Thesis (M.Sc.)--York University, 2005. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 110-116). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11860

Made available in DSpace on 2014-06-11T19:30:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-22Bitstream added on 2014-06-13T21:01:22Z : No. of bitstreams: 1 sanches_maa_dr_ilha.pdf: 2562383 bytes, checksum: 66a80f3f2d12c4eda097cd3b1860fbca (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Foi implementado um sistema eletrônico de eletroestimulação funcional para geração e avaliação de movimentos nos membros inferiores de pessoas paraplégicas e hígidas. O sistema eletrônico é constituído por um estimulador elétrico neuromuscular, por uma plataforma de testes e por algoritmos de controle. O estimulador é de oito canais, independentes, controlado, com forma de onda de corrente de estimulação bifásica, retangular, com carga balanceada e capacidade de fornecer até 140 mA. O sistema pode operar com modulação por largura ou amplitude ou de pulso. Os parâmetros de estimulação podem ajustados e alterados com facilidade e agilidade por meio tela de do computador em um programa desenvolvido em LabVIEW. Foi necessária a implementação de uma plataforma de testes que contém os dispositivos necessários para gerar e aferir algumas grandezas, como estímulos elétricos controlados, deslocamento, velocidade e aceleração angular. A plataforma é composta por sensores, circuitos de condicionamento de sinais, software para o ajuste e controle dos parâmetros de eletroestimulação e também uma cadeira onde foi instalada toda a instrumentação. Utilizou-se DSP (Processador Digital de Sinais) e LabVIEW, juntamente com o eletroestimulador e sensores, para a implementação de controladores em malha fechada, PID (Proporcional Integral e Derivativo) e também Fuzzy Takagi-Sugeno, para estabelecer a posição da perna do na posição desejada, no movimento de extensão do joelho, de pessoas hígidas e paraplégicas. Foram realizados testes em malha aberta e malha fechada, com voluntários hígidos e paraplégicos. Modelos Fuzzy Takagi-Sugeno (TS) foram utilizados na modelagem e controle discreto do modelo matemático proposto por Ferrarin e Pedotti (2000). Foi proposta uma metodologia inédita para a... / We have implemented an electronic system for functional electrical stimulation for generation and evaluation of movements in the lower limbs of paraplegic and healthy people. The electronic system comprises a neuromuscular electrical stimulator, a test platform and control algorithms. The eight-channel stimulator is independent, controlled, waveform for stimulating current biphasic, rectangular, and load-balanced ability to deliver up to 140 mA. The system can operate with width or amplitude modulation or pulse. The stimulation parameters can be easily and agility adjusted and changed through the computer screen in a program developed in LabVIEW. It was necessary to implement a test platform that contains the necessary devices to generate and measure some quantities such as controlled electrical stimulation, displacement, velocity and angular acceleration. The platform consists of sensors, signal conditioning circuits, software for adjustment of parameters and control of electrostimulation and also a chair where it was settled the instrumentation. We used DSP (Digital Signal Processor) and LabVIEW, together with the electrostimulator and sensors to implement a closed loop controllers, PID (Proportional Integral Derivative) and Fuzzy Takagi-Sugeno, to establish the position of the leg in a desired position, in the movement of knee extension in people. Tests were conducted in open and closed loop with healthy and paraplegic volunteers. Takagi-Sugeno (TS) fuzzy models were used for modeling and discrete control of the mathematical model leg proposed by Ferrarin e Pedotti (2000). We proposed a new methodology for the construction of local models considering the position, velocity and angular acceleration. The... (Complete abstract click electronic access below)

