This thesis focuses on the challenges that arise from the scheduling of heat exchanger network maintenance problems which undergo fouling and run continuously over time. The original contributions of the current research consist of the development of novel optimisation methodologies for the scheduling of cleaning actions in heat exchanger network problems, the application of the novel solution methodology developed to other general maintenance scheduling problems, the development of a stochastic programming formulation using this optimisation technique and its application to these scheduling problems with parametric uncertainty. The work presented in this thesis can be divided into three areas. To efficiently solve this non-convex heat exchanger network maintenance scheduling problem, new optimisation strategies are developed. The resulting contributions are outlined below. In the first area, a novel methodology is developed for the solution of the heat exchanger network maintenance scheduling problems, which is attributed towards a key discovery in which it is observed that these problems exhibit bang-bang behaviour. This indicates that when integrality on the binary decision variables is relaxed, the solution will tend to either the lower or the upper bound specified, obviating the need for integer programming solution techniques. Therefore, these problems are in ac- tuality optimal control problems. To suitably solve these problems, a feasible path sequential mixed integer optimal control approach is proposed. This methodology is coupled with a simple heuristic approach and applied to a range of heat exchanger network case studies from crude oil refinery preheat trains. The demonstrated meth- odology is shown to be robust, reliable and efficient. In the second area of this thesis, the aforementioned novel technique is applied to the scheduling of the regeneration of membranes in reverse osmosis networks which undergo fouling and are located in desalination plants. The results show that the developed solution methodology can be generalised to other maintenance scheduling problems with decaying performance characteristics. In the third and final area of this thesis, a stochastic programming version of the feasible path mixed integer optimal control problem technique is established. This is based upon a multiple scenario approach and is applied to two heat exchanger network case studies of varying size and complexity. Results show that this methodology runs automatically with ease without any failures in convergence. More importantly due to the significant impact on economics, it is vital that uncertainty in data is taken into account in the heat exchanger network maintenance scheduling problem, as well as other general maintenance scheduling problems when there is a level of uncertainty in parameter values.

In this thesis, we present some contributions to the Markov jump linear systems theory in a context of partial information on the Markov chain. We consider that the state of the Markov chain cannot be measured, but instead there is only an observed variable that could model an asynchronous phenomenon between the application and the plant, or a simple fault detection and isolation device. In this formulation, we investigate the problem of designing controllers and filters depending only on the observed variable in the context of H2, H?, and mixed H2/H? control theory. Numerical examples and academic applications are presented for active-fault tolerant control systems and networked control systems. / Nesta tese, apresentamos algumas contribuições para a teoria de sistemas lineares com saltos markovianos em um contexto de observação parcial da cadeia de Markov. Consideramos que o estado da cadeia de Markov não pode ser medido, porém existe uma variável observada que pode modelar um fenômeno assíncrono entre a aplicação e a planta, ou ainda um dispositivo de detecção de falhas simples. Através desse modelo, investigamos o problema da síntese de controladores e filtros que dependem somente da variável observada no contexto das teorias de controle H2, H?, e misto H2/H?. Exemplos numéricos e aplicações acadêmicas são apresentadas no âmbito dos sistemas de controle tolerantes a falhas e dos sistemas de controle através da rede.

Esta dissertação visa a modelagem, simulação e controle de um veículo aéreo não tripulado (VANT) do tipo quadricóptero, utilizando-se as técnicas de controle ótimo e controle robusto no espaço de estados. O quadricóptero deve realizar as funções de decolagem, voo em cruzeiro e pouso de maneira autônoma. A dissertação inclui a síntese e análise comparativa entre um observador de estados de ordem plena de Luenberger e um filtro de Kalman. Além disso, um controlador linear quadrático gaussiano e um controlador robusto serão sintetizados e avaliados, procurando-se avaliar qual tem o melhor desempenho nas diversas tarefas do VANT. / This dissertation includes the modeling, simulation and control of a quadrotor unmanned aerial vehicle by using optimum control and robust control techniques on the space state. The quadrotor must perform the takeoff, cruise flight and landing in an autonomous way. This report also presents the synthesis and comparative analysis between a Luenberger full order state observer and a Kalman filter. A linear quadratic gaussian controller and a robust controller will be also synthetized and analyzed, to compare which one exhibits the best performance on the UAV tasks.

