As atividades sócio-econômicas vêm provocando alterações nocivas ao meio ambiente que atualmente assumem proporções mundiais. Graças à maciça utilização de combustíveis fósseis para a geração de energia e às crescentes práticas de desmatamento e queimadas das florestas, a concentração de dióxido de carbono (CO2) na atmosfera vem aumentando drasticamente. Como este gás é o principal responsável pelo efeito estufa, ele tem grande importância nos estudos e na mitigação do aquecimento global. Para justificar o seqüestro de carbono como um dos caminhos para ajudar na solução deste problema, muitos estudos vêm sendo realizados para avaliar os efeitos nas plantas de uma maior concentração desse gás. As câmaras de topo aberto (OTC, do inglês, open top chambers) são estruturas propícias para tais estudos, pois permitem o controle da concentração de CO2 interno sem que outros fatores climáticos como temperatura, umidade e luminosidade sejam demasiadamente alterados. Este trabalho teve como objetivo o desenvolvimento de um sistema para controlar o nível de CO2 no interior de uma OTC. Em termos de instrumentação eletrônica, foram instalados um sensor de CO2 e uma válvula proporcional, integrados a uma placa de aquisição de dados. Um modelo linear relacionando o CO2 na câmara ao sinal elétrico aplicado à válvula proporcional foi obtido aplicando-se técnicas de Identificação de Sistemas aos dados experimentais coletados com o processo operando em malha aberta. Este modelo foi utilizado no projeto de um controlador com compensação de tempo morto, baseado na estrutura de um preditor de Smith. O desempenho do sistema projetado foi analisado através de simulações, antes de implementá-lo na forma de um instrumento virtual. Os testes mostraram que o sistema manteve a concentração de CO2 na câmara próxima do valor de referência (720 ± 35 ppm) mesmo diante de distúrbios externos criados propositadamente durante os ensaios. / The harmful changes to the environment caused by socio-economic activities are now spread worldwide. Due to the massive use of fossil fuels for energy generation, to the increase in deforestation and forest burning, the carbon dioxide (CO2) concentration in the atmosphere has drastically increased. As this gas is the main responsible for the greenhouse effect, it has great importance for the studies and the mitigation of global warming. In order to justify carbon sequestration as an alternative to help solve this problem, many studies have been conducted to evaluate the effect of a greater concentration of this gas on plants. Open-top chambers (OTCs) are well suited for such studies, because they allow the control of the internal CO2 concentration without significantly modifying other environmental factors such as temperature, humidity and luminosity. This work aimed to develop a system to control the CO2 level inside an OTC. In terms of electronic instrumentation, a CO2 sensor and a proportional valve, integrated to a data acquisition board, were used. A linear model relating CO2 in the chamber to the electric signal applied to the proportional valve was obtained applying System Identification techniques to the experimental data collected from the process operating in open-loop mode. This model was used in the project of a controller with dead time compensation, based on the Smith Predictor structure. The performance of the projected system was analyzed through simulations, before implementing it in the form of a virtual instrument. The tests showed that the system kept the CO2 concentration of the chamber near the set-point (720 ± 35 ppm) even in the presence of external disturbances purposely created during the experiments.