O objetivo deste estudo é desenvolver um método para avaliar a confiabilidade de sistemas eletrônicos complexos. A análise proposta baseia-se na aplicação de ensaios de confiabilidade e de normas técnicas, bem como modelos matemáticos para estimação da vida operacional. Os ensaios de confiabilidade executados nesse estudo simulam condições operacionais mais severas que as usualmente enfrentadas pelo sistema, a fim de reduzir o tempo de execução dos ensaios. Ao longo destes, foram coletados os tempos até a falha de diversas amostras do sistema, os quais são submetidas a diferentes condições de operação. O planejamento das variáveis que aceleram os principais modos de falha de componentes eletrônicos e os perfis de solicitação empregados também são discutidos, sendo consideradas as mais importantes a temperatura e a umidade. Através da aplicação de modelos matemáticos para predição da vida nas condições normais de operação, dadas as ocorrências de falhas nas condições aceleradas, a confiabilidade e o tempo médio até a falha são determinados para a central telefônica estudada, tomada como exemplo na aplicação do método. Adicionalmente aos ensaios são desenvolvidas estimativas da confiabilidade da central telefônica através da norma militar US MIL-HDBK-217 F (1991). Os resultados destas estimativas são utilizados para comparação e confirmação dos resultados obtidos através dos ensaios. Destaca-se que os métodos descritos neste texto não são restritos a aplicação em centrais telefônicas analógicas, mas podem ser empregados a uma grande família de equipamentos eletrônicos de complexidade tecnológica semelhante. / This research aims to develop a method to evaluate the reliability of complex electronic systems. The analysis proposed is based on application of reliability laboratory tests, technical standards and mathematical models to estimate the system operational life. Reliability tests proposed simulate harder operational conditions than those usually faced by the system, aiming to reduce the time of execution. During the tests, time to failure of several samples are collected. Those samples are submitted to different environmental conditions. Selection of variables that accelerate the main failure modes of electronic components and the load profiles used are also analyzed, considering humidity and temperature the most important variables for failure acceleration. The proposed model is used to estimate the reliability and the mean time to failure of an analog PABX, those values being generated by the application of mathematical models for life prediction in the usage operation condition, given the accelerated reliability estimate. Additionally to the tests, a reliability estimation of the PABX central is done using US MIL-HDBK-217 F (1991). Results are used to compare and to validate the reliability value evaluated through the accelerated tests. It is important to emphasize that the application of the methods described in this present text is not restricted to analog PABX systems, being applied to a wide range of electronic equipments with similar technological complexity.

Ph.D. / The work presented in this dissertation is concerned with the application of Chaos Theory to the field of Electrical and Electronic Engineering. A comprehensive study on electrical and electronic systems which exhibit chaotic behaviour, forms an integral part of this work. The objective of this survey is, firstly, to assess how widely chaos occurs in the field of electrical engineering. Secondly, the survey attempts to determine how successfully chaotic behaviour (in electrical systems) is identified and characterized. Finally, the survey aims to determine to what extent nonlinear phenomena and specifically chaos is applied to solve engineering problems. From this survey it is concluded that the study of chaos in electronics has reached a mature state. Currently, research focuses on controlling chaos, finding new applications of chaos as well as using chaos theory to gain a better understanding of the nonlinear world we live in. The other component of this dissertation consists of research done in the field of electronics. Contributions are made in controlling chaos and the analysis of chaotic systems both analytically and numerically.

A new microprocessor based synchronous switch has been developed at Virginia Tech as an improvement on the customary solid state electronic or mechanical switch. The author designed and built a 16-pole synchronous switch using a 16 bit microprocessor to provide programmable control on both the opening and closing times for each of the 16 poles of the switch. The user can define a sequence of states (short circuit and open circuit) for each of the 16-poles with control on a) The instant of shorting. b) The instant of opening. The above single shot action can be made repetitive by defining a period of repetition. The device is particularly useful in power system projects and has a unique place in repetitive and 'one time' switching in power system models. The switch is totally self-contained and can be operated through a terminal interfaced to an 8086 microprocessor based microcomputer. The microcomputer was developed and is dedicated to this application alone. The use of 8086 microprocessor facilitates realization of a relatively trouble free, noiseless operation. The system design contains a zero-crossing detector circuit which is used to interrupt the microcomputer for synchronisation. The system has buffered output ports which are connected to mercury wetted relays. These relays are controlled for ON and OFF operation by the user through the above system. The smallest short circuit duration of the order of 2 to 3 msecs can be achieved as determined by the mercury wetted relays. The switch can be used for any purpose where it is desired to accurately control switching points (opening, closing or faulting) on any low power AC network. The switch can be quite useful in studying transient phenomena on three-phase system models. The switch is useful in studying responses of various relaying schemes where it is desirable to test the relay at precise switching angles. Additionally, the switch would be very useful to test or operate circuit breaker models in the power simulation laboratory. / M.S.

No description available.

<p>This master thesis is a portion of the DySCAS project and work is performed at Enea AB. DySCAS (Dynamically Self-Configuring Automotive Systems) is a research project funded by the European</p><p>This thesis concentrates on future vehicle electronic systems. During a life cycle of the car vehicle manufacturers desire to upgrade or add new functions into the vehicle electronic systems, this is not possible with the static-runtime environment that employed into today’s car.</p><p>To tackle this difficult problem many technologies were gathered and a dynamically self-configuring automotive system was introduced by combining technologies like self-managing, service-based and middleware.</p><p>The obtained results fulfilled most of DySCAS requirements. However, the system has a few limitations and these are caused by the immature of distributed reconfigurable embedded systems in the market.</p>

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2017 / Following the involvement in a project where a bank implemented an electronic inventory management system, a need was identified for further research into the human elements influencing the success of such projects. An initial high level study of some available literature supported the idea of human factors playing an important role. The subsequent research question formulated was: What are the major human factors that influence the implementation of electronic systems to replace their manual paper-based counterparts, if any? From literature the major human factors to be analysed were identified as:  Leadership  Communication  Environment and culture  Change readiness By employing a mixed method research approach and analysing the change readiness assessment surveys, post-implementation surveys, project team observations and site key performance indicators (KPIs) of 3 implemented sites, these were all confirmed as factors influencing such implementations. These conclusions were graphically depicted in a proposed framework showing the relationship between leadership as the driving factor to influence culture and change readiness through communication. / MT2018

Power electronics have a significant role in modern electrical devices, for instance, hybrid electric vehicles. Power electronics are the technology in between the source and the load circuits and can convert the power from dc to ac or from dc to ac. There are also many types of dc-dc converters, like such as boost and buck converters, which exhibit switching ripple behavior. A boost converter increases the output voltage (with respect to the input voltage) and reduces the output current. A buck converter decreases the output voltage and increases the output current. Many models are used to predict the behavior of the boost and buck converters. The detailed (DET), state-space averaged (SSA), and generalized averaging method (GAM) models are capable of predicting the average behavior of dc-dc converters. For DET and GAM models, the rippling behavior can also be predicted. These models differ in terms of required run time, existence of constant equilibrium points, and accuracy. The DET model has a long run time and does not have constant equilibrium, but it is very accurate. The SSA technique is a mathematical and time-invariant model that capable of describing the behavior of a dc-dc boost converters. It can derive the small signal ac equations of a switching converter and is used to illustrate the average behavior of any linear or nonlinear system in converters. The SSA does not take extensive runtime simulation and has constant equilibrium points, and can be applied to continuous, discrete and sample data systems. The GAM model can predict the average and ripple behavior in power electronic systems and has constant equilibrium and fast run time. However, it has a numerical stability issue. The integrator stabilized multifrequency averaging (ISMFA) model is employed to solve the stability issue in the GAM model, but it is a complicated dynamic method and has restrictions in its process. In the present study, a simplified but stable GAM model is introduced to predict the average and ripple behavior of boost dc-dc converters and to overcome the limitations of other methods. In this work, the stabilized GAM model has been used for a dc-dc boost converters. The stability of the proposed model is analyzed. The performance of the improved GAM model is compared with the DET, SSA, and GAM models. The results show that the stabilized GAM model is stable with the additional poles created by the GAM assignable by parameter choice. The new GAM model predicts the same results as the existing GAM method without the underlying stability concerns. The stabilized GAM model exhibits constant ii equilibrium point and requires significantly lower run times than the DET model, but it is also able to predict the ripple performance of the converter. The stabilized GAM model does not take a long run time, is less complicated, has fewer restrictions, has constant equilibrium and internal stability, and has more straightforward implementation than other models, like the ISMFA model. It represents a suitable alternative to DET models when high accuracy simulations are desired without long simulation run times.

<p>The technological development is enabling production of increasingly complex electronic systems. All those systems must be verified and tested to guarantee correct behavior. As the complexity grows, testing is becoming one of the most significant factors that contribute to the final product cost. The established low-level methods for hardware testing are not any more sufficient and more work has to be done at abstraction levels higher than the classical gate and register-transfer levels. This thesis reports on one such work that deals in particular with high-level test generation and design for testability techniques.</p><p>The contribution of this thesis is twofold. First, we investigate the possibilities of generating test vectors at the early stages of the design cycle, starting directly from the behavioral description and with limited knowledge about the final implementation architecture. We have developed for this purpose a novel hierarchical test generation algorithm and demonstrated the usefulness of the generated tests not only for manufacturing test but also for testability analysis.</p><p>The second part of the thesis concentrates on design for testability. As testing of modern complex electronic systems is a very expensive procedure, special structures for simplifying this process can be inserted into the system during the design phase. We have proposed for this purpose a novel hybrid built-in self-test architecture, which makes use of both pseudorandom and deterministic test patterns, and is appropriate for modern system-on-chip designs. We have also developed methods for optimizing hybrid built-in self-test solutions and demonstrated the feasibility and efficiency of the proposed technique.</p> / Report code: LiU-Tek-Lic-2002:46.