Controle preditivo baseado em modelo (MPC) recebeu ampla aceitação na indústria química nos últimos 30 anos. O funcionamento básico dessa técnica é a utilização de um modelo para calcular o comportamento de uma planta em função das entradas que ela receberia nos próximos instantes. Define-se um objetivo, cuja principal contribuição é dada por uma medida da distância entre a condição predita da planta e um valor desejado previamente estipulado. Esse objetivo pode incluir ainda, por exemplo, penalizações sobre o esforço de controle necessário para levar a planta a uma condição mais próxima do desejável. São incorporadas restrições como limites físicos da planta e dos atuadores e formula-se um problema de otimização, buscando o ponto ótimo dessa função objetivo e respeitando as restrições. Neste trabalho é abordado o problema de controle preditivo baseado em modelo para sistemas que apresentem integradores e/ou tempos mortos. Estes elementos tornam mais difícil o controle de processos baseado apenas em técnicas clássicas. Apresenta-se aqui um modelo em espaço de estados que permite a representação dessas dinâmicas de modo suficientemente preciso. A formulação de modelo apresentada permite ainda a incorporação de informações sobre distúrbios medidos. É feita uma demonstração da estabilidade desse controlador quando o modelo por ele utilizado é idêntico ao comportamento real da planta. Numa aplicação real do controlador proposto, seria necessário estimar os estados da planta a partir das medidas das saídas. Em geral, utiliza-se um Filtro de Kalman para realizar esta tarefa. São estudados aqui os efeitos que a presença desse filtro teria sobre o desempenho do sistema em malha fechada. É proposto um observador baseado numa mudança heurística feita sobre o Filtro de Kalman e que permite, em certos casos, uma melhoria de desempenho. São apresentados os resultados de simulações de uma planta de óxido de etileno com o intuito de ilustrar a atuação do controlador estável desenvolvido e do observador proposto. / Model Predictive Control (MPC) has gained wide acceptance in chemical industry in the last 30 years. The basic principle of this technique is to use a model to calculate plants future behavior based on the inputs it would receive in the next sampling periods. It must be set an objective, mainly composed of some measure of the distance between plants predicted state and a previously specified condition. Objective value may also include, for example, penalty on control effort necessary to drive the plant closer to the desired state. It is possible to include constraints, such as physical limits of the plant or of the actuators and therefore to pose an optimization problem, searching the best value of the objective function that satisfies all constraints. This work addresses the problem of MPC applied to integrating systems and/or processes with dead-time. These kinds of plants are often difficult to control using only classical techniques. It is presented here a state space model to represent both cases accurately. Measured disturbances may also be incorporated to the model. Finally, it is shown that the proposed controller is stable when its internal model represents exactly plants dynamics. In any real application of this controller, it would be necessary to estimate plants states from outputs measures. In general, Kalman Filter solves this problem. It is studied in this work the effects caused by filters inclusion on closed loop performance. A new observer is proposed, based on a heuristic improvement over Kalman Filter which induces, for some systems, improved performance. Numerical simulation has been performed over a model of an ethylene oxide plant, illustrating the use of this stable controller and the proposed observer.

In the design of the state-of-the-art electronic products, power management circuits play a very important role for the enhancement of overall system efficiency. Switched mode DC-DC converter is an increasingly popular power management circuit due to its superior power conversion efficiency. This thesis introduces two efficiency optimization techniques for switched mode power electronic circuits. One is dead-time optimization. This technique can automatically adjust the dead-time on-the-fly according to the circuit operating conditions. Second, an energy conservation based high-efficiency dimmable multi-channel LED driver is discussed. An auxiliary power switched is use to allow free wheeling of the inductor current during the load disconnect period. The sequential burst mode PWM current sharing scheme with dimming capability can effectively reduce design complexity and cost. The proposed LED driver provides a practical solution for the realization of LED BLU in the flat panel TVs with local dimming capability according to the video content.

In the design of the state-of-the-art electronic products, power management circuits play a very important role for the enhancement of overall system efficiency. Switched mode DC-DC converter is an increasingly popular power management circuit due to its superior power conversion efficiency. This thesis introduces two efficiency optimization techniques for switched mode power electronic circuits. One is dead-time optimization. This technique can automatically adjust the dead-time on-the-fly according to the circuit operating conditions. Second, an energy conservation based high-efficiency dimmable multi-channel LED driver is discussed. An auxiliary power switched is use to allow free wheeling of the inductor current during the load disconnect period. The sequential burst mode PWM current sharing scheme with dimming capability can effectively reduce design complexity and cost. The proposed LED driver provides a practical solution for the realization of LED BLU in the flat panel TVs with local dimming capability according to the video content.

