CAPES / Este trabalho apresenta a aplicação dos métodos de otimização por enxame de partículas e por colônia de formigas na otimização dos parâmetros de um controlador não linear de estrutura variável baseado em um controlador de variância mínima generalizada. Este controlador é composto por duas parcelas distintas: uma parcela linear e outra não linear. A parcela não linear do controlador apresenta dois parâmetros que afeta diretamente o comportamento do controlador e tais parâmetros são obtidos de maneira empírica. As metaheurísticas foram aplicadas para se obter os valores otimizados destes parâmetros. Foi considerada uma função custo que leva em consideração o erro de rastreamento e a variação da ação de controle. Um exemplo numérico do projeto deste controlador também é apresentado. O controlador otimizado foi experimentado em três plantas reais: controle de velocidade de um servomecanismo, controle de nível e controle de vazão em uma planta didática industrial. Os resultados obtidos enfatizam a melhora do desempenho do controlador com os parâmetros otimizados. Também é apresentada a comparação do desempenho deste controlador com um controlador PI. / This work presents the application of particle swarm optimization and ant colony optimization in the parameters optimization of a non-linear controller with variable structure based on generalized minimum variance control. This controller is composed of two parts: linear and non-linear. The non-linear term of the controller consists of two parameters that directly affects the control action, and are obtained by trial and error. Metaheuristic methods were applied to find out the optimized values of these parameters. The cost function used in metaheuristic methods takes account the error and the control signal. A numerical example of the design of this controller is also presented. Three practical experiments were considered: a servomechanism velocity control and two control loops in a didactic industrial plant, level and flow control. Experimental results emphasize the improvement of the system performance when the optimization methods are applied. A comparision with PI controller is shown.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Universidade Federal do Cearà / Atualmente, existem no mercado internacional vÃrios fabricantes de conversores estÃticos para infraestrutura fotovoltaica. No Brasil, por praticamente nÃo existir um produto com tecnologia nacional que atinja este nicho de mercado, à importante e urgente o desenvolvimento de tecnologia nacional na Ãrea de conversores para sistemas fotovoltaicos. O presente trabalho consiste no desenvolvimento de um conversor CC-CA trifÃsico com a finalidade de interligar um sistema fotovoltaico com a rede elÃtrica, onde o objetivo principal deste sistema à fornecer potÃncia ativa para o sistema elÃtrico trifÃsico. Este conversor CC-CA trifÃsico à composto por um estÃgio de conversÃo CC-CC, o qual consiste em um conversor do tipo elevador (Boost), e um estÃgio de conversÃo CC-CA. A escolha da topologia do conversor considerou alguns critÃrios, tais como baixo custo de aquisiÃÃo e de manutenÃÃo, baixa complexidade e elevado grau de compactaÃÃo e de confiabilidade. A modelagem e o controle do conversor sÃo feitos vetorialmente, ou seja, utilizando as transformadas dq0 direta e inversa. Este controle foi implementado em um controlador digital sinais (DSC) da famÃlia dsPIC. O projeto dos controladores de ambos os estÃgios foi feito de forma digital. Por meio da simulaÃÃo foi validado o funcionamento do conversor e de seus controladores projetados. Para a realizaÃÃo dos testes experimentais algumas modificaÃÃes de projeto tiveram que ser efetuadas, pois se verificou uma quantidade significativa de interferÃncia eletromagnÃtica e ruÃdos gerados pelo protÃtipo durante o seu funcionamento. Dentro das condiÃÃes estabelecidas foi possÃvel injetar na rede elÃtrica uma potÃncia em torno de 40% do valor mÃximo especificado. Os resultados experimentais obtidos a partir do protÃtipo montado em laboratÃrio validaram o algoritmo de controle implementado no conversor, sendo injetadas na rede elÃtrica correntes senoidais com baixo conteÃdo harmÃnico e na frequÃncia do sistema elÃtrico brasileiro. / Currently, there are several manufacturers in the international market of static converters for photovoltaic infrastructure. In Brazil, by there is no product with a national technology to reach this niche market, is important and urgent to develop national technology in the field of DC-AC converters to PV systems. The present work consists of developing of a three-phase AC-DC converter with the purpose of connect a PV system to the electricity grid, where the main objective of this system is to provide active power for the three-phase electrical system. This three-phase AC-DC converter is composed of a stage of DC-DC conversion, which consists in a boost converter, and a stage of DC-AC conversion. The choice of converter topology considered some criteria, such as low cost of acquisition and maintenance, low complexity, high compaction and reliability. The modeling and control of the converter are made using the concept of space vector, in the other words, using the dq0 transform direct and inverse. This control was performed in a digital signal controller (DSC) of dsPIC family. The design of the controllers of both stages was done digitally. Through simulation was validated the operation of the converter and its controllers designed. For the experimental tests some design changes had to be made because there was a significant amount of electromagnetic interference and noise generated by the prototype during its operation. From the conditions established was possible to inject into the electricity grid a just over 40% of the maximum value of power specified. The experimental results from the prototype validated the control algorithm implemented in the converter, being injected into the electricity grid sinusoidal currents with low harmonic content and frequency of the brazilian electrical system.