Este trabalho apresenta uma proposta para o controle da suspensão veicular utilizando o amortecedor magneto-reológico, sendo o controle proposto composto pela associação de duas estratégias de controle, o controle ótimo e o controle fuzzy. O Controle ótimo é utilizado para determinar a força a ser utilizada pelo amortecedor magneto-reológico, e o controle fuzzy é utilizado para determinar a corrente elétrica, a ser utilizada no amortecedor magento-reológico e é obtido considerando o modelo de Mandani. Para o controle fuzzy, são consideradas duas entradas, a velocidade de deslocamento do pistão do amortecedor e a força prevista pelo controle ótimo, e uma saída, a corrente elétrica [A]. Para demonstrar a eficiência do controle proposto são consideradas simulações computacionais, utilizando um modelo matemático não-linear de um quarto de veículo. A análise do desempenho do controle é realizada, considerando excitações provocadas por irregularidades na pista, as irregularidades são representadas por entradas tipo degrau, impulso e senoidal. As simulações computacionais são realizadas, utilizando o Matlab® e o Simulink. Os resultados das simulações demonstram que o controle proposto aumenta a segurança do veículo e melhora sua dirigibilidade, reduzindo o deslocamento vertical do conjunto eixo e roda e o espaço de trabalho do amortecedor, quando comparado como o sistema passivo. Também contribui com o conforto dos passageiros, reduzindo as oscilações da carroceria, mantendo os níveis de aceleração abaixo dos considerados desconfortáveis pela norma BS 6841, 1987. Para verificar o comportamento do controle proposto, diante de incertezas, são realizadas simulações computacionais, considerando a possibilidade de erros paramétricos. As simulações, considerando os erros paramétricos, demonstram que o controle ótimo, mesmo quando sujeito a incertezas, permanece sendo estável e ótimo. / This work presents a proposal for control of vehicular suspension using the magneto-rheological damper, the proposed control is composed by association of two control strategy, the optimal control and the fuzzy control. The optimal control is used to determine the power to be applied by the magneto-rheological damper, and the fuzzy control is used to determine the electric current to be used in the magneto-rheological damper and is obtained considering the Mandani's model. For the fuzzy control two inputs are considered, the velocity of the piston's damper and the force provided by the optimal control, and one output, the electric current [A]. To demonstrate the efficiency of the proposed control, computational simulations are considered using a nonlinear mathematical model for a quarter-car. The performance of the control is analyzed considering excitements provoked by irregularities in the track, the irregularities are represented by entrances step type, pulse and sinusoidal. The computational simulations are performed using the Matlab® and the Simulink. The results of simulations show that the proposed control increases the vehicle security and improves the drive ability by reducing the vertical wheel displacement and the workspace to be used by the damper when compared to the passive system. It also helps with the comfort of passengers, reducing the bodywork oscillations, maintaining levels of accelerating below considered uncomfortable by standard BS 6841, 1987. To verify the behavior of the proposed control, in the face of uncertainty, computational simulations are carried out, considering the possibility of parametric errors. The simulations, show that the Optimal Control, even when subject to uncertainties, remains stable and optimal.

Esta dissertação tem por objetivo a implementação de um código para simular problemas hidrodinâmicos, bem como a possibilidade de controlar as elevações de onda resultantes numa determinada região por meio de uma vazão ótima controlada dentro do sistema estudado. O algoritmo implementado é baseado nas equações de águas rasas, as quais são aplicáveis em situações onde a altura d’água é de ordem muito menor do que as dimensões do sistema, que é discretizado espacial e temporalmente pelo Método dos Elementos Finitos e pelo método CBS (Characteristic Based-Split), respectivamente. O método de controle consiste na busca de uma curva de vazão de controle ótima que minimize a função objetivo, a qual compara os valores de altura d’água que se deseja encontrar em uma região especificada com os calculados pela simulação numérica. Para isso, utiliza-se um algoritmo evolutivo SCE-UA (Shuffled Complex Evolution – University of Arizona), que busca otimizar parâmetros de geração das curvas de vazão de controle, podendo estas serem modeladas por NURBS (Non- Uniform Rational B-Splines), que são capazes de encontrar a solução ótima, ou modeladas com curvas de forma triangular (linear) ou parabólica (quadrática) que apresentam uma solução aproximada de fácil implementação. Por fim, várias aplicações são realizadas, tanto para a simples simulação, quanto para o controle de problemas hidrodinâmicos, a fim de validar os algoritmos desenvolvidos e os resultados obtidos mostraram que os objetivos foram alcançados, encontrando uma forma eficiente de se fazer o controle de enchentes. / Implementation of a computational code for the numerical simulation of hydrodynamic problems as well as the ability to control the resulting wave elevations in a specific area, using an optimal flow controlled within the studied system are the aims of this work. The implemented algorithm is based on the shallow waters equations, which are applicable in situations where the water height is much smaller than the system dimensions, and are spatial and temporally discretized by the Finite Element Method and the CBS method (Caractheristic Based-Split), respectively. The control method consists in finding an optimal control flow curve that minimizes the objective function, which compares the objective value of water elevations in a specified region with those calculated by numerical simulation. An evolutionary algorithm called SCE-UA (Shuffled Complex Evolution - University of Arizona), which looks for optimize parameters of control flow curves generation, is used. These curves may be modeled by NURBS (Non-Uniform Rational B-Splines) which are able to find the optimal solution, or by curves of triangular (linear) or parabolic quadratic forms, which are an approximate solution easy to implement. Finally, several applications are performed for both simulation and control of hydrodynamic problems in order to validate the developed algorithms, and the results showed that the aims of this work were reached, finding an efficient way to control floods.

Dans le cadre du programme de croissance Européen 2020, la commission européenne a mis en place officiellement un chemin à long terme pour une économie à faible émission de carbone, en aspirant une réduction d’au moins 80% des émissions de gaz à effet de serre, d’ici 2050. Répondre à ces exigences ambitieuses, impliquera un changement majeur de paradigme, et notamment en ce qui concerne les infrastructures du réseau électrique. Les percées dans la technologie des semi-conducteurs et les avancées avec les nouvelles topologies d’électronique de puissance et leurs contrôle-commandes, ont contribué à l’impulsion donnée au processus en cours de réaliser un tel SuperGrid. Une percée technologique majeure a eu lieu en 2003, avec le convertisseur modulaire multi-niveaux (MMC ou M2C), présenté par le professeur Marquardt, et qui est actuellement la topologie d’électronique de puissance la plus adaptée pour les stations HVDC. Cependant, cette structure de conversion introduit également un certain nombre de défis relativement complexes tels que les courants “additionnels” qui circulent au sein du convertisseur, entrainant des pertes supplémentaires et un fonctionnement potentiellement instable. Ce projet de thèse vise à concevoir des stratégies de commande “de haut niveau” pour contrôler le MMC adaptées pour les applications à courant continue-haute tension (HVDC), dans des conditions de réseau AC équilibrés et déséquilibrés. La stratégie de commande optimale identifiée est déterminée via une approche pour la conception du type “de haut en bas”, inhérente aux stratégies d’optimisation, où la performance souhaitée du convertisseur MMC donne la stratégie de commande qui lui sera appliquée. Plus précisément, la méthodologie d’optimisation des multiplicateurs de Lagrange est utilisée pour calculer le signal minimal de référence du courant de circulation du MMC dans son repère naturel. / Following Europe’s 2020 growth program, the Energy Roadmap 2050 launched by the European Commission (EC) has officially set a long term path for a low-carbon economy, assuming a reduction of at least 80% of greenhouse gas emissions by the year 2050. Meeting such ambitious requirements will imply a major change in paradigm, including the electricity grid infrastructure as we know it.The breakthroughs in semi-conductor technology and the advances in power electronics topologies and control have added momentum to the on-going process of turning the SuperGrid into a reality. Perhaps the most recent breakthrough occurred in 2003, when Prof. Marquardt introduced the Modular Multilevel Converter (MMC or M2C) which is now the preferred power electronic topology that is starting to be used in VSC-HVDC stations. It does however, introduce a number of rather complex challenges such as “additional” circulating currents within the converter itself, causing extra losses and potentially unstable operation. In addition, the MMC will be required to properly balance the capacitive energy stored within its different arms, while transferring power between the AC and DC grids that it interfaces.The present Thesis project aimed to design adequate “high-level” MMC control strategies suited for HVDC applications, under balanced and unbalanced AC grid conditions. The resulting control strategy is derived with a “top-to-bottom” design approach, inherent to optimization strategies, where the desired performance of the MMC results in the control scheme that will be applied. More precisely, the Lagrange multipliers optimization methodology is used to calculate the minimal MMC circulating current reference signals in phase coordinates, capable of successfully regulating the capacitive arm energies of the converter, while reducing losses and voltage fluctuations, and effectively decoupling any power oscillations that would take place in the AC grid and preventing them from propagating into the DC grid.

