A power assisted wheelchair combines human power, which is delivered by the arms through the pushrims, with electrical motors, which are powered by a battery. Today’s electric power assisted wheelchairs use force sensors to measure the torque exerted on the pushrims by the user. The force sensors in the pushrims are rather expensive and this approach also makes the wheels a little bit clumsy. The objective with this project is to find a new, better and cheaper solution that does not use expensive force sensors in the pushrims. The new power assisted wheelchair will instead only rely on its velocity, which is measured with rotational encoders, as feedback signal and thereby the project name “Torque Sensor Free Power Assisted Wheelchair”. The project consisted of two main parts; an extensive construction part, where an ordinary joystick controlled motorized wheelchair has been rebuild to the new power assisted wheelchair without torque sensors and a development part, where different torque sensor free controllers has been designed, simulated, programmed and tested. The project resulted in a torque sensor free power assisted wheelchair, where the final implemented design is a proportional derivative controller, which gives a very good assisting system that is robust and insensitive to measurement noise. The proportional derivative control design gives two adjustable parameters, which can be tuned to fit a certain user; one parameter is used to adjust the amplification of the user’s force and the other one is used to change the lasting time of the propulsion influence. Since the new assisting control system only relies on the velocity, the torque sensor free power assisted wheelchair will besides giving the user assisting power also give an assistant, which pushes the wheelchair, additional power. This is a big advantage compared to the pushrim activated one, where this benefit for the assistant is not possible.

Shape plays an important role in our everyday life to interpret information about the surroundings whether we are aware or not. Together with visual and auditory information, we are able to obtain and process information for different purposes. Output devices such as monitors and speakers convey visual and auditory information while input devices such as touch screen and microphones receive that information for human machine interaction. Such devices have become commonplace but there has yet to be a fitting input/output device utilizing our haptic perception. Digital Clay is a next generation Human Machine Interface (HMI) device for 2.5D shape input/output via an array of hydraulic actuators. This device potentially has wide applications in the areas of engineering, sciences, medicine, military, entertainment etc. The user can perceive the shape of a computer programmed model in a tangible and concrete manner which means an added realism with the addition of the sense of touch. Conversely, the user can also use Digital Clay as an input device to the computer, by shaping and molding desired shapes on the device, no longer limited to drawing models with a mouse on CAD software. Shape display has been achieved with the current 5x5 prototype at the Georgia Institute of Technology but this research seeks to expand its capability to include haptic feedback and consequently shaping mode. This thesis gives an overview of the current 5x5 prototype and implements 2 commonly used haptic control methods, the admittance control and the impedance control. For implementing the admittance control, actuator displacement and velocity controllers and a proportional integral observer (PIO) are designed. The model-based unknown input observer is a solution for force estimation without added sensors in the actuators. For implementing the impedance control, a novel pressure control technique is designed to provide pressure feedback to the actuators array along with accurate and reliable displacement measurement. Both of the haptic control methods are evaluated, hardware and software limitations are outlined and possible future improvements are suggested.

Boost dc-to-dc converters have very good source interface properties. The input inductor makes the source current smooth and hence these converters provide very good EMI performance. On account of this good property, the boost converter is also the preferred converter for off-line UPF rectifiers. One of the issues of concern in these converters is the large size of the storage capacitor on the dc link. The boost converter suffers from the disadvantage of discontinuous current injected to the load. The size of the capacitor is therefore large. Further, the ripple current in the capacitor is as much as the load current; hence the ESR specification of the tank capacitor is quite demanding. This is specially so in the emerging application areas of automotive power conversion, where the input voltage is low (typically 12V) and large voltage boost (4 to 5) are desired. The first part of this thesis suggests multi-phase boost converter to overcome the disadvantages of large size storage capacitor in boost converter. Comparison between the specification of single stage and multi-stages is thoroughly examined. Besides the average small signal analysis of N converters in parallel and obtaining an equivalent second order system are discussed. By paralleling the converters the design of closed loop control is a demanding task. To achieve proper current sharing among the stages using current control method is inevitable. Design and implementation of closed loop control of multi-phase boost converter both in analog and digital is the topic of next part of the thesis. Comparison between these two approaches is presented in this part and it will be shown that digital control is more convenient for such a topology on account of the requirement of synchronization, phase shifted operation, current balancing and other desired functions, which will be discussed later in detail. A new direct digital control method, which is simple and fast, is developed. Two different realizations with DSP controller and FPGA controller are considered. In the last part of the thesis a novel soft switching circuit for boost converter is presented. It provides Zero Voltage Switching (ZVS) for the main switch and Zero Current Switching (ZCS) for the auxiliary switch. The paper presents the idealized analysis giving all the circuit intervals and the equations necessary for the design of such a circuit. The proposed soft switching circuit is particularly suited for the tapped-inductor boost circuit with a minimum number of extra components. Extension of the method to tapped inductor boost converter addresses the application of Zero Voltage Transition (ZVT) to high conversion ratio converters. Extension of the method to multiphase boost converter shows that with less number of auxiliary switches soft switching operation can be achieved for all interleaved switching devices. Several laboratory prototype boost converters have been built to confirm the theoretical results and design methods are matching with both simulation and experimental results.