Orientador: Jose Raimundo de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T17:11:57Z (GMT). No. of bitstreams: 1 Campos_TatianeJesusde_D.pdf: 4875626 bytes, checksum: 36e6cf7484aa1c689c28b67404d977e5 (MD5) Previous issue date: 2007 / Resumo: Na última década os algoritmos evolutivos vem sendo aplicados na síntese e projeto de circuitos eletrônicos criando uma nova área de pesquisa denominada Hardware Evolutivo. Esta tese propõe o uso de Hardware Evolutivo como uma ferramenta para geração automática de circuitos aplicados ao controle de um pêndulo amortecido não linear. Inicialmente um amplo estudo sobre a utilização de computação evolutiva aplicada à síntese de circuitos eletrônicos foi realizado, de modo a identificar os principais benefícios, motivações, aplicações e desafios da área de Hardware Evolutivo. A seguir foi realizado um estudo de caso com o objetivo de realizar uma comparação experimental dos principais pontos que afetam o desempenho de um sistema de Hardware Evolutivo na evolução de circuitos digitais básicos. Após a realização destas etapas foi desenvolvido um Hardware Evolutivo para controle de um pêndulo não linear. O objetivo desta implementação foi apresentar comparações de desempenho entre diferentes abordagens para projetos de controladores. O uso do Hardware Evolutivo para obtenção do controlador tem como objetivo modelar o comportamento não linear do sistema e sintetizá-lo em um circuito digital combinacional criando assim uma alternativa de projeto automático para sistemas de controle. A análise e simulação do pêndulo não linear demonstra que a aplicação desta nova técnica de projeto de hardware apresenta resultados promissores / Abstract: In the last decade evolutionary algorithms application in electronic circuits synthesis have been intensively investigated, starting a new research area called Evolvable Hardware. This thesis considers the use of Evolvable Hardware as a tool for automatic design of circuits applied to the control of a nonlinear damped pendulum. Initially a study on the use of applied evolutionary algorithms to the synthesis of electronic circuits was carried out, in order to identify the main benefits, motivations, applications and challenges of the field of Evolvable Hardware. A case study was carried out with the objective to provide an experimental comparison of the main points that affect the performance of a system in the evolution of basic digital circuits. Finally a Evolvable Hardware controller unit for control a nonlinear damped pendulum was evolved. The objective of this implementation was to present performance comparisons between two different controllers designs. The analysis and simulation of nonlinear pendulum demonstrate that the application of this new technique of design provides excellent results / Doutorado / Engenharia de Computação / Doutor em Engenharia Elétrica

Iterative Learning Control (ILC) considers systems which perform the given desired trajectory repetitively. The command for the upcoming iteration is updated after every iteration based on the previous recorded error, aiming to converge to zero error in the real-world. Iterative Learning Control can be considered as an inverse problem, solving for the needed input that produces the desired output. However, digital control systems need to convert differential equations to digital form. For a majority of real world systems this introduces one or more zeros of the system z-transfer function outside the unit circle making the inverse system unstable. The resulting control input that produces zero error at the sample times following the desired trajectory is unstable, growing exponentially in magnitude each time step. The tracking error between time steps is also growing exponentially defeating the intended objective of zero tracking error. One way to address the instability in the inverse of non-minimum phase systems is to use basis functions. Besides addressing the unstable inverse issue, using basis functions also has several other advantages. First, it significantly reduces the computation burden in solving for the input command, as the number of basis functions chosen is usually much smaller than the number of time steps in one iteration. Second, it allows the designer to choose the frequency to cut off the learning process, which provides stability robustness to unmodelled high frequency dynamics eliminating the need to otherwise include a low-pass filter. In addition, choosing basis functions intelligently can lead to fast convergence of the learning process. All these benefits come at the expense of no longer asking for zero tracking error, but only aiming to correct the tracking error in the span of the chosen basis functions. Two kinds of matched basis functions are presented in this dissertation, frequency-response based basis functions and singular vector basis functions, respectively. In addition, basis functions are developed to directly capture the system transients that result from initial conditions and hence are not associated with forcing functions. The newly developed transient basis functions are particularly helpful in reducing the level of tracking error and constraining the magnitude of input control when the desired trajectory does not have a smooth start-up, corresponding to a smooth transition from the system state before the initial time, and the system state immediately after time zero on the desired trajectory. Another topic that has been investigated is the error accumulation in the unaddressed part of the output space, the part not covered by the span of the output basis functions, under different model conditions. It has been both proved mathematically and validated by numerical experiments that the error in the unaddressed space will remain constant when using an error-free model, and the unaddressed error will demonstrate a process of accumulation and finally converge to a constant level in the presence of model error. The same phenomenon is shown to apply when using unmatched basis functions. There will be unaddressed error accumulation even in the absence of model error, suggesting that matched basis functions should be used whenever possible. Another way to address the often unstable nature of the inverse of non-minimum phase systems is to use the in-house developed stable inverse theory Longman JiLLL, which can also be incorporated into other control algorithms including One-Step Ahead Control and Indirect Adaptive Control in addition to Iterative Learning Control. Using this stable inverse theory, One-Step Ahead Control has been generalized to apply to systems whose discrete-time inverses are unstable. The generalized one-step ahead control can be viewed as a Model Predictive Control that achieves zero tracking error with a control input bounded by the actuator constraints. In situations where one feels not confident about the system model, adaptive control can be applied to update the model parameters while achieving zero tracking error.

Digital control needs discrete time models, but conversion from continuous time, fed by a zero order hold, to discrete time introduces sampling zeros which are outside the unit circle, i.e. non-minimum phase (NMP) zeros, in the majority of the systems. Also, some systems are already NMP in continuous time. In both cases, the inverse problem to find the input required to maintain a desired output tracking, produces an unstable causal control action. The control action will grow exponentially every time step, and the error between time steps also grows exponentially. This prevents many control approaches from making use of inverse models. The problem statement for the existing stable inverse theorem is presented in this work, and it aims at finding a bounded nominal state-input trajectory by solving a two-point boundary value problem obtained by decomposing the internal dynamics of the system. This results in the causal part specified from the minus infinity time; and its non-causal part from the positive infinity time. By solving for the nominal bounded internal dynamics, the exact output tracking is achieved in the original finite time interval. The new stable inverses concepts presented and developed here address this instability problem in a different way based on the modified versions of problem states, and in a way that is more practical for implementation. The statements of how the different inverse problems are posed is presented, as well as the calculation and implementation. In order to produce zero tracking error at the addressed time steps, two modified statements are given as the initial delete and the skip step. The development presented here involves: (1) The detection of the signature of instability in both the nonhomogeneous difference equation and matrix form for finite time problems. (2) Create a new factorization of the system separating maximum part from minimum part in matrix form as analogous to transfer function format, and more generally, modeling the behavior of finite time zeros and poles. (3) Produce bounded stable inverse solutions evolving from the minimum Euclidean norm satisfying different optimization objective functions, to the solution having no projection on transient solutions terms excited by initial conditions. Iterative Learning Control (ILC) iterates with a real world control system repeatedly performing the same task. It adjusts the control action based on error history from the previous iteration, aiming to converge to zero tracking error. ILC has been widely used in various applications due to its high precision in trajectory tracking, e.g. semiconductor manufacturing sensors that repeatedly perform scanning maneuvers. Designing effective feedback controllers for non-minimum phase (NMP) systems can be challenging. Applying Iterative Learning Control (ILC) to NMP systems is particularly problematic. Incorporating the initial delete stable inverse thinkg into ILC, the control action obtained in the limit as the iterations tend to infinity, is a function of the tracking error produced by the command in the initial run. It is shown here that this dependence is very small, so that one can reasonably use any initial run. By picking an initial input that goes to zero approaching the final time step, the influence becomes particularly small. And by simply commanding zero in the first run, the resulting converged control minimizes the Euclidean norm of the underdetermined control history. Three main classes of ILC laws are examined, and it is shown that all ILC laws converge to the identical control history, as the converged result is not a function of the ILC law. All of these conclusions apply to ILC that aims to track a given finite time trajectory, and also apply to ILC that in addition aims to cancel the effect of a disturbance that repeats each run. Having these stable inverses opens up opportunities for many control design approaches. (1) ILC was the original motivation of the new stable inverses. Besides the scenario using the initial delete above, consider ILC to perform local learning in a trajectory, by using a quadratic cost control in general, but phasing into the skip step stable inverse for some portion of the trajectory that needs high precision tracking. (2) One step ahead control uses a model to compute the control action at the current time step to produce the output desired at the next time step. Before it can be useful, it must be phased in to honor actuator saturation limits, and being a true inverse it requires that the system have a stable inverse. One could generalize this to p-step ahead control, updating the control action every p steps instead of every one step. It determines how small p can be to give a stable implementation using skip step, and it can be quite small. So it only requires knowledge of future desired control for a few steps. (3) Note that the statement in (2) can be reformulated as Linear Model Predictive Control that updates every p steps instead of every step. This offers the ability to converge to zero tracking error at every time step of the skip step inverse, instead of the usual aim to converge to a quadratic cost solution. (4) Indirect discrete time adaptive control combines one step ahead control with the projection algorithm to perform real time identification updates. It has limited applications, because it requires a stable inverse.

Abstract not available

Content removed due to copyright Conference Proceedings I R. P. Fisk and S. M. Hasan, “Analysis of Internally-Generated Noise in Bandgap References,” in Proc. Electronics New Zealand Conf., Christchurch, New Zealand, Nov. 2006, pp. 18-23. Conference Proceedings II R. P. Fisk and S. M. Hasan, “Incremental Delta-Sigma Modulators for Temperature Sensing Applications,” in Proc. Int. Conf. Mechatronics and Machine Vision in Practice, Auckland, New Zealand, Dec. 2008, pp. 63-67. Conference Proceedings III R. P. Fisk and S. M. Hasan, “Low-Cost Temperature Sensor on a Modern Submicron CMOS Process,” in Proc. Electronics New Zealand Conf., Otago, New Zealand, 2009, pp. 43-48. / Digital control systems can be found performing a wide range of duties throughout modern society. These systems demand accurate, low cost interfaces to physical parameters of interest, one of the most common being temperature. A ‘smart’ sensor takes advantage of modern integrated circuit technology to create a sensor and analog-to-digital converter on the same silicon chip. Smart temperature sensors are widely available offering simple digital interfaces, high reliability, low power consumption and low cost. The primary weakness of these devices is the low inherent accuracy of on-chip thermal sensors. This thesis presents a smart thermal sensor design that improves upon current technology by employing a modern 0.13μm CMOS process and circuit-level techniques to reduce sensor size and power consumption while increasing digital converter resolution. Data is presented that shows uncalibrated sensor accuracy can be increased by using correlated device characteristics to compensate for random inter-device variation. The research findings guide the construction of future smart thermal sensors with uncalibrated accuracy levels exceeding that of any currently available design.

Este trabalho apresenta uma contribuição à área de controle de sistemas multivariáveis com a utilização de lógica fuzzy. Esta proposta consiste no desenvolvimento de um sistema de controle com duas entradas e duas saídas. São apresentados os principais aspectos estruturais e tecnológicos do sistema desenvolvido, assim como os fundamentos da estratégia de controle fuzzy, incluindo suas principais derivações, a saber, Fuzzy-PD, Fuzzy-Incremental, Fuzzy-PD+I. Ainda, foi considerada a utilização de uma topologia Fuzzy-P+I que se destaca pelo número reduzido de regras. Estratégias de controle descentralizado são consideradas. As estruturas de controle são implementadas no hardware CompactRIO R, em conjunto com o software de desenvolvimento LabVIEW R, com o objetivo de controlar nível e temperatura de fluido em um reservatório de uma planta didática. / This work presents a research proposal for the control of multivariable systems using fuzzy logic. This proposal consists in developing a control system with two inputs and two ouputs. It is presented the main structural and technological aspects of the developed system as well as the fundamentals of fuzzy control, including its main derivations, namely Fuzzy-PD, Fuzzy-Incremental, Fuzzy-PD+I. Still, it is considered the use of a fuzzy-P+I topology, which stands for the reduced number of rules. Fuzzy-P+I. Decentralized control strategies are considered. The control structures are implemented in the hardware CompactRIO R together with the LabVIEW R evelopment software, with the aim of controlling the fluid level and temperature in a tank of the didactic plant.