Les fermes houlomotrices de seconde génération qui seront déployées dans les années qui viennent seront composées d’un grand nombre de modules identiques mouillés en mer et rapportant au rivage l’électricité produite par câbles sous-marins. Il a été montré que le contrôle des machines houlomotrices permet d’augmenter significativement leur rendement. Cependant, le contrôle optimal d’un système houlomoteur est non causal, i.e. son application nécessite la prévision de la force d’excitation soumise par le champ de vague sur chacun des éléments de la ferme. Les travaux présentés dans ce manuscrit ont consisté à mettre en place une stratégie de contrôle permettant une récupération d’énergie proche de l’optimum théorique en tenant compte des interactions hydrodynamiques liées à la configuration de ferme et permettant de résoudre la non-causalité d’un tel contrôleur en utilisant uniquement l’information contenue dans les vecteurs d’états des machines de la ferme. Dans un premier temps, les équations reliant les différents états des machines de la ferme ont été établies puis ont été utilisées afin d'effectuer une prévision des états sur les corps contrôlés permettant ainsi d’appliquer un contrôle réactif pseudo causal. Afin de contraindre la dynamique des corps et maitriser l’horizon de non causal du contrôleur, une méthode de fenêtrage a été appliquée à l’impédance du contrôleur. À l’aide d’un simulateur temporel développé spécifiquement, une étude de sensibilité a été conduite pour définir les paramètres optimaux et le comportement de la stratégie de contrôle et de son fenêtrage. La robustesse et la performance du contrôleur ont ensuite été évaluées pour différents changements extérieurs comme la dérive des corps, les variations d’orientation de houle, et l’étalement spectral directionnel. L’application de la stratégie de contrôle à une ferme de 10 corps a montré une récupération d’énergie supérieure à 83% de la limite théorique maximale. / The next generation of wave farms will becomposed of a large number of identical devices deployed offshore, which will transfer the retrieved energy to the shore using submarine cables. It hasbeen proven that the control of Wave Energy Converters can improve their efficiency. However, one of the main challenges of WEC control is the noncausality of the optimal controller. Indeed, the time domain application of this kind of control requires the forecast of the excitation force applied by the wavefield on each device of the farm. The work presented in this thesis aimed at developing and assessing a control strategy with an energy efficiency close to the theoretical optimum, taking into account the hydrodynamic interactions between the farm devices, and solving the non-causality issue using the measurements of the states of the device of the array. First, the equations linking the devices’ states within the array have been established and used to performa deterministic forecast of the states of the controlled bodies, which allowed to apply a pseudo-causal reactive control. Moreover, a window function hasbeen applied to the controller impedance in order to constrain the dynamic of the controlled bodies, and also to regulate the non-causal horizon of the controller. Then, using a time domain simulator developed specifically, a sensibility analysis has been performed to define the optimal parameters and the behavior of the controller with the window function.The robustness and the performances of the controller have also been assessed when affected by exterior changes such as device drift, wave orientation modification, and directional spreading of the wave spectrum. The collaborative controlled strategy applied to a farm of 10 devices has shown an energy efficiency over 83% of the theoretical bound.

