Many control systems of practical importance are multivariable. In such systems, each manipulated variable (input signal) may affect several controlled variables (output signals) causing interaction between the input/output loops. For this reason, control of multivariable systems is typically much more difficult compared to the single-input single-output case. It is therefore of great importance to quantify the degree of interaction so that proper input/output pairings that minimize the impact of the interaction can be formed. For this, dedicated interaction measures can be used. The first part of this thesis treats interaction measures. The commonly used Relative Gain Array (RGA) is compared with the Gramian-based interaction measures the Hankel Interaction Index Array (HIIA) and the Participation Matrix (PM) which consider controllability and observability to quantify the impact each input signal has on each output signal. A similar measure based on the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cmathcal%20H_2" /> norm is also investigated. Further, bounds on the uncertainty of the HIIA and the PM in case of uncertain models are derived. It is also shown how the link between the PM and the Nyquist diagram can be utilized to numerically calculate such bounds. Input/output pairing strategies based on linear quadratic Gaussian (LQG) control are also suggested. The key idea is to design single-input single-output LQG controllers for each input/output pair and thereafter form closed-loop multivariable systems for each control configuration of interest. The performances of these are compared in terms of output variance. In the second part of the thesis, the activated sludge process, commonly found in the biological wastewater treatment step for nitrogen removal, is considered. Multivariable interactions present in this type of bioreactor are analysed with the tools discussed in the first part of the thesis. Furthermore, cost-efficient operation of the activated sludge process is investigated.

Hydraulic systems are widely applied in industry for position or force control. However, due to hydraulic system nonlinearities, it is difficult to achieve a precise model valid over a large range of frequencies and movements. The work in this dissertation focuses on a high performance hydraulic test bench which involves three main hydraulic components, i.e. two high performance servovalves, a double rod actuator, and a specific intermediate block connecting the servovalves and actuator. This rig has been designed for testing aerospace or automotive components in real conditions (e.g. wear and ageing effects). The main objectives of this dissertation are first the development of a virtual prototype based on a precise model which is derived from the physical principles and experimental works, and then second the synthesis of several nonlinear control laws of this actuation system in a large operating range with a good robustness to the perturbations. The proposed model based on Bond Graph shows a very good agreement with experimental results not only at low frequencies, but also at high frequencies. Moreover, its performances are improved at high frequencies by introducing the dynamic effects due to the intermediate block. Besides, multivariable and monovariable control strategies, based on respectively the backstepping and the model-free method, are developed and implemented on the test bench. All the control strategies proposed have been validated by simulations and experiments. Results show they lead to better tracking precision and robustness performance compared to the conventional control techniques.

Utilização de experimentos com relés para identificação de pontos da resposta em freqüência de sistemas multivariáveis quadrados e sintonia de controladores PID descentralizados. / It use relay experiments for square multivariable system frequency response and decentralized PID controller tunning.

Utilização de experimentos com relés para identificação de pontos da resposta em freqüência de sistemas multivariáveis quadrados e sintonia de controladores PID descentralizados. / It use relay experiments for square multivariable system frequency response and decentralized PID controller tunning.

Le travail de cette thèse s'inscrit dans le cadre du développement de la méthodologie CRONE (Commande Robuste d'Ordre Non Entier) multivariable. Il porte plus précisément sur la simplification de sa mise en oeuvre pour la synthèse de régulateurs multivariables robustes, avec une application au contrôle de bancs d'essais moteur haute dynamique, notamment ceux développés par l'entreprise D2T. Le premier chapitre présente les différents types de bancs d'essais, leur fonctionnement et leur problématique. Le deuxième chapitre présente tout d'abord une modélisation physique simple des bancs d'essais qui en permet ensuite leur simulation, puis est dédié à leur identification fréquentielle avec une application à un banc d'essais équipé d'un moteur Diesel. Le troisième chapitre présente la méthodologie CRONE multivariable et différents développements permettant d'en simplifier la mise en oeuvre notamment grâce à l'optimisation d'un nouveau paramètre. Illustrant ces développements, la boite à outils CRONE multivariable qui a été développée est alors utilisée pour la synthèse de la loi de commande d'une maquette de banc d'essais constituée de deux moteurs asynchrones. Finalement, le quatrième chapitre est dédié à la validation des développements présentés par leur application à un banc d'essais haute dynamique équipé d'un moteur Essence. Ce chapitre présente également les différents outils logiciel développés pour faciliter l'intégration de la méthodologie CRONE full MIMO aux produits D2T. / The work presented in this Thesis is part of the CRONE (robust control with fractional integration order) multivariable methodology development. It deals with the simplification of the robust multivariable control system implementation with application to the control of high dynamic engine test-benches, including those developed by the D2T company. The first chapter introduces different kind of test-benches and gives a general idea about how those systems work while explaining their problems. While the first part of chapter II presents a simple method for test-benches modeling which then allows their simulation, the second part is dedicated to their frequency-domain system identification. The defined identification procedure is applied to a test-bench equipped with a Diesel engine. The third chapter presents the CRONE multivariable methodology and different developments to simplify its use. Reflecting these developments, the developed CRONE multivariable toolbox is used to design a control system for a test-bench consists of two asynchronous motors. The fourth chapter is dedicated to validate the presented work by applying these developments to a high dynamic test-bench with a spark ignition engine. This chapter presents the various software tools developed to simplify the implementation to D2T products of the CRONE full MIMO methodology.

O presente trabalho apresenta a descrição de um modelo matemático completo em seis graus de liberdade para um Veículo Submersível Autônomo (VSA) sub-atuado. Desenvolveram-se métodos de identificação de sistemas para identificar o modelo não linear do veículo. A fim de evitar problemas de divergência na estimação de parâmetros hidrodinâmicos do modelo, usou-se o método de transformação paramétrica. Usou-se o filtro estendido de Kalman como estratégia para o processo de estimação de parâmetros quando ruídos de natureza gaussiana estavam presentes no modelo e nas medidas. Com o objetivo de estimar um maior número de parâmetros de uma só vez, empregou-se o método de máxima verossimilhança. Os experimentos mostraram que o filtro de Kalman responde bem à estimação de parâmetros específicos, porém, divergiu facilmente à estimação de múltiplos parâmetros. Uma alternativa que apresentou melhor desempenho foi o método de máxima verossimilhança. Testaram-se manobras circulares e de zig-zags para a obtenção de dados do veículo. Para os ensaios experimentais, utilizou-se o VSA sub-atuado do Laboratório de Veículos Não Tripulados (LVNT) do Departamento de Engenharia Mecatrônica da Escola Politécnica da Universidade de São Paulo. Validou-se o modelo identificado mediante o simulador do veículo. Numa segunda etapa, desenvolveram-se controladores H¥ capazes de controlar a dinâmica do VSA em seus seis graus de liberdade. Projetaram-se controladores SISO (uma entrada e uma saída) e MIMO (múltiplas entradas e múltiplas saídas) com o fim de avaliar o acoplamento dinâmico do sistema. Projetaram-se controladores centralizados robustos para garantir as condições de operação num ambiente marinho e em condições de laboratório próximas às de uma aplicação real. As leis de controle são baseadas na técnica de sensibilidade mista H¥ que garantem condições de robustez do sistema de controle, tanto no desempenho quanto na estabilidade. Uma estrutura de controle de dois graus de liberdade (2GL) produziu melhores propriedades de desempenho comparada com a estrutura do controlador de um grau de liberdade. Compararam-se as respostas dos controladores descentralizados SISO e os controladores centralizados. O controlador 2GL garantiu as especificações do projeto, inclusive aquelas definidas no domínio do tempo. Um controlador central pode controlar o veículo na realização de manobras complexas em três dimensões que emulem a inspeção ou monitoramento de sistemas offshores ou outras tarefas comuns na exploração submarinha. O trabalho apresenta também a integração dos algoritmos de controle com o sistema de tempo real embarcado, os sensores inerciais de navegação, os motores elétricos para os atuadores lemes e o propulsor, o banco de baterias e o processador central ARM7 de 32 bits de ponto fixo. Traduziram-se os algoritmos de controle de ordem elevada para a aritmética de ponto fixo produzindo a execução rápida e, no possível, evitando a ocorrência de transbordamento de dados. / This work presents a full six degrees-of-freedom mathematical model description of a subactuated Autonomous Underwater Vehicle (AUV). The work developed methods of System Identification for identifying the nonlinear model of the vehicle. In order to avoid divergence problems in the process of hydrodynamic, it used the parametric transformation technique. It used the extended Kalman filter to estimate the model parameters subject to Gaussian noise, in the process and in the measurements. In order to tackle the problem of multiple parameter estimation at once, the work used the maximum likelihood approach. The experimental results showed that the Kalman filter approach is better when the aim is to estimate a specific parameter, however, it diverges easily when the aim is to estimate multiple parameters. The maximum likelihood technique showed better response to estimate multiple parameters of the model. Zig-zag and circular standard maneuvers were tested with the identification algorithms. For experimental tests, an AUV, namely Pirajuba and constructed by the Unmanned Vehicle Laboratory (LVNT), were used. Results were also assessed using an AUV six degrees of freedom simulator. In a second stage, the work developed H¥ controllers to manoeuvre the vehicle in six-degrees-of-freedom. Decoupled SISO (single input and single output variables) and MIMO (multiple input and multiple output variables) controllers were synthesized in order to validate the coupling dynamics of the AUV. Moreover, centralized robust controllers were developed to control the vehicle in the sea and in test tanks with extreme conditions close to the ocean environmental. The control techniques were based in the H¥ mixed sensitivity approach which guarantees robust performance and stability of the sub-actuated system. A structure of two-degrees-of-freedom (2GL) controller presented better performance compared with the classic single H¥ controller of one degree of freedom structure. A comparison between responses was used to validate the decoupling and centralized controllers. The 2GL controller has good performance specifications despite these defined in the time domain. A central controller can control the AUV in complex maritime task that require complex and three-dimensional manoeuvres. The work deals also with the implementation issues coding these advanced control algorithms into the real time embedded system including inertial sensors, electric motors for the propeller and actuator surfaces, battery banks, and the unit central process ARM7 of 32 bits of fixed point. The control algorithms were translated from floating point to fixed point arithmetic avoiding data overflow, seeking simplicity and fast task execution.

Este trabalho apresenta o controle de posição e orientação de um modelo não linear de Plataforma de Stewart com seis graus de liberdade construído no ambiente de sistemas multicorpos ADAMS® desenvolvido pela Mechanical Dynamics, Inc. O modelo não linear é exportado para o ambiente SIMULINK® desenvolvido pela MathWorks, Inc., onde o controle de posição e orientação é realizado a partir da linearização do modelo e a aplicação de um sistema seguidor com realimentação de estados. Utililiza-se, também o SIMULINK® para implementar a dinâmica de um sistema servoválvula e cilindro hidráulico com um servocontrole de pressão e assim simular o comportamento dinâmico de um simulador de vôo com acionamento hidráulico. A utilização destes pacotes comerciais visa obter uma economia de tempo e esforço na modelagem de sistemas mecânicos complexos e na programação para obtenção da resposta do sistema no tempo, além de facilitar a análise de várias configurações de Plataformas de Stewart / This work shows the position and orientation control of a non-linear model of a Stewart platform with six degree of freedom developed in the multibody systems environment ADAMS® (Mechanical Dynamics, Inc.). The non-linear model is exported to SIMULINK® (MathWorks, Inc.), where the position and orientation control is accomplished using the linear model and applied as a tracking-system with state-feedback. The SIMULINK® is also used to implement the dinamics of the servovalve and hydraulic cylinder with pressure-control servo and so simulate the dynamic behavior of the flight simulator with hydraulic drive. These commercial packages are used seeking to save time and effort in the modeling of complex mechanical systems and in the programming to get the time response of the system, facilitating the analysis of several Stewart Platforms configurations.

Utilização de experimentos com relés para identificação de pontos da resposta em freqüência de sistemas multivariáveis quadrados e sintonia de controladores PID descentralizados. / It use relay experiments for square multivariable system frequency response and decentralized PID controller tunning.

L'objectif de cette thèse est la conception, dans un premier temps, des différentes stratégies de commande pour un générateur hybride composé par une pile à combustible et une source auxiliaire de stockage d'énergie. L'outil des Inégalités Linéaires Matricielles (LMI) est utilisé dans la thèse pour la solution du problème de la commande robuste et multi-variables. Dans un premier temps la commande se consacre à la gestion de la partie électrique de la pile. Des stratégies de commande sont proposées pour les convertisseurs élévateurs du bus continu mais aussi pour le contrôle d'un onduleur de tension conçu pour une opération en mode isolé du réseau. La validation d'une partie du contrôle sous un banc d'essai a été réalisée. Dans un deuxième temps, la commande de la partie fluidique de la pile a été traitée. La gestion de la dynamique de l'air en entrée de la pile est assurée par la commande du débit du compresseur. Le sous-système de compression d'air est régulé pour garantir un certain taux d'excès d'oxygène désiré, ce qui permet d'améliorer les performances de la pile. Une introduction au contrôle des systèmes à paramètres variants (LPV) est aussi présentée. Des études de robustesse des contrôleurs proposés ont été effectuées, et ces caractères robustes sont comparés avec plusieurs méthodes de commande classique, prouvant ainsi l'importance des méthodologies de commande robuste et multi-variables. / The objective of this thesis is the design of several control strategies for a hybrid power generator composed by a fuel cell and an auxiliary energy storage source. The Linear Matrix Inequalities (LMI) tools are extensively used in this dissertation as a solution to the mutivariable robust control problem. As a first approach, the control methodology is consecrated to the electrical power management sub-system of the fuel cell. Different strategies are proposed to control the hybrid boost power converter configuration for DC voltage applications. The methodology is extended to AC islanded applications considering the additional control of a voltage inverter. The validation on a dedicated test-bench, of a part of the proposed control strategies, is presented. In a second approach, the control of the air supply system is addressed. The management of the air dynamic entering the fuel cell is assured by the control of the air flow of a compressor. The air supply sub-system is controlled to keep a desired oxygen excess ratio, this allow to improve the fuel cell performance. An introduction to the control of Linear Varying Parameter (LPV) systems is also presented. Robustness analysis studies are performed, these robust properties are contrasted with several classic control strategies, demonstrating the advantage and the importance of multivariable robust methodologies.

No / A multivariable model of an automotive gas turbine, obtained from the linearized system equations is investigated. To facilitate vehicle speed changes, whilst protecting the system against thermal damage, control of the power turbine inlet gas temperature and gas generator speed is proposed by feedback regulation. Fuel flow and the power turbine nozzle area variations are the selected, manipulatable inputs. Owing to the limited control energy available for regulation purposes a multivariable, optimum, minimum control effort strategy is employed in the inner loop controller design study. Simulated, open and closed loop system responses are presented for purposes of comparison. Significant improvements in the transient response interaction reaction times and low steady state output interaction achieved using passive compensation and output feedback alone. Simplification of the closed loop configuration is proposed in the final implementation without performance penalties.