Existem máquinas que necessitam de uma grande velocidade de processamento para seu correto trabalho, essas máquinas possuem um tempo de processamento de resposta crítico. Quando considera-se este aspecto somado à necessidade de um controle do comportamento estático e dinâmico de um sistema chega-se ao controlador com fortes demandas de tempo de execução. Essa dissertação compara controladores discretos implementados em ponto fixo, com diferentes precisões, usando para tanto a simulação do comportamento de controladores confeccionados em linguagem de comandos Matlab e em linguagem VHDL 2008. Esta última está em desenvolvimento e padronização pelo IEEE. A linguagem VHDL é usada nas FPGAs que são dispositivos de alta velocidade e capacidade de processamento paralelo. O principal objetivo do trabalho é o estudo e a implementação de controladores discretos em FPGA com o auxílio da linguagem VHDL 2008, determinando suas virtudes e limitações, em particular quanto à estrutura de programação, análise de erro e a demanda por recursos. Os resultados alcançados demonstram que algumas melhorias ainda precisam ser feitas para que o VHDL 4.0, conhecido como VHDL 2008, seja entregue ao mercado como padrão estável. Entretanto, quando conhecidas suas limitações, já é possível seu uso em implementações com conversão de sinais discretos para analógicos, como é o caso de controle e simulação de sistemas dinâmicos como servomecanismos. / There are machines that need large processing speed for its correct working, these machines have a critical time response processing. When it is considered that aspect coupled with the need for control of static and dynamic behavior of a system arrives at the controller with strong demands on runtime. This dissertation compares discrete controllers implemented in fixed point with different accuracies, using for both the simulation of the behavior of controllers manufactured in Matlab command language and VHDL 2008. VHDL 2008 still in development and standardization by the IEEE. The VHDL language is used in FPGAs that are high speed devices with parallel processing capability. The main objective of this work is the study and implementation of discrete controllers in FPGA with the help of the VHDL 2008 language, determining its strengths and limitations, particularly in regard to the structure of programming, error analysis and demand for resources. Results show that accuracy still need some improvements a standard to the VHDL 4.0, known as VHDL 2008, is delivered to the market a stable standard. However, knowing it limitations, it is possible implementations and use in conversion of analog signals to discrete, such as control and dynamic systems simulation like servomechanisms.

Made available in DSpace on 2014-06-11T19:30:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-08-30Bitstream added on 2014-06-13T20:47:24Z : No. of bitstreams: 1 ribeiro_jms_me_ilha.pdf: 1485185 bytes, checksum: 5ab0628a95f1aed7502862f70ee550ce (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta três novas estratégias de controle discreto. O enfoque principal do trabalho foi dado ao Controle Discreto com Modos Deslizantes (CDMD) aplicados em sistemas que possuem atraso no processamento do sinal de controle. As novas estratégias de controle objetivam a elaboração de leis de fácil implementação prática e que ao mesmo tempo sejam robustas a incertezas da planta. Uma característica destas novas abordagens para controle discreto com atraso no tempo é a utilização de um Controle com Modos Deslizantes sem a necessidade de predição do sinal de controle. Os métodos de projeto propostos podem ser aplicados no controle de plantas estáveis ou instáveis com atraso no sinal de controle. Uma das estratégias foi elaborada para realizar controle apenas em sistemas discretos que não possuem atraso no sinal de controle, enquanto que as demais são utilizadas para controle em sistemas com atraso. São apresentadas simulações e resultados de implementações práticas, sobre uma planta estável de Controle Automático da Geração (CAG) e sobre um Sistema Pêndulo Invertido, que caracteriza bem uma planta instável. Os resultados comprovam a eficácia dos novos controladores. / This work presents three new strategies of discrete-time control. The main focus of the work was given to the Sliding Mode Control (SMC) applied in systems that present delay in the processing of the control sign. The new control strategies provide laws of control of easy practical implementation and that at the same time are robust to uncertainties of the plant. A characteristic of these new approaches, for discrete-time control with delay-time, is the use of a Sliding Mode Control without the need of prediction of the control signal. The proposed design methods can be applied in the control of stable or unstable plants, with delay in the control signal. One of the strategies was elaborated to accomplish control just in discrete-time system without delay-time in the control sign, while the others are used for control in systems with delay-time. Simulations and experimental results are shown on a stable plant of Automatic Generation Control (AGC) and on Inverted Pendulum System, that is an unstable plant. The results prove the controllers' effectiveness.