Thesis (MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2010 / Optimal control of fermentation processes is necessary for better behaviour of the process in order to achieve maximum production of product and biomass. The problem for optimal control is a very complex nonlinear, dynamic problem requiring long time for calculation Application of decomposition-coordinating methods for the solution of this type of problems simplifies the solution if it is implemented in a parallel way in a cluster of computers. Parallel computing can reduce tremendously the time of calculation through process of distribution and parallelization of the computation algorithm. These processes can be achieved in different ways using the characteristics of the problem for optimal control. Problem for optimal control of a fed-batch, batch and continuous fermentation processes for production of biomass and product are formulated. The problems are based on a criterion for maximum production of biomass at the end of the fermentation process for the fed-batch process, maximum production of metabolite at the end of the fermentation for the batch fermentation process and minimum time for achieving steady state fermentor behavior for the continuous process and on unstructured mass balance biological models incorporating in the kinetic coefficients, the physiochemical variables considered as control inputs. An augmented functional of Lagrange is applied and its decomposition in time domain is used with a new coordinating vector. Parallel computing in a Matlab cluster is used to solve the above optimal control problems. The calculations and tasks allocation to the cluster workers are based on a shared memory architecture. Real-time control implementation of calculation algorithms using a cluster of computers allows quick and simpler solutions to the optimal control problems.

CAPES / Este trabalho tem como objetivo a análise, projeto e implementação de estratégias de controle repetitivo para aplicação em sistemas de alimentação ininterrupta de energia (UPS - Uninterruptible Power Supply). Inicialmente, a revisão da literatura aborda os controladores mais aplicados neste propósito. Uma visão geral sobre sistemas UPS é realizada, com foco em diferentes topologias e o projeto de um filtro indutivo capacitivo (LC), para reduzir o conteúdo harmônico proveniente das comutações do inversor, é discutido. Na sequência, uma estratégia de controle é proposta. Nesta estratégia um termo feedforward é utilizado para gerar a forma de onda da tensão de saída e um controlador do tipo proporcional derivativo (PD) é inserido para compensar distúrbios não cíclicos. Para compensação de distúrbios cíclicos, algumas técnicas de controle repetitivo são analisadas e implementadas. A adição destes controladores apresenta bom desempenho, porém, quando o sistema sofre interferências, as características dinâmicas destes controladores são afetadas. Modificações são realizadas para tornar o sistema menos suscetível a ruídos de alta frequência e a distúrbios aperiódicos. Ainda, é proposto um controlador repetitivo com adaptação do ganho que apresenta robustez suficiente para boa regulação de tensão mesmo na presença de distúrbios aperiódicos e interferências eletromagnéticas. Por fim, é descrita a implementação de uma plataforma flexível, baseado em um inversor PWM controlado por um processador digital de sinais com periféricos para aquisição de dados e geração de PWM, DSC TMS320F28335. A partir desta plataforma, foram obtidos resultados experimentais para um protótipo de uma UPS monofásica, os quais comprovam o desempenho das técnicas de controle apresentadas e propostas. / This work presents an analysis, design and implementation of repetitive control strategies applied to uninterruptible power supplies (UPS) systems. At the beginning, a literature review of the main controllers concerning this purpose is shown. A global vision of UPS systems with focus on different topologies is made and the project of an inductive capacitive filter (LC) is presented where the goal is to reduce harmonic content due to the inverter switching. After that, a control strategy is presented. In this strategy a feed forward term is used to generate the wave form shape of the output voltage and a Proportional Derivative (PD) controller is introduced to compensate non cyclic disturbances. For the compensation of cyclic disturbs some repetitive control techniques are analyzed and implemented. The inclusion of these controllers provides a good performance for the output system, however, when the system is exposed to interferences, the dynamic characteristics of these controllers are affected. Modifications are presented to make the system less susceptible for high frequencies noise and aperiodic disturbs. In addition, a repetitive controller with gain adaptation is proposed with sufficient robustness to obtain a good voltage regulation even in the presence of aperiodic disturbances and electromagnetic interferences. Finally, the implementation of a flexible platform is presented, based on PWM inverter controlled by a digital signal processor with data acquisition and generation PWM peripherals, DSP TMS320F28335. From this platform, experimental results for a monophasic UPS prototype was obtained, which ones prove the performance of the control techniques presented and proposed.