc model of induction motors. In addition, a cooling capability monitoring technique is proposed to monitor the cooling capability of induction motors and to warn the user for proactive inspection and maintenance in the case of cooling capability deterioration. The proposed cooling capability monitoring technique, combined with the proposed stator winding temperature monitoring technique, can provide a complete thermal protection for in-service induction motors fed by motor control devices. Aside from online thermal protection during a motor's normal operation, the thermal protection of de-energized motors is also essential to prolong a motor's lifetime. Moisture condensation is one of the major causes to motor degradation especially in high-humidity environments. To prevent moisture condensation, a non-intrusive motor heating technique is proposed by injecting currents into the motor stator winding using soft-starters. A motor's temperature can be kept above the ambient temperature due to the heat dissipation, so that the moisture condensation can be avoided. To sum up, active stator winding temperature estimation techniques for induction motors under both operating and de-energization conditions are proposed in this dissertation for both thermal protection and optimizing the operation of a motor system. The importance of these proposed techniques lies in their non-intrusive nature: only the existing hardware in a motor control device is required for implementation; a motor's normal operation is not interrupted.

Passive components like resistors, capacitors and inductors are used in every electronic system. These are the very basic components which affect the system performance at higher frequencies and it is necessary to understand and model the behavior of these components in a very accurate manner. This work focuses on utilizing Printed Circuit Board (PCB) test boards, or fixtures, made of FR4 for characterizing Surface Mount Device (SMD) components. Agilent's Advanced Design System (ADS) microwave circuit simulation software was used for designing the microstrip transmission lines as well as for generating the layout for manufacturing of the PCB. SMD resistors, capacitors and inductors were soldered into the fixture and then measured using the Vector Network Analyzer (VNA). The calibration kit was developed in ADS. The measured data were calibrated using the TRL (Thru-Reflect-Line) calibration algorithm. A calibration kit consisting of through, three transmission lines of various lengths, open and short was designed and manufactured. Calibration procedures were performed using Cascade Microtech's WinCal XE software. Based on our experience, TRL calibration did not perform to its full potential due to errors in the value of the characteristic impedance of microstrip transmission line. This impedance is ideally assumed to be 50 Ohm, but our lines had characteristic impedance of around 49 Ohm. Simple models for the resistors and capacitors were developed by our collaborators at the University of Zagreb and we developed the model for the inductors. We used ADS for simulations and comparison with the measured data. Extensive optimization of these models was done so as to fit the measured and modeled data. As the frequency goes above 4 GHz models and measurements don't match due to the limitations of the PCB material, the increasing effects of the parasitics and calibration artifacts. This work shows how and when we can use inexpensive FR4 PCB for the characterization of the passive SMD components in the low GHz frequency range. It also examines the range of operating frequency of SMD components, verifies the parameters extracted from the simple model and tests the TRL calibration algorithm.

This thesis examines how Flexible AC Transmission Systems (FACTS) devices can improve the secure-economic operation of a power system. More specifically, the benefits of FACTS devices in a network are evaluated in terms of four areas of power system study: system security, economic dispatch operation, maximum network loadability and electric industry deregulation. Simulations of a simple network are made to evaluate how a FACTS device can be used to increase the security region of a network. Based on this analysis, simulations are performed using the 24-bus IEEE reliability test network to assess the possible savings in generation costs, the increase in maximum network loadability and the improvements in flexibility of exchanges resulting from the use of a FACTS device in this network. The results demonstrate that FACTS devices can be used effectively to increase the security region of a network thereby allowing for a better optimum operating point in any optimization problem performed over such a region.

It is specifically important to focus on voltage stability analysis of the power system to avoid worst case scenarios such as voltage collapse. The purpose of this thesis is to identify methods for enhancing the steady-state voltage stability using FACTS devices and determining their impact on real and reactive power losses, improvement of bus voltage magnitude, and transmission line loadability. To achieve this, FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), and Thyristor Controlled Series Capacitor (TCSC) are used in the test system as three separate test cases. The results obtained assist in drawing conclusions on the effectiveness of each FACTS devices at generator, load and swing buses, on lines between two load buses, and between a load bus and a generator bus, in terms of metrics such as voltage magnitude profile, PV curves, and active and reactive power losses.

Orientador: Robson Pederiva
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho desenvolve-se um método, que permite avaliações de parâmetros, para o estudo do projeto de um sistema auto-tensionador no controle de suas vibrações transversais e forças atuantes. Parâmetros construtivos e operacionais, como: a geometria, inércia, rigidez da mola do auto-tensionador, rigidez da correia e condições de operação, como: frequências de excitação, forças estáticas e dinâmicas são obtidas em um sistema auto-tensionador de transmissão por correias, aplicados em automóveis de passeio comerciais. Com a modelagem dinâmica de um grau de liberdade, calcula-se a força de atrito e fator de amortecimento, que estabelece o controle de vibrações e forças atuantes no sistema. Os resultados das simulações computacionais são analisados e comparados com os resultados obtidos pelo protótipo experimental desenvolvido. Os resultados tecno-experimentais indicam ajuste satisfatório, o que representa uma contribuição significativa, para o estudo de sistemas auto-tensionadores e na melhoria do controle de vibrações e forças atuantes em correias dentadas, em tempo real de projeto.
Abstract: This investigation describes a method, which permits evaluating the best parameters, in the study of tensioner project system in its transversal vibration control and actuating forces. The construtive and operating parameters, as: geometry, inertia, tensioner spring stiffness, belt stiffness, and operating conditions as: excitation frequencies, estatic and dinamic forces are obtained in a tensioner of transmition by belts with market vehicles aplication. With a dinamical modelling of one degree of fredow are calculated the atrict force and damping factor that establish the vibration control and system actuating forces. The computational simulating results are analysed and compared with obtained results from the developed experimental prototype. The tecno-experimental results have a satisfactory adjust, that represents a significative contribution, for tensioners systems study and the better control of vibrations and actuating forces on driven belts, in project real time.
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

This work presents a novel methodology for evaluation of in service loads applied to the output shafts of automatic transmissions. It also presents a novel methodology of data reduction for shaft load signals as an alternative to the cycle counting methods. Current durability testing of automatic transmission output shafts uses 50 000 stall torque cycles from zero to wide open throttle. In the majority of cases, these requirements lead to an over design that can result in an unnecessarily bulky transmission system. As a solution to this problem a novel methodology for evaluation of loads applied to the output shafts of automatic transmissions was developed. The methodology is based on real world loading conditions and therefore leads to a more realistic estimation of the fatigue life of shafts. The methodology can be used as a tool for shaft optimisation in different drive conditions. Using the developed methodology the effects of different road conditions on the fatigue life of a transmission output shaft were compared. Four routes having differing driving conditions were investigated and of those routes, the route with most stop-start events resulted in the greatest reduction in fatigue life. A novel methodology of data reduction for shaft load signals was also developed. The methodology is based on knowledge of the bandwidth and dynamic range of the expected in-service load signal. This novel methodology allows significant reduction of the volume of data to be acquired. It preserves the time sequence of peaks and valleys of the signal, which is vital in the case of fatigue analysis. This is in contrast to current methods based on cycle counting. Cycle counting methods achieve high data reduction but do not preserve the time sequence of the signal. The developed novel methodology has been validated on the newly developed data acquisition system capable of real time data acquisition and compression of shaft torque signal. The performed tests show that the proposed one-channel low cost system equipped with 1 GB compact flash card can store well over 10 000 hrs of load history.