Dans ce travail nous cherchons à développer des algorithmes de commande adaptés au fonctionnement à haute vitesse d’une machine synchrone à aimants permanents (MSAP) et de son onduleur en optimisant l’efficacité énergétique de l’ensemble. Bien que la vocation soit très large, le domaine de la traction électrique est priorisé. Les MSAP tournant à haute vitesse sont de plus en plus utilisées dans les véhicules électriques en raison de leur forte densité de puissance. La haute vitesse implique une force électromotrice élevée et requiert la réduction du flux (défluxage) dans l’entrefer. Lors d’un fonctionnement de la machine en régime défluxé, si la contribution de l’aimant peut-être totalement compensée alors nous pouvons utiliser une stratégie Maximum Torque Per Volt (MTPV) pour générer les consignes de courant qui respectent les limites électriques théoriques quelle que soit la vitesse de rotation de la machine. En l’absence de boucle de vitesse, le couple de référence doit être limité aux points de fonctionnement atteignables, calculés en fonction des limites de courant (limites onduleur et machine), tension (batterie) et puissance (batterie et partie mécanique). Nous proposons ainsi dans cette thèse de calculer les références de courant avec une stratégie MTPA (Maximum Torque Per Ampere) à basse vitesse et d’utiliser un algorithme de défluxage basé sur une régulation de la norme de la tension associée à une stratégie MTPV à haute vitesse sans commutation d’algorithme mais par une action continue sur la valeur de la saturation de courant. Concernant la boucle de courant nous réalisons une commande numérique dans le repère d-q qui tient compte de la discrétisation, du retard (dû au temps de calcul), et du fort couplage inter-axes à haute vitesse sous des critères de précision, stabilité et rapidité. Nous étudions les stratégies de découplage minimal et de découplage discret avec prédiction de la variation du courant. Les approches par régulateurs avec structure RST et par commande prédictive-optimale sont développées. Une prédiction de la position réelle du rotor est incluse afin de conserver la stabilité à haute vitesse. Finalement nous réalisons une maquette avec une MSAP à échelle réduite sur laquelle nous testons ces stratégies de commande. Nous validons par expérience que l’algorithme proposé dans la thèse est capable de piloter la machine à haute vitesse en respectant les limites électriques et nous vérifions qu’il améliore les performances (couple, vitesse maximale, pertes) obtenues à haute vitesse. / In this work we search to develop control algorithms adapted to the high speed operation of a permanent magnet synchronous motor (PMSM) and its inverter by optimizing the energy efficiency of the set. Although the vocation is very broad, the field of electric traction is prioritized. High speed PMSMs are increasingly used in electrical vehicles because of their high power density. The high speed implies a high electromotive force and requires the reduction of the flux (fluxweakening) in the air gap. When the motor is running in flux-weakening mode, if the contribution of the magnet can be fully compensated then we can use a Maximum Torque Per Volt (MPTV) strategy to generate the current references that meet the theoretical limits regardless of the machine rotation speed. In the absence of a speed loop the reference torque must be limited to the achievable operating points, calculated according to the current limits (inverter and machine limits), voltage (battery) and power (battery and mechanical part). We propose in this thesis to calculate the current reference with Maximum Torque Per Ampere (MTPA) strategy at low speed and to use a flux-weakening algorithm based on a regulation of the voltage norm associated with a MTPV strategy at high speed without switching algorithms but by a continuous action on the value of the current saturation. Concerning the current loop, we carry out a numerical control in the d-q frame which takes into account the discretization, the delay (due to the computation time), and the high inter-axis coupling at high speed under criteria of precision, stability and speed. We study the strategies of minimal decoupling and discrete decoupling with prediction of the variation of the current. The approaches by regulators with RST structure and predictive-optimal control are developed. A prediction of the actual rotor position is included to maintain the stability at high speed. Finally a real model with a reduced scale PMSM is realized on which these control strategies are tested. We validate by experiment that the algorithm proposed in the thesis is able to control the machine at high speed respecting the electrical limits and verify that it improves the performances (torque, maximum speed, losses) obtained at high speed.

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-09-25Bitstream added on 2014-06-13T19:26:47Z : No. of bitstreams: 1 leandro_e_me_ilha.pdf: 1745578 bytes, checksum: 2db70f1465f9f7258fdbcda3cdebf72c (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta uma nova proposta para sistema de refrigeração com controle dinâmico de temperatura, operando com estrutura de compressor aberto, acionado por motor de indução trifásico com velocidade variável, e estágio de entrada retificador com correção ativa do fator de potência. O estágio de entrada é composto por um retificador Boost monofásico com elevado fator de potência, com duas células entrelaçadas, operando no modo de condução crítica, empregando técnica de comutação não dissipativa e controlado por dispositivo FPGA, associado a um estágio de saída inversor de dois níveis convencional trifásico à IGBT, o qual é controlado por um Processador Digital de Sinais (DSP - Digital Signal Processor). A técnica de comutação não dissipativa para o estágio de entrada é baseada em células ZCS (Zero-current-switching). As principais características do retificador incluem a redução da ondulação da corrente de entrada, redução da ondulação da tensão de saída retificada, utilização de componentes com reduzidos esforços, reduzido volume do filtro de entrada para Interferências Eletromagnéticas (EMI - Electromagnetic Interference), elevado Fator de Potência (FP) e reduzida Distorção Harmônica Total (DHT) da corrente de entrada, atendendo os limites da norma IEC61000-3-2. O controle digital para o estágio de saída inversor foi desenvolvido usando duas diferentes técnicas, incluindo a técnica convencional controle escalar Volts/Hertz (V/Hz) e o controle Vetorial com Orientação pelo Fluxo do estator, com o propósito de verificar a aplicabilidade e a performance dos controles digitais propostos, para o controle contínuo da temperatura, aplicados a um protótipo de sistema de refrigeração. / This work presents a new proposal for refrigeration systems with dynamic control of temperature, working with structure of open compressor, driving a three-phase induction motor with variable speed, and input rectifier with active power factor correction. The proposed system is composed of a single-phase high-power-factor boost rectifier, with two cells in interleaved connection, operating in critical conduction mode, and employing a softswitching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifier s features include reduction in input current ripple, reduction in output voltage ripple, use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output stage inverter has been developed using two different techniques, the conventional Voltage-Frequency control (scalar V/Hz control), and a simplified stator oriented vector control, in order to verify the feasibility and performance of the proposed digital controls, for continuous temperature control, applied at a refrigerator prototype.

Made available in DSpace on 2016-12-12T17:38:37Z (GMT). No. of bitstreams: 1 RESUMO - Josue.pdf: 8954 bytes, checksum: 37d4018bcbba745d53a694b1e3fad11b (MD5) Previous issue date: 2009-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work shows a unified power quality conditioner based on a digital controlier. Such conditioner is composed of shunt active power filter, to compensate the input une current, and series active power filters to compensate the load voltage. The proposal consist in applying a simple control strategy based on direct comparison the input une current and load voltãge waveforms with sinusoidal references. Initially is presented a study about the active power conditioner characteristics, classification and topologies, foliowing UPQC power structure is explored, as converter definition, aspects for grid connection and analysis and project at passive filters. Afterwards, the mathematicál models are derived, the controllers are defined and simulations are performed. Finaily, the results obtained with UPQC practical tests are shown. / Este trabalho apresenta um condicionador unificado de qualidade de energia (UPQC) controlado digitalmente. Tal condicionador é composto por um filtro ativo paralelo, para compensar a corrente na rede, e um filtro ativo série, para compensara tensão na carga. A proposta consiste em aplicar uma estratégia de controle simples baseada na comparação direta da corrente na rede e tensão na carga com referências senoidas. Inicialmente é apresentado um estudo a respeito das topologias e classificação dos condicionadores de energia, em seguida é explorada a estrutura de potência do UFQC, como definição do conversor, aspectos relacionados à conexão com a rede e anAlise e projeto dos filtros passivos. Posteriormente são obtidos os modelos matemáticos, projetados os controladores e elaboradas simulações para, finalmente apresentar os resultados obtidos com os ensaios do UPQC.

Made available in DSpace on 2016-12-12T17:38:37Z (GMT). No. of bitstreams: 1 Luis Mariano Nodari.pdf: 2083674 bytes, checksum: f3c4bf3291e2d0a7c63bb7bea7118f85 (MD5) Previous issue date: 2011-05-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work proposes a digital control system for a half-bridge boost rectifier, which composes the input stage of a single-phase transformerless double-conversion UPS. The proposed control system has an inner current loop and two outer voltage loops to maintain near unity input power factor and to regulate the dc bus voltages. The control loops operate with distinct sampling frequencies, so that current loop operates with high sampling frequency, and voltage loops operate with reduced sampling frequency and moving average filters to improve the dynamic response, without affecting the input power factor. Simulation and experimental results are included to demonstrate the performance of the closed-loop system even under severe load conditions. / Esta Dissertação de Mestrado propõe um sistema de controle digital para um retificador meiaponte monofásico, que integra o estágio de entrada de uma UPS não isolada de dupla conversão monofásica. O sistema de controle proposto tem uma malha de corrente interna e duas malhas de tensão externas para manter o fator de potência unitário e regular a tensão no barramento. O controle opera com frequências distintas de amostragem, sendo que a malha de corrente opera com alta frequência de amostragem, enquanto as malhas de tensão operam com baixas frequências e com filtros de média móvel para melhorar a resposta dinâmica das tensões de saída do retificador, sem afetar o fator de potência de entrada. Resultados de simulação e experimentais demonstram o bom desempenho do sistema de controle digital proposto mesmo em condições severas de carga.

Orientador: José Paulo Fernandes Garcia / Banca: Marcelo Carvalho M. Teixeira / Banca: Edvaldo Assunção / Banca: Fuad Kassab Junior / Banca: Marco Henrique Terra / Resumo: Este trabalho apresenta três novas estratégias de controle discreto. O enfoque principal do trabalho foi dado ao Controle Discreto com Modos Deslizantes (CDMD) aplicados em sistemas que possuem atraso no processamento do sinal de controle. As novas estratégias de controle objetivam a elaboração de leis de fácil implementação prática e que ao mesmo tempo sejam robustas a incertezas da planta. Uma característica destas novas abordagens para controle discreto com atraso no tempo é a utilização de um Controle com Modos Deslizantes sem a necessidade de predição do sinal de controle. Os métodos de projeto propostos podem ser aplicados no controle de plantas estáveis ou instáveis com atraso no sinal de controle. Uma das estratégias foi elaborada para realizar controle apenas em sistemas discretos que não possuem atraso no sinal de controle, enquanto que as demais são utilizadas para controle em sistemas com atraso. São apresentadas simulações e resultados de implementações práticas, sobre uma planta estável de Controle Automático da Geração (CAG) e sobre um Sistema Pêndulo Invertido, que caracteriza bem uma planta instável. Os resultados comprovam a eficácia dos novos controladores. / Abstract: This work presents three new strategies of discrete-time control. The main focus of the work was given to the Sliding Mode Control (SMC) applied in systems that present delay in the processing of the control sign. The new control strategies provide laws of control of easy practical implementation and that at the same time are robust to uncertainties of the plant. A characteristic of these new approaches, for discrete-time control with delay-time, is the use of a Sliding Mode Control without the need of prediction of the control signal. The proposed design methods can be applied in the control of stable or unstable plants, with delay in the control signal. One of the strategies was elaborated to accomplish control just in discrete-time system without delay-time in the control sign, while the others are used for control in systems with delay-time. Simulations and experimental results are shown on a stable plant of Automatic Generation Control (AGC) and on Inverted Pendulum System, that is an unstable plant. The results prove the controllers' effectiveness. / Doutor