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In step with development of advanced, cost effective semiconductors and electrical motor drive components, the Switched Reluctance Machine (SRM) has become the center of public attention. Interest in a single-phase SRM has arisen in many places, especially because of its low cost applications. However, some drawbacks have plagued single-phase SRM: the lack of self-starting capability and restricted operation conditions. This thesis presents a four-quadrant operation SRM drive system with a single controllable switch for two phase configuration. The SRM's configuration has four main stator poles, four rotor poles, and four auxiliary stator poles. Because of this special arrangement, a four-quadrant operation with a given power converter topology and proposed control algorithms has been realized. The focus of the paper is to realize a four-quadrant operation with a single-switch converter based SRM. In addition, this research resulted in a new self-starting scheme without adding permanent magnets. Simulation results and experimental results utilizing the control algorithm verify the performance of the system. / Master of Science

Current access strategies for minimal interface (e.g., binary switch) users employ time-coded (i.e., synchronous) protocols that map unique sequences of user-generated binary digits (i.e., bits) to each of the available outcomes of a device under control. With such strategies, the user must learn and/or reproduce the timing of the protocol with a certain degree of accuracy. As a result, the number, κ, of device outcomes made accessible to the user is typically bound by the memorization capacity of the latter and by the time required to generate the appropriate bit sequences. Furthermore, synchronous access strategies introduce a minimum time delay that increases with larger κ, precluding access to control applications requiring fast user response. By turning control on its head, this thesis presents an access method that completely eliminates reliance on time-coded protocols. Instead, the proposed asynchronous access method requires users to employ their interfaces only when the behavior of the device under control does not match their intentions. In response to such event, the proposed method may then be used to select, and automatically transmit, a new outcome to the device. Such outcome is informed by historical and contextual assumptions incorporated into a recursive algorithm that provides increasingly accurate estimates of user intention. This novel approach, provides significant advantages over traditional synchronous strategies: i) the user is not required to learn any protocol, ii) there is no limit in the number of outcomes that may be made available to the user iii) there is no delay in the response of the device, iv) the expected amount of information required to achieve a particular task may be minimized, and, most importantly, v) the control of previously inaccessible devices may be enabled with minimal interfaces. This thesis presents the full mathematical development of the novel method for asynchronous control summarized above. Rigorous performance evaluations demonstrating the potential of this method in the control of complex devices, by means of minimal interfaces, are also reported.

Current access strategies for minimal interface (e.g., binary switch) users employ time-coded (i.e., synchronous) protocols that map unique sequences of user-generated binary digits (i.e., bits) to each of the available outcomes of a device under control. With such strategies, the user must learn and/or reproduce the timing of the protocol with a certain degree of accuracy. As a result, the number, κ, of device outcomes made accessible to the user is typically bound by the memorization capacity of the latter and by the time required to generate the appropriate bit sequences. Furthermore, synchronous access strategies introduce a minimum time delay that increases with larger κ, precluding access to control applications requiring fast user response. By turning control on its head, this thesis presents an access method that completely eliminates reliance on time-coded protocols. Instead, the proposed asynchronous access method requires users to employ their interfaces only when the behavior of the device under control does not match their intentions. In response to such event, the proposed method may then be used to select, and automatically transmit, a new outcome to the device. Such outcome is informed by historical and contextual assumptions incorporated into a recursive algorithm that provides increasingly accurate estimates of user intention. This novel approach, provides significant advantages over traditional synchronous strategies: i) the user is not required to learn any protocol, ii) there is no limit in the number of outcomes that may be made available to the user iii) there is no delay in the response of the device, iv) the expected amount of information required to achieve a particular task may be minimized, and, most importantly, v) the control of previously inaccessible devices may be enabled with minimal interfaces. This thesis presents the full mathematical development of the novel method for asynchronous control summarized above. Rigorous performance evaluations demonstrating the potential of this method in the control of complex devices, by means of minimal interfaces, are also reported.

O emprego de tecnologias de acesso a comunicação, baseados em métodos de acesso por escaneamento, viabiliza novas oportunidades de comunicação para indivíduos com disfunção motora severa. Um dos exemplos mais comuns desse tipo de tecnologia é o teclado virtual operado por varredura. Teclados virtuais são frequentemente utilizados como dispositivos de comunicação aumentativa e alternativa por indivíduos com restrições motoras graves e que apresentam comprometimento da fala e da escrita. São compostos por uma matriz de teclas e simulam a operação de um teclado físico para a composição de mensagens. Uma das limitações desses sistemas é o baixo desempenho que possuem. Taxas de comunicação lentas e a considerável ocorrência de erros são alguns dos problemas que usuários desses dispositivos sofrem durante o uso diário. O desenvolvimento e a avaliação de novas estratégias em comunicação aumentativa e alternativa são essenciais para a melhoria das oportunidades de comunicação dos usuários que fazem uso desse tipo de tecnologia. Neste sentido, este trabalho explora diferentes estratégias para aumentar essa taxa de comunicação e reduzir os erros cometidos por seus usuários. Análises computacionais e práticas foram executadas para a avaliação das estratégias propostas. / The use of access technologies for communication, based on scanning methods, enables new communication opportunities for individuals with severe motor dysfunction. One of the most commom examples of this type of technology is the single switch scanning. Single switch scanning keyboards are often used as augmentative and alternative communication devices for inidividuals with severe mobility restrictions and with compromised speech and writing. They consist of a matrix of keys and simulate the operation of a physical keyboard to write messages. One of the limitations of these systems is their low performance. Low communication rates and considerable errors ocurrence are some of the few problems that users of these devices suffers during daily use. The development and evaluation of new strategies in augmentative and alternative communication are essential to improve the communication opportunities of user who make use of such technology. Thus, this work explores different strategies to increase communication rate and reduce user’s mistakes. Computational and practical analysis were performed for the evaluation of proposed strategies. / Dissertação (Mestrado)