Controle preditivo baseado em modelo (MPC) recebeu ampla aceitação na indústria química nos últimos 30 anos. O funcionamento básico dessa técnica é a utilização de um modelo para calcular o comportamento de uma planta em função das entradas que ela receberia nos próximos instantes. Define-se um objetivo, cuja principal contribuição é dada por uma medida da distância entre a condição predita da planta e um valor desejado previamente estipulado. Esse objetivo pode incluir ainda, por exemplo, penalizações sobre o esforço de controle necessário para levar a planta a uma condição mais próxima do desejável. São incorporadas restrições como limites físicos da planta e dos atuadores e formula-se um problema de otimização, buscando o ponto ótimo dessa função objetivo e respeitando as restrições. Neste trabalho é abordado o problema de controle preditivo baseado em modelo para sistemas que apresentem integradores e/ou tempos mortos. Estes elementos tornam mais difícil o controle de processos baseado apenas em técnicas clássicas. Apresenta-se aqui um modelo em espaço de estados que permite a representação dessas dinâmicas de modo suficientemente preciso. A formulação de modelo apresentada permite ainda a incorporação de informações sobre distúrbios medidos. É feita uma demonstração da estabilidade desse controlador quando o modelo por ele utilizado é idêntico ao comportamento real da planta. Numa aplicação real do controlador proposto, seria necessário estimar os estados da planta a partir das medidas das saídas. Em geral, utiliza-se um Filtro de Kalman para realizar esta tarefa. São estudados aqui os efeitos que a presença desse filtro teria sobre o desempenho do sistema em malha fechada. É proposto um observador baseado numa mudança heurística feita sobre o Filtro de Kalman e que permite, em certos casos, uma melhoria de desempenho. São apresentados os resultados de simulações de uma planta de óxido de etileno com o intuito de ilustrar a atuação do controlador estável desenvolvido e do observador proposto. / Model Predictive Control (MPC) has gained wide acceptance in chemical industry in the last 30 years. The basic principle of this technique is to use a model to calculate plants future behavior based on the inputs it would receive in the next sampling periods. It must be set an objective, mainly composed of some measure of the distance between plants predicted state and a previously specified condition. Objective value may also include, for example, penalty on control effort necessary to drive the plant closer to the desired state. It is possible to include constraints, such as physical limits of the plant or of the actuators and therefore to pose an optimization problem, searching the best value of the objective function that satisfies all constraints. This work addresses the problem of MPC applied to integrating systems and/or processes with dead-time. These kinds of plants are often difficult to control using only classical techniques. It is presented here a state space model to represent both cases accurately. Measured disturbances may also be incorporated to the model. Finally, it is shown that the proposed controller is stable when its internal model represents exactly plants dynamics. In any real application of this controller, it would be necessary to estimate plants states from outputs measures. In general, Kalman Filter solves this problem. It is studied in this work the effects caused by filters inclusion on closed loop performance. A new observer is proposed, based on a heuristic improvement over Kalman Filter which induces, for some systems, improved performance. Numerical simulation has been performed over a model of an ethylene oxide plant, illustrating the use of this stable controller and the proposed observer.

The purpose of this thesis is to investigate different control strategies on a differential drive vehicle. The vehicle should be able to drive in turns at high speed and slowly when it should park next to a charger. In both these cases, good precision in both orientation and distance to the path is important. A PID and an LQ controller have been implemented for this purpose. The two controllers were first implemented in a simulation environment. After implementing the controllers on the system itself, tests to evaluate the controllers were made to imitate real-life situations. This includes tests regarding driving with different speeds in different turns, tests with load distributions, and tests with stopping accuracy. The existing controller on the system was also tested and compared to the new controllers. After evaluating the controllers, it was stated that the existing controller was the most robust. It was not affected much by the load distribution compared to the new controllers. However, the LQ controller was slightly better in most cases, even though it was highly affected by the load distribution. The PID controller performed best regarding stopping accuracy but was the least robust controller by the three. Since the existing controller has a similar performance as the LQ controller but is more robust, the existing controller was chosen as the best one.

No description available.

Motivated by the recent commercialization of gallium-nitride (GaN) switches, an effort was initiated to determine whether it was feasible to switch the flyback converter at 5 MHz in order to improve the power density of this versatile isolated topology. Soft switching techniques have to be utilized to eliminate the switching loss to maintain high efficiency at multi-megahertz. Compared to the traditional modeling of zero-voltage-switching quasi-square-wave converters, a numerical methodology of parameters design is proposed based on the steady-state model of zero-voltage switching quasi-square-wave flyback converter. The magnetizing inductance is selected to guarantee zero-voltage switching for the entire input and load range with the trade-off design for conduction loss and turn-off loss. A design methodology is introduced to select a minimum core volume for an inductor or coupled inductors experiencing appreciable core loss. The geometric constant Kgac = MLT/(Ac2WA) is shown to be a power function of the core volume Ve, where Ac is the effective core area, WA is the area of the winding window, and MLT is the mean length per turn for commercial toroidal, ER, and PQ cores, permitting the total loss to be expressed as a direct function of the core volume. The inductor is designed to meet specific loss or thermal constraints. An iterative procedure is described in which two- or three-dimensional proximity effects are first neglected and then subsequently incorporated via finite-element simulation. Interleaved and non-interleaved planar PCB winding structures were also evaluated to minimize leakage inductance, self-capacitance and winding loss. The analysis on the trade-off between magnetic size, frequency, loss and temperature indicated the potential for a higher density flyback converter. A small-signal equivalent circuit of QSW converter was proposed to design the control loop and to understand the small-signal behavior. By adding a simple damping resistor on the traditional small-signal CCM model, it can predict the pole splitting phenomenon observed in QSW converter. With the analytical expressions of the transfer functions of QSW converters, the impact of key parameters including magnetizing inductance, dead time, input voltage and output power on the small-signal behavior can be analyzed. The closed-loop bandwidth can be pushed much higher with this modified model, and the transient performance is significantly improved. With the traditional fix dead-time control, a large amount of loss during dead time occurred, especially for the eGaN FETs with high reverse voltage drop. An adaptive dead time control scheme was implemented with simple combinational logic circuitries to adjust the turn on time of the power switches. A variable deadtime control was proposed to further improve the performance of adaptive dead-time control with simplified sensing circuit, and the extra conduction loss caused by propagation delay in adaptive dead-time control can be minimized at multi-megahertz frequency. / Ph. D.

Current control is an important topic in modern power electronics system. For voltage source inverters, current control loop ensures the waveform quality at steady state and the fast response at transient state. To improve the current control performance, quite a few nonlinear control strategies have been presented and one well-known strategy is the hysteresis current control. It achieves fast response without stability issue and it has high control precision. However, for voltage source inverter applications, hysteresis current control has a wide switching frequency range, which introduces additional switching loss and impacts the design of harmonic filter. Other nonlinear current control strategies include one-cycle control, non-linear carrier control, peak current control, charge control, and so on. However, these control strategies are just suitable for specific topologies and it cannot be directly used by voltage source inverters. The recently proposed parabolic current control solves the frequency variation problem of hysteresis current control by employing a pair of parabolic carriers as the control band. By the use of parabolic current control, approximate-constant switching frequency can be achieved. Due to the cycle-by-cycle control structure, it inherently has fast response speed and high precision. These advantages make it suitable for voltage source inverters, including stand-alone inverters, grid connected inverters, active power filters, and power factor correction applications. However, parabolic current control has some limitations, such as dead-time effects, only working as bipolar PWM, complex hardware implementation, non-ideal converging speed. These problems are respectively solved in this dissertation and solutions include dead-time compensation, the implementation on dual-carrier unipolar PWM, sensorless parabolic current control, single-step current control. With the proposed dead-time compensation strategy, current control precision is improved and stable duty-cycle range are extended. Dual-carrier PWM implementation of parabolic current control has smaller harmonic filter size and lower power loss. Sensorless parabolic current control decreases the cost of system and enhances the noise immunity capability. Single-step current control pushes the convergence speed to one switching operation with simple implementation. High switching frequency is allowed and power density can be improved. Detailed analysis, motivation and experimental verification of all these innovations are covered in this dissertation. In addition, the duality phenomenon exists in electrical circuits, such as Thevenin's theorem and Norton's theorem, capacitance and inductance. These associated pairs are called duals. The dual of parabolic current control is derived and named parabolic voltage control. Parabolic voltage control solves the audible noise problem of burst mode power converters and maintains high efficiency in the designed boost converter. / Ph. D.

La commande sans capteur mécanique de la machine synchrone à aimants permanents est un sujet largement répandu dont les plus grandes difficultés connues, quel que soit l’observateur utilisé, sont celui du démarrage à vitesse nulle et plus largement de la commande aux basses vitesses, et celui du rejet des fortes perturbations du couple. Afin d’y faire obstacle, diverses adaptations des algorithmes d’observateur ont été proposées afin d’améliorer le comportement de la machine en commande sans capteur. Par ailleurs, il est couramment admis que les déchets de tension produit par l’onduleur sont nuisibles à l’observation de la position, les tensions de référence étant légèrement différentes des tensions appliquées aux enroulements de la machine. Quelques propositions apparaissent dans certaines publications notamment en établissant un algorithme de compensation. C’est ainsi que les travaux de cette thèse portent sur cette thématique, celle d’améliorer la commande sans capteur dans les situations d’observabilité difficile en proposant une solution originale afin de faire correspondre au mieux les tensions appliquées à la machine et les tensions de référence utiles à l’observateur. Les résultats montrent que la solution proposée et largement analysée améliore considérablement le comportement de la machine en commande aux basses vitesses et en rejet de perturbation, tant en régime permanent qu’en régime transitoire ; une analyse de Fourier des courants mesurés atteste l’efficacité de la méthode et une analyse des grandeurs observées par la statistique descriptive met en lumière l’intérêt de l’algorithme. Nous montrons ainsi que la solution proposée permet d’observer la vitesse et la position en deçà de la vitesse mécanique de 15 rad/s alors que la commande est instable en deçà de 20 rad/s quand la solution n’est pas mise en œuvre. Un constat similaire apparaît en rejet de perturbation. D’autres résultats montrent que l’observation à plus basse vitesse est entachée d’une perturbation liée à un couple pulsatoire dont l’origine peut être le couple de détente, lequel n’est pas pris en compte par le modèle de la machine. / The sensorless control of the permanent magnet synchronous machine is a subject widely spread. Two great difficulties are known; (i) the start at nil initial speed and more generally the control at very low speed whatever the observer used and (ii) the high torque disturbance rejection. In order to hinder these difficulties numerous modifications of observer algorithms were proposed to improve the performances of the permanent magnet synchronous machine sensorless control. Moreover, we admit commonly that the drop voltages due to the inverter are prejudicial to the position estimated, because the difference between the voltage reference transmitted to the PWM (pulse width modulation) and the motor winding voltage is not negligible at low speed and low load torque. According to the literature, several papers propose some solutions by compensation algorithms and voltage estimator in particular. So, the goal of this thesis is to estimate the winding voltage and to apply the state observer by Extended Kalman Filtering to improve more finely the sensorless control. We propose an original solution to estimate the voltage references which is applied to the observer. Numerous experimental results show the attractive effects in marked contrast to the sensorless control results without estimation of the winding voltages. The results of sensorless control show that the solution proposed which widely analysed improves significantly the estimation errors of the motor running in low speed range and low torque disturbances range. Fourier analyses and statistic data obtained in steady state speed and results during the transient response indicate complementary results and highlight the interest of the estimation algorithm. Our study brings out that the estimation error reduction allows to running the motor at mechanical speed short of 15 rad/s. In the other hand, the system is instable with speed short of 20 rad/s if the voltage references are used by the observer rather than the estimation voltages. The same improvement appears in disturbance rejection. Other results show that the estimated position errors at lower speed increases in spite of the estimation algorithm. In fact, the torque disturbances are dominant at low speed, low load torque and are harmful to control the electromagnetic torque.

Este trabalho descreve o desenvolvimento de um sistema de controle com compensação de tempo morto aplicado a um ventilador para simular os efeitos do vento em modelos de embarcações. O sistema é instalado no tanque de provas do Departamento de Engenharia Naval da Escola Politécnica da USP. Um sistema de controle baseado em computador é elaborado para a realização dos testes e validação, procedendo-se inicialmente a identificação do sistema a ser controlado. Na malha de controle, o sinal de referência é a velocidade do vento desejada em uma distância pré-definida do ventilador e pode ser tanto um valor constante (representando um vento constante) ou um valor variante no tempo (representando uma rajada de vento). O sistema atuador consiste de um inversor de frequência que aciona o ventilador e a velocidade do vento é medida por um anemômetro, cujo sinal é usado como realimentação para o controlador. A sintonia da malha é realizada pelo método do modelo interno (IMC) e o efeito do tempo morto é observado nos testes, aplicando-se o compensador baseado no Preditor de Smith para minimizá-lo. Pelos resultados dos ensaios, conclui-se que o Preditor de Smith melhora o desempenho do sistema de geração de vento. / This paper describes the development of a control system with dead time compensation applied to a fan to simulate wind effects in models of vessels. The system is installed on the academic towing tank of the Naval Architecture and Oceanic Engineering Department of the University of São Paulo. A control system based on computer is designed for testing and validation, proceeding initially to identify the system to be controlled. In the control loop, the set-point is the desired speed of the wind on a pre-defined distance from the fan and it can be either a constant value (representing a constant wind) or a time-varying value (representing a wind gust). The actuator system consists of a frequency-inverter that drives the fan and the wind speed is measured by an anemometer, whose signal is used as feedback to the controller. The tuning of the controller is made by the internal model control (IMC) and the effect of dead time is observed in the tests, applying the compensator based on Smith Predictor to minimize it. Through the results from the tests, it was concluded that the Smith Predictor improves the performance of the wind generation system.