Orientador: José Paulo Fernandes Garcia / Banca: Haroldo Rodrigues de Azevedo / Banca: Marcelo Carvalho M. Teixeira / Resumo: Este trabalho apresenta uma nova estratégia de controle discreto. A técnica é baseada em Modos Deslizantes Discretos, utilizando uma lei de controle suave. Quando um algoritmo de controle é implementado em um computador digital, existe um atraso no tempo de computação, devido ao tempo de execução das instruções. Neste trabalho, vamos assumir que estes atrasos são constantes e menores que um período de amostragem. A presença do atraso no tempo de computação não apenas reduz a estabilidade e robustez, mas também degrada a performance de controle. O novo controlador proposto é projetado para atuar na presença destes atrasos, melhorando substancialmente o desempenho do controle. Outra propriedade importante deste controlador é a possibilidade de trabalhar com períodos de amostragem mais altos, garantindo o uso de freqüências mais baixas de processamento, ou seja, proporcionando uma economia do hardware de atuação. A nova lei de controle proposta foi aplicada na estabilização de quatro sistemas incertos e de natureza instável: Sistema Bola e Viga, Sistema Pêndulo Invertido Linear, Sistema Pêndulo Invertido Rotacional e Sistema Pêndulo Invertido Rotacional Duplo. Resultados das simulações são apresentados e comparados com resultados de outro controlador de Modo Deslizante, proposto na literatura, caracterizando um estudo comparativo, onde a eficácia do novo controlador projetado se mostra evidente, devido a seu algoritmo de fácil elaboração prática. Para melhor visualização do comportamento dos sistemas estudados e visando a contribuição no aprendizado de sistemas de controle, modelos de animação em três dimensões foram utilizados. / Abstract: This work presents a new strategy of discrete-time control. The technique is based on Discrete-Time Sliding Modes, using a smooth control law. When a control algorithm is implemented in a digital computer, there is a computation time delay, due the execution time of the instructions. In this work, we go to assume that these delays are constant and smaller than a sampling period. The presence of the computation time delay not only reduces the stability and robustness, but also degrades the control performance. The new considered controller is projected to work in the presence of these delays, improving substantially the performance of the control. Another important property of this controller is the possibility to work with higher sampling periods, guaranteeing the use of lower frequencies of processing, providing an economy of the actuation hardware. The new control law proposal was applied in the stabilization of four uncertain systems with unstable nature: Ball and Beam System, Linear Inverted Pendulum System, Rotational Inverted Pendulum System and Double Rotational Inverted Pendulum System. Simulations results are presented and compared with results of other Sliding Mode controller, proposed in the literature, characterizing a comparative study, where the effectiveness of the new designed controller shows evident, due your algorithm of easy practical elaboration. For better visualization of the behavior of the systems studied and aiming at the contribution in the learning of control systems, models of animation in three dimensions had been used. / Mestre

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-10Bitstream added on 2014-06-13T18:49:40Z : No. of bitstreams: 1 caun_ap_me_ilha.pdf: 919724 bytes, checksum: afeca633ca3cfd0780cb33c363186934 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta uma nova estratégia de controle discreto. A técnica é baseada em Modos Deslizantes Discretos, utilizando uma lei de controle suave. Quando um algoritmo de controle é implementado em um computador digital, existe um atraso no tempo de computação, devido ao tempo de execução das instruções. Neste trabalho, vamos assumir que estes atrasos são constantes e menores que um período de amostragem. A presença do atraso no tempo de computação não apenas reduz a estabilidade e robustez, mas também degrada a performance de controle. O novo controlador proposto é projetado para atuar na presença destes atrasos, melhorando substancialmente o desempenho do controle. Outra propriedade importante deste controlador é a possibilidade de trabalhar com períodos de amostragem mais altos, garantindo o uso de freqüências mais baixas de processamento, ou seja, proporcionando uma economia do hardware de atuação. A nova lei de controle proposta foi aplicada na estabilização de quatro sistemas incertos e de natureza instável: Sistema Bola e Viga, Sistema Pêndulo Invertido Linear, Sistema Pêndulo Invertido Rotacional e Sistema Pêndulo Invertido Rotacional Duplo. Resultados das simulações são apresentados e comparados com resultados de outro controlador de Modo Deslizante, proposto na literatura, caracterizando um estudo comparativo, onde a eficácia do novo controlador projetado se mostra evidente, devido a seu algoritmo de fácil elaboração prática. Para melhor visualização do comportamento dos sistemas estudados e visando a contribuição no aprendizado de sistemas de controle, modelos de animação em três dimensões foram utilizados. / This work presents a new strategy of discrete-time control. The technique is based on Discrete-Time Sliding Modes, using a smooth control law. When a control algorithm is implemented in a digital computer, there is a computation time delay, due the execution time of the instructions. In this work, we go to assume that these delays are constant and smaller than a sampling period. The presence of the computation time delay not only reduces the stability and robustness, but also degrades the control performance. The new considered controller is projected to work in the presence of these delays, improving substantially the performance of the control. Another important property of this controller is the possibility to work with higher sampling periods, guaranteeing the use of lower frequencies of processing, providing an economy of the actuation hardware. The new control law proposal was applied in the stabilization of four uncertain systems with unstable nature: Ball and Beam System, Linear Inverted Pendulum System, Rotational Inverted Pendulum System and Double Rotational Inverted Pendulum System. Simulations results are presented and compared with results of other Sliding Mode controller, proposed in the literature, characterizing a comparative study, where the effectiveness of the new designed controller shows evident, due your algorithm of easy practical elaboration. For better visualization of the behavior of the systems studied and aiming at the contribution in the learning of control systems, models of animation in three dimensions had been used.