Este trabalho apresenta todo um projeto de um sistema de supervisão e controle de um trocador de calor, desde os ensaios experimentais para a elaboração de um modelo matemático até a implementação do sistema de controle e supervisão em microcomputador. O sistema implementado consiste de um software didático e um sistema de aquisição de dados que irão realizar a supervisão e controle de um trocador de calor tipo casco e tubos. Neste software didático é possível implementar o controle PID e suas variações PI-D e I-PD além de permitir a implementação do sistema de controle adaptativo estrutura gain scheduling o qual muda os parâmetros de um controle PID de acordo com a mudança da dinâmica do trocador de calor. Como o trocador de calor apresenta um tempo morto em sua dinâmica, então optou-se por adicionar ao software didático um controle com algoritmo preditivo estrutura Preditor de Smith desta forma é possível realizar ensaios com e sem o algoritmo preditivo para uma comparação de resultados. Este sistema de supervisão e controle do trocador de calor poderá ser usado como ferramenta didática para alunos de diversos cursos, onde é possível realizar ensaios de diferentes estruturas de controle para posterior comparação e estudo de seus resultados. Resultados práticos de todas as estruturas de controle que o software implementa são apresentados e comparados neste trabalho. / This work presents thorough a supervision and control system project of a heat exchanger, from the experimental tests for the mathematical model rising to the control system implementation and supervision in a microcomputer. The implemented system consists of didactic software and a data acquisition system that will perform the supervision and control of a heat exchanger shell and tube type. In this didactic software it is possible to implement the PID control and its variations PI-D and I-PD besides allowing the implementation of the adaptive control system gain scheduling structure, which changes the PID control parameters according to the changes of the heat exchanger dynamics. As the heat exchanger presents dead time on its dynamics, it was opted to add to the didactic software a control with Smith Predictor structure predictive algorithm, thus it is possible to perform tests with and without the predictive algorithm for result comparison. This supervision and control system of the heat exchanger will be able to be used as a didactic tool for students from several courses, where it is possible to perform tests with different control structures to further comparison and study of its results. Pratical results of all the control structures that the software implements are presented and compared in this work.

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.

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.

Master thesis is focused on the philosophy of design adaptive controller. In the theoretic part are described parts of the adaptive controller, which belongs parts as online identification by recursive least-squares method and PSD controller, which can set its parameters according to identified system (use Z-N method). The part of control system with transport delay is situated at the conclusion of the theoretic part, there are focused on Smith predictor. Practical part is focused on verification of all algorithms, which was performed on models and real systems.

Master thesis is focused on the philosophy of design adaptive controller. In the theoretic part are described parts of the adaptive controller, which belongs parts as online identification by recursive least-squares method and PSD controller, which can set its parameters according to identified system (use Z-N method). The part of control system with transport delay is situated at the conclusion of the theoretic part, there are focused on Smith predictor. Practical part is focused on verification of all algorithms, which was performed on models and real systems.