L’objectif principal de ce travail est de développer une stratégie de gestion optimale afin d’améliorer l’efficacité énergétique des véhicules hybrides. Ces travaux comportent une partie analyse expérimentale de la mobilité, une partie modélisation numérique et une partie optimisation de la stratégie de gestion énergétique. L’étude de la mobilité a permis de mettre en avant et de quantifier la prédictibilité des trajets, dus à une forte mobilité contrainte. La modélisation dynamique du véhicule, nécessaire à l’étude de stratégie, a été réalisée par Représentation Energétique Macroscopique (REM) qui est une bonne méthode pour ce type d’étude. La stratégie proposée est basée sur le contrôle prédictif (MPC), résolu par une méthode de Programmation Quadratique, et mis en place en s’appuyant sur la prédiction de cycle issu de l’étude expérimentale. Les perspectives d’améliorations de ces travaux se situent au niveau de la consolidation de la base de données, et du niveau de modélisation de la batterie (impact de la thermique et du vieillissement) et du moteur thermique (prise en compte des polluants). / The main objective of this work is to develop an optimal management strategy to improve energetic efficiency of hybrid electric vehicle. This work is composed by a mobility experimental analysis part, a numerical modelization part and an optimization part of the energy management strategy. The study of mobility allow to highligth and quantify the predictibility of trips, due to a constraint mobility.The dynamic modelling of the vehicle which is necesary to study perfomance of strategies, was realized by Energetic Macroscopic Representation (EMR) which is a good methode in this case. The proposed strategy is based on the predictive control (MPC), solve by a method of Programming Quadratic, and set up resting on the cycle prediction determined from the experimental study. The perspectives of improvements of these work are consolidation of the database, and improvement of the battery modelling (imcluding thermal and ageing effects) and of the thermal engine (taken into account by some pollutants).

<p>This thesis concerns modeling and control of bilinear systems (BLS). BLS are linear but not jointly linear in state and control. In the first part of the thesis, a background to BLS and their applications to modeling and control is given. The second part, and likewise the principal theme of this thesis, is dedicated to theoretical aspects of identification, modeling and control of mainly BLS, but also linear systems. In the last part of the thesis, applications of bilinear and linear modeling and control to the activated sludge process (ASP) are given.</p>

Integrodifference equations are discrete in time and continuous in space, and are used to model the spread of populations that are growing in discrete generations, or at discrete times, and dispersing spatially. We investigate optimal harvesting strategies, in order to maximize the profit and minimize the cost of harvesting. Theoretical results on the existence, uniqueness and characterization, as well as numerical results of optimized harvesting rates are obtained. The order of how the three events, growth, dispersal and harvesting, are arranged also affects the harvesting behavior. Cholera remains a public health threat in many parts of the world and improved intervention strategies are needed. We investigate a key intervention strategy, vaccination, with optimal control applied to a cholera model. This system of differential equations has human compartments with susceptibles with different levels of immunity, symptomatic and asymptomatic infecteds, and two cholera vibrio compartments, hyperinfectious and non-hyperinfectious. The spread of the infection in the model is shown to be most sensitive to certain parameters, and the effect of varying these parameters on the optimal vaccination strategy is shown in numerical simulations. Our simulations also show the importance of the infection rate under various parameter cases.