The numerical solution of Stein (aka discrete Lyapunov) equations is the primary step in Newton's method for the solution of discrete-time algebraic Riccati equations (DARE). Here we present a low-rank Smith method as well as a low-rank alternating-direction-implicit-iteration to compute low-rank approximations to solutions of Stein equations arising in this context. Numerical results are given to verify the efficiency and accuracy of the proposed algorithms.

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The present doctoral thesis concentrate efforts in the consolidation of the benefits introduced by the plug-in repetitive action in the performance of pulse-width modulated voltage source inverters. The work is focused in the application of these inverters in double conversion uninterruptible power systems to comply the most demanding requirements of the international standards. The use of the plug-in repetitive action, in this application, is suitable because the inverter demands the advantageous characteristics of cyclic disturbance rejection by it introduced. In this scenario, this thesis is divided in two parts. The first one comprise the proposition of algorithms to solve some disadvantageous characteristics of the repetitive actions, such as the reduced stability margin and the unsuitable performance under reference signals with variable frequency. The second one, by the other hand, comprise the questions related to the design of these repetitive action controllers. It is included the proposition of a methodology that link the design of these controllers with the output filter of a double conversion UPS. Finally, it is worth to emphasize that are presented simulation and experimental results, obtained on a 1kVA laboratory prototype, that validate the proposes carried out. / A presente tese de doutorado concentra esforços na consolidação dos benefícios introduzidos pela ação de controle repetitiva auxiliar no desempenho de inversores de tensão modulados por largura de pulso. O trabalho está focado na aplicação destes inversores em fontes ininterruptas de energia (UPS) de dupla conversão, com o intuito de atender aos mais exigentes requisitos de desempenho das normas internacionais. A utilização da ação de controle repetitiva auxiliar, nesta aplicação, é adequada porque o inversor demanda as características vantajosas de rejeição de distúrbios cíclicos por ela introduzida. Neste contexto, esta tese se divide em duas partes. A primeira parte compreende na proposição de algoritmos para solucionar algumas das características desvantajosas dos controladores de ação repetitiva, tal como a reduzida margem de estabilidade e o desempenho não satisfatório para sinais de referências de freqüência variável. A segunda parte, por outro lado, trata das questões relacionadas ao projeto destes controladores de ação repetitiva, sendo proposta uma metodologia que integra o projeto destes controladores ao filtro de saída de uma UPS de dupla conversão. Por fim, destaca-se que são apresentados resultados de simulação e experimentais, obtidos em um protótipo de 1kVA, para validar as propostas deste trabalho.

The numerical solution of Stein (aka discrete Lyapunov) equations is the primary step in Newton's method for the solution of discrete-time algebraic Riccati equations (DARE). Here we present a low-rank Smith method as well as a low-rank alternating-direction-implicit-iteration to compute low-rank approximations to solutions of Stein equations arising in this context. Numerical results are given to verify the efficiency and accuracy of the proposed algorithms.

In this thesis, we consider the motion planning problem for an autonomous vehicle in an obstacle-cluttered environment approximated by zonotopes, and we propose an input sampling algorithm leveraging discrete-time control barrier function conditions (DCBF). Specifically, an optimization-based control barrier function that takes into account the geometric shapes of the vehicle and obstacles is constructed and verified. We then propose a discrete-time CBF that guarantees the safety during the inter-sampling intervals. It is worth noting that we do not need an explicit expression of the barrier function, but instead, an numerically efficient algorithm is proposed to evaluate and implement the CBF/DCBF conditions. Finally, an RRT algorithm is incorporated that draws the input sampling from the input space restricted to DCBF condition. Thanks to our proposed DCBF and input sampling method approach, our proposed method is less conservative, computationally efficient and guarantees the safety during the sampling intervals. Numerical simulation with unicycle model has been done to demonstrate the favorable properties of the algorithm. / I det här dokumentet tar vi upp problemet med rörelseplanering för ett autonomt fordon i en hinderfylld miljö som approximeras av zonotoper och föreslår en algoritm för insatsprovtagning som utnyttjar diskreta villkor för kontrollbarriärfunktioner (DCBF). Vi konstruerar och verifierar en optimeringsbaserad kontrollbarriärfunktion som tar hänsyn till fordonets och hindrens geometriska former. Vi föreslår sedan en diskret CBF i diskret tid som garanterar säkerheten under intervallerna mellan provtagningarna. Det är värt att notera att vi inte behöver ett explicit uttryck för barriärfunktionen, utan istället föreslås en numeriskt effektiv algoritm för att utvärdera och genomföra CBF/DCBF-villkoren. Slutligen införlivas en RRT-algoritm som drar inmatningsprovtagningen från inmatningsutrymmet som är begränsat till DCBF-villkoret. Tack vare vår föreslagna metod för DCBF och insatsprovtagning är vår föreslagna metod mindre konservativ, beräkningsmässigt effektiv och garanterar säkerheten under provtagningsintervallerna. Numerisk simulering med encykelmodell har gjorts för att verifiera algoritmen.

A repetitive control method for output voltage control of a three phase uninterruptible power supply (UPS) with isolation transformer is investigated. In the method voltage control loop is employed in the stationary dq frame. The controller eliminates the periodic errors on the output voltages due to inverter voltage nonlinearity and load disturbances. The controller design and implementation details are given. The controller is implemented on a 5-kVA UPS prototype which is constructed in laboratory. Linear and nonlinear loads for balanced and unbalanced load operating conditions are considered. The steady-state and dynamic performance of the control method are investigated in detail. The theory of the control strategy is verified by means of simulations and experiments.

The parallel active filter (PAF) is the modern solution for harmonic current mitigation and reactive power compensation of nonlinear loads. This thesis is dedicated to detailed analysis, design, control, and implementation of a PAF for a 3- phase 3-wire rectifier load. Specifically, the current regulator and switching ripple filter (SRF) are thoroughly investigated. A novel discrete time hysteresis current regulator with multi-rate current sampling and flexible PWM output, DHCR3, is proposed. DHCR3 exhibits a high bandwidth while limiting the maximum switching frequency for thermal stability and its implementation is simple. In addition to the development of DHCR3, in the thesis state of the art current regulation methods are considered and thoroughly compared with DHCR3. Since the current regulator type determines the SRF topology choice, various SRF topologies are considered and a thorough design study is conducted and SRF topology selection and parameter determination methods are presented via numerical examples. Through a PAF designed for a 10kW diode/thyristor rectifier load, the superior performance of DHCR3 is verified through simulations and experiments and via comparison to other current regulators. The sufficient switching ripple attenuation of the SRF structures for the designed PAF system and the overall performance of the designed and built PAF system are demonstrated via detailed computer simulations and laboratory experiments. This thesis aids the PAF current regulator and SRF selection, design, and implementation.

Series Active Filters (SAF) are designed for harmonic isolation and load voltage regulation of single-phase and three-phase voltage harmonic source type nonlinear loads. The novel Absolute Value Method (AVM) for load voltage harmonic extraction is proposed and applied in the control algorithm of SAF. The SAF compensated systems are represented by simplified linear models such that SAF controller gains can be easily determined. Harmonic isolation and load voltage regulation performances of 2.5 kW single-phase and 10 kW three-phase SAF compensated systems are evaluated by detailed simulations. Laboratory prototype single-phase and three-phase SAFs and loads are designed and manufactured. Digital signal processor based control platform is employed. Exclusive laboratory tests are conducted. Via laboratory experiments and simulations it is shown that AVM yields superior harmonic isolation and load voltage regulation performance compared to the conventional low/high pass filtering method. Theory, simulations, and experiments are well correlated and illustrate the feasibility of the proposed method.