This thesis presents the multivariable controller design and implementation for a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. The positioner is a triangular single-moving part that carries three 3-phase permanent-magnet linear-levitation-motor armatures. The three planar levitation motors not only generate the vertical force to levitate the triangular platen but control the platen's position in the horizontal plane. All 6-DOF motions are controlled by magnetic forces only. The positioner moves over a Halbach magnet matrix using three sets of two-axis Hall-effect sensors to measure the planar motion and three Nanogage laser distance sensors for the vertical motion. However, the Hall-effect sensors and the Nanogage laser distance sensors can only provide measurements of the displacement of all 6-axis. Since we do not have full-state feedback, I designed two Linear Quadratic Gaussian (LQG) multivariable controllers using a recursive discrete-time observer. A discrete hybrid H2/H(infinity) filter is implemented to obtain optimal estimates of position and orientation, as well as additional estimates of velocity and angular velocity for all 6 axes. In addition, an analysis was done on the signals measured by the Hall-effect sensors, and from there several digital filters were tested to optimize the readings of the sensors and obtain the best estimates possible. One of the multivariable controllers was designed to close the control loop for the three-planar-DOF motion, and the other to close the loop for the vertical motion, all at a sampling frequency of 800 Hz. Experimental results show a position resolution of 1.5 micrometers with position noise of 0.545 micrometers rms in the x-and y-directions and a resolution of less than 110 nm with position noise of 49.3 nm rms in z.

Quantitative Feedback Theory (QFT) is a control system design methodology founded on the premise that feedback is necessary only because of system uncertainty. Articulating flexible structures, such as flexible manipulators, present a difficult closed-loop control problem. In such servo systems, the coupling of the rigid and flexible modes and the non-minimum phase dynamics severely limit system stability and performance. The difficulties in controlling these structures is exacerbated by the denumerably infinite number of flexible modes and associated difficulties in developing accurate dynamic models for controller design. As such, the control of articulating flexible structures presents a non-trivial testbed for the design of QFT based robust control systems. This dissertation examines the multi-input multi-output (MIMO) QFT based control of an articulating flexible structure and presents an enhancement of the theoretical basis for the MIMO QFT design methodologies. The control problem under consideration is the active vibration control of an articulating single-link flexible manipulator. This is facilitated by an actuation scheme comprised of a combination of spatially discrete actuation, in the form of a DC motor to perform articulation, and spatially distributed actuation, in the form of a piezoelectric transducer for active vibration control. In the process of developing and experimentally validating the QFT based control system, shortcomings in the theoretical basis for the MIMO QFT design methodologies are addressed. Robust stability theorems are developed for the two main MIMO QFT design methodologies, namely the sequential and non-sequential MIMO QFT design methodologies. The theorems complement and extend the existing theoretical basis for the MIMO QFT design methodologies. The dissertation results expose salient features of the MIMO QFT design methodologies and provide connections to other multivariable design methodologies.

Quantitative Feedback Theory (QFT) is a control system design methodology founded on the premise that feedback is necessary only because of system uncertainty. Articulating flexible structures, such as flexible manipulators, present a difficult closed-loop control problem. In such servo systems, the coupling of the rigid and flexible modes and the non-minimum phase dynamics severely limit system stability and performance. The difficulties in controlling these structures is exacerbated by the denumerably infinite number of flexible modes and associated difficulties in developing accurate dynamic models for controller design. As such, the control of articulating flexible structures presents a non-trivial testbed for the design of QFT based robust control systems. This dissertation examines the multi-input multi-output (MIMO) QFT based control of an articulating flexible structure and presents an enhancement of the theoretical basis for the MIMO QFT design methodologies. The control problem under consideration is the active vibration control of an articulating single-link flexible manipulator. This is facilitated by an actuation scheme comprised of a combination of spatially discrete actuation, in the form of a DC motor to perform articulation, and spatially distributed actuation, in the form of a piezoelectric transducer for active vibration control. In the process of developing and experimentally validating the QFT based control system, shortcomings in the theoretical basis for the MIMO QFT design methodologies are addressed. Robust stability theorems are developed for the two main MIMO QFT design methodologies, namely the sequential and non-sequential MIMO QFT design methodologies. The theorems complement and extend the existing theoretical basis for the MIMO QFT design methodologies. The dissertation results expose salient features of the MIMO QFT design methodologies and provide connections to other multivariable design methodologies.

RESUMO BarÃante, G. M. CONTROLE PID MULTIVARIÃVEL DESCENTRALIZADO: SINTONIA E APLICAÃÃO PRÃTICA. 2011. 88 f. DissertaÃÃo (Mestrado em Engenharia ElÃtrica)-Centro de Tecnologia, Universidade Federal do CearÃ, Fortaleza, Brasil, 2011. Nesta dissertaÃÃo de mestrado, desenvolvem-se projetos de controladores PI (Proporcional-Integral) e PID (Proporcional-Integral-Dervativo) para os casos SISO (Simple- Input, Simple- Output) e MIMO (Multiples- Input, Multiples-Output). A proposta do trabalho à combinar tÃcnica do relà SISO e PID SISO baseado em especificaÃÃes de margem de fase e margem de ganho para sintetizar um mÃtodo de projeto de controladores PID MIMO multivariÃvel com sintonia automÃtica ou auto-sintonia. Uma Ãnfase especial à dada aos projetos de controladores PID MIMO atravÃs do mÃtodo do relà como elemento de identificaÃÃo frequencial das malhas a serem controladas. Dois mÃtodos de projetos MIMO sÃo abordados em profundidade e aplicados em sistemas simulados e em duas aplicaÃÃes prÃticas a saber: um processo formado pelas malhas de uma incubadora neonatal e em um processo de tanques duplos acoplados. Todos estes processos apresentam fortes interaÃÃes entre as malhas de controle. O primeiro mÃtodo de projeto multivariÃvel refere-se a um projeto sequencial no qual os controladores sÃo projetados de forma sistemÃtica e considerando, a cada passo, a interaÃÃo entre as malhas. Esse mÃtodo à eficiente e simples e apresenta vantagens tais como: i) à conceitualmente simples e mantÃm a estrutura descentralizada e sequencial com o projeto SISO das malhas de controle; ii) estabilidade e robustez sÃo garantidos a cada passo do projeto; iii) desde que o mÃtodo seja autoajustÃvel, nenhum conhecimento do processo à requerido. O segundo mÃtodo de projeto de controladores multivariÃveis refere-se a uma generalizaÃÃo do mÃtodo do ÃstrÃm e Wittenmark, tambÃm conhecido como mÃtodo do ponto crÃtico, para sistemas MIMO. Para se projetar controladores PID com essa abordagem, um entendimento do conceito de superfÃcie crÃtica e locais caracterÃsticos para os casos de processos MIMO deve ser bem estabelecido. Este mÃtodo apresenta ainda muitos aspectos a serem pesquisados e propostas para solucionar vÃrios aspectos teÃricos e prÃticos devem ser lanÃados em breve. Aspectos prÃticos e teÃricos do mÃtodo DRF (Decentrilized Relay Feedback) que utiliza nÃo linearidades do tipo relà para processo MIMO sÃo abordados atravÃs de novas soluÃÃes para os mÃltiplos ciclos limites. Por fim, aplicaÃÃes simuladas e experimentais parecem apontar para vantagens do projeto de controladores PID descentralizados atravÃs do mÃtodo do ponto crÃtico, lembrando que a escolha do melhor mÃtodo de projeto sempre depende de vÃrios aspectos tais como da robustez, estabilidade e complexidade. Esgotar este contexto nÃo constitui a proposta deste trabalho. / ABSTRACT Medeiros, G. M. 2011. 88 f. CONTROL PID MULTIVARIABLE DECENTRALIZED: TUNING AND PRACTICAL APPLICATION. Dissertation (Master in Electrical Engineering)-Technological Center, Federal University of CearÃ, Fortaleza, Brazil, 2011. This dissertation develops PI controllers (Proportional-Integral) and PID (Proportional-Integral-Dervativo) projects for SISO (Simple Input Simple Output) and MIMO (Multiple Input Multiple Output). The objective of this study is to combine the techniques of SISO and SISO PID controllers based on specification of gain and phase margins to synthesize a new design method of multivariable MIMO PID controllers with self-tuning or automatic tuning. Special emphasis is given to projects MIMO PID controllers using the relay method as frequency identification of the loops to be controlled. Two MIMO design methods are discussed in this work. These methods are applied in simulation systems and two practical applications: a process formed by neonatal incubator loops and a process of double attached tanks. These processes have strong interaction between control loops. The first method of multivariable design is a sequential design which the controllers are designed systematically and considering the interaction between loops for each step. This method is efficient and simple and has advantages such as: i) decentralized structure and sequential SISO design of control loops, ii) stability and robustness is guaranteed every step of the project; iii) the method is self-adjusting, therefore process knowledge is not required. The second method of multivariable controller design refers to a generalization of the ÃstrÃm and Wittemark method, also known as critical point method for MIMO systems. The concept of critical surface and local characteristics for the cases of MIMO processes must be well established to design PID controllers with this approach. Many theoretical and practical aspects still need to be investigated in this method. Practical and theoretical aspects of the DRF method (Decentralized Relay Feedback) using nonlinearities like relay MIMO process are addressed through new solutions for multiple limit cycles. The present study showed that simulated and experimental applications seem to point to the advantages of decentralized PID controller design that utilizes the critical point method. The choice of the best method of project always depends on several aspects such as the robustness, stability and complexity, context and exhaust which are not the purpose of this study.

Este trabalho faz uma introdução à evolução dos processos de laminação a frio, acionamento e controle dos mesmos, com foco na laminação de encruamento. O principal objetivo é estabelecer um modelo linear dos sistemas de acionamento, que permita o projeto de um controle multivariável. Pretende-se que a robustez do controle multivariável contribua para a eliminação de defeitos associados aos processos de bobinamento e desbobinamento. A eliminação destes defeitos traz um grande retorno econômico em função do grande volume de produção destas instalações. Para isto é desenvolvido um modelo matemático do sistema completo. No modelo são evidenciadas não linearidades associadas à variação dos diâmetros e inércias das bobinas na desenroladeira e enroladeira. Para solucionar esse problema as parcelas contendo as não linearidades são removidas do modelo. Posteriormente essas parcelas são repostas através de malhas feedforward no controle. Para validar o modelo são projetados controladores PID semelhantes aos utilizados no laminador real. Com os resultados obtidos através de simulação, discute-se a validade do modelo comparando-os com os dados do processo real. A partir desse modelo é desenvolvido o modelo linear em espaço de estados, a ser utilizado no projeto do controlador robusto multivariável. Em seguida é desenvolvido o projeto deste controlador multivariável utilizando a técnica LQG/LTR. Finalmente, são discutidos os resultados das simulações, comparando-os com os dados reais da planta. De um modo geral, os resultados apontam para uma boa aproximação entre a planta real e o modelo proposto. / This work is an introduction to the evolution of the processes of cold rolling, drive and control, focusing on skinpass rolling. The main objective is to establish a model of linear drive systems, allowing the design of a multivariable control. It is intended that the robustness of multivariable control contributes to the elimination of defects associated with processes of coiling and uncoiling. The elimination of these defects poses a great economic return due to the large volume of production of these facilities. To achieve this deal it was developed a mathematical model of the complete system. Nonlinearities associated with variation in diameters and inertia reels in desenroladeira and reel are evidenced in the model. To solve this problem the terms containing nonlinearities were removed from the model and, subsequently reintroduced by feedforward control loops. To validate the model, PID controllers were designed in a similar way to those used in real mill. With the results obtained by simulation, we discuss the validity of the model by comparing them with the actual process data. From this model it was developed a linear state space model to be used in the design of robust multivariable controller. After that it was developed the design of this multivariable controller using the technique LQG / LTR. Finally, it was discussed the simulation results, comparing them with actual data of the plant. Overall, the results point to a good approximation of the real plant and the proposed model.

The optimal estimation theory of the Wiener-Kalman filter is extended to cover the situation in which the number of memory elements in the estimator is restricted. A method, based on the simultaneous diagonalisation of two symmetric positive definite matrices, is given which allows the weighted least square estimation error to be minimised. A control system design method is developed utilising this estimator, and this allows the dynamic controller in the feedback path to have a low order. A 12-order once-through boiler model is constructed and the performance of controllers of various orders generated by the design method is investigated. Little cost penalty is found even for the one-order controller when compared with the optimal Kalman filter system. Whereas in the Kalman filter all information from past observations is stored, the given method results in an estimate of the state variables which is a weighted sum of the selected information held in the storage elements. For the once-through boiler these weighting coefficients are found to be smooth functions of position, their form illustrating the implicit model reduction properties of the design method. Minimal-order estimators of the Luenberger type also generate low order controllers and the relation between the two design methods is examined. It is concluded that the design method developed in this thesis gives better plant estimates than the Luenberger system and, more fundamentally, allows a lower order control system to be constructed. Finally some possible extensions of the theory are indicated. An immediate application is to multivariable control systems, while the existence of a plant state estimate even in control systems of very low order allows a certain adaptive structure to be considered for systems with time-varying parameters.

Les travaux entrepris au cours de cette thèse ont permis de concevoir des stratégies de commande de systèmes multivariables (outils d’analyse et méthodes de synthèse) en vue de leur application au développement de lois de commande d’un turbopropulseur.D’un point de vue fonctionnel, un turbopropulseur est un système multivariable comprenant deux grandeurs de commande : le débit carburant à injecter dans la chambre de combustion et le pas de l’hélice, ainsi que deux grandeurs de sortie : la puissance délivrée par l’hélice et sa vitesse de rotation. Ces variables sont fortement couplées, ce qui signifie que des variations de l’une entraînent des écarts sur l’autre. L’objectif de ces travaux est de synthétiser des lois de commande facilement ajustables, permettant de respecter des spécifications classiques en Automatique (temps de réponse, dépassement, erreur statique) et de réduire les couplages entre les différentes grandeurs régulées. Dans ce contexte industriel, les approches décentralisées sans et avec découplage sont envisagées. La stratégie décentralisée pure met en œuvre un correcteur diagonal, ce qui revient à asservir un système par plusieurs boucles monovariables indépendantes. Bien que