Enhancing mineral processing techniques is a permanent challenge in the mineral and metal industry. Indeed to satisfy the requirements on the final product (metal) set by the consuming market, control is often applied on the mineral processing whose product, the ore concentrate, constitutes the input material of the extractive metallurgy. Therefore much attention is paid on mineral processing units and especially on concentration plants. As the ore size reduction procedure is the critical step of a concentrator, it turns out that controlling a grinding circuit is crucial since this stage accounts for almost 50 % of the total expenditure of the concentrator plant. Moreover, the product particle size from grinding stage influences the recovery rate of the valuable minerals as well as the volume of tailing discharge in the subsequent process.<p> The present thesis focuses on an industrial application, namely the Kolwezi concentrator (KZC) double closed-loop wet grinding circuit. As any industrial wet grinding process, this process offers complex and challenging control problems due to its configuration and to the requirements on the product characteristics. In particular, we are interested in the modelling of the process and in proposing a control strategy to maximize the product flow rate while meeting requirements on the product fineness and density.<p> A mathematical model of each component of the circuit is derived. Globally, the KZC grinding process is described by a dynamic nonlinear distributed parameter model. Within this model, we propose a mathematical description to exhibit the increase of the breakage efficiency in wet operating condition. In addition, a relationship is proposed to link the convection velocity to the feed ore rate for material transport within the mills.<p> All the individual models are identified from measurements taken under normal process operation or from data obtained through new specific experiments, notably using the G41 foaming as a tracer to determine material transport dynamics within the mills. This technique provides satisfactory results compared to previous studies.<p>Based on the modelling and the circuit configuration, both steady-state and dynamic simulators are developed. The simulation results are found to be in agreement with the experimental data. These simulation tools should allow operator training and they are used to analyse the system and to design the suitable control strategy.<p> As the KZC wet grinding process is a Multi-Input Multi-Output (MIMO) system, we propose a decentralized control scheme for its simplicity of implementation. To overcome all the control issues, a Double Internal Model Control (DIMC) scheme is proposed. This strategy is a feedforward-feedback structure based on the use of both a modified Disturbance Observer (DOB) and a Proportional-Integral Smith-Predictor (PI-SP). A duality between the DOB and PI-SP is demonstrated in design method. The latter is exploited to significantly simplify the design procedure. The designed decentralized controllers are validated in simulation on the process linearized model. A progressive implementation of the control strategy is proposed in the context of the KZC grinding circuit where instrumentation might not be obvious to acquire./<p><p> Améliorer les techniques de traitement de minerais est un défi permanent dans l'industrie des minéraux et des métaux. En effet, pour satisfaire aux exigences du produit fini (métal ) fixées par le marché de consommation, la commande automatique est souvent appliquée à l'usine du traitement de minerais dont le produit, le concentré, constitue la matière première de la métallurgie extractive. Une attention particulière est donc dévolue aux unités de traitement de minerais et en particulier aux concentrateurs. Comme le processus de réduction des dimensions granulométriques du minerai est l'étape critique d'un concentrateur, il s'avère que la commande d'un circuit de broyage est cruciale, car ce stade représente près de 50 % des dépenses totales de l' usine de concentration. De plus, la dimension granulométrique du produit de l'étape de broyage influe sur le taux de récupération des minéraux utiles ainsi que sur le volume des rejets du processus ultérieur.<p> La présente thèse porte sur une application industrielle, à savoir le concentrateur de Kolwezi (KZC qui est un circuit de broyage humide à double boucle fermée. Comme tout processus industriel de broyage humide, ce procédé présente une problématique de commande complexe et difficile en raison de sa configuration et des exigences relatives aux caractéristiques du produit. En particulier, nous nous intéressons à la modélisation de ce procédé et à proposer une stratégie adéquate de commande dans le but de maximiser le débit de production tout en respectant les exigences quant à la finesse et à la densité de la pulpe produite.<p> Un modèle mathématique de chaque composant du circuit a été déterminé. Globalement, le processus de broyage de KZC est décrit par un modèle dynamique non linéaire à paramètres distribués. Dans ce modèle, une description mathématique de l'augmentation de l'efficacité du broyage en milieu humide est proposée. En outre, nous avons proposé une relation liant la vitesse de convection au débit d'alimentation de minerais dans le modèle du transport de la matière à l'intérieur des broyeurs.<p> Tous les modèles mathématiques ont été identifiés à partir de mesures prises sur le procédé en fonctionnement d'équilibre stable ou à partir des données obtenues grâce à des nouvelles expériences spécifiques, notamment en utilisant le moussant G41 comme traceur pour déterminer la dynamique de transport de la matière dans les broyeurs. Cette technique a produit des résultats cohérents par rapport aux études antérieurs réalisées au moyen du traceur colorant ou radioactif.<p> Les simulateurs statique et dynamique ont été développés sur la base de la modélisation mathématique et de la configuration du circuit. Les résultats des simulations sont en accord avec les données expérimentales. Ces outils de simulation devraient permettre la formation des opérateurs et ont été utilisés pour analyser le système et concevoir la stratégie de commande la plus appropriée.<p> Comme le processus de broyage humide de KZC est un système à plusieurs grandeurs d'entrée et plusieurs grandeurs de sortie, nous avons proposé une structure de commande décentralisée en raison de sa simplicité de mise en œuvre .Afin de surmonter tous les problèmes de commande, un schéma de commande à double modèle interne (CDMI) est proposée. Cette stratégie est une structure à anticipation - rétroaction basée sur l'utilisation d'un observateur de perturbations (OBP) et d'un Prédicteur de Smith doté d'un régulateur Proportionnel-Intégral (PS-PI). Une dualité entre l'OBP et le PS-PI est démontrée dans la méthode de conception. Cette propriété est exploitée pour simplifier considérablement la procédure de conception. Les régulateurs décentralisés ainsi conçus sont validés en simulation sur le modèle linéarisé du procédé. Une mise en œuvre progressive de la stratégie de commande est proposée dans le contexte du circuit de broyage de KZC où l'instrumentation peut ne pas être évidente à acquérir.<p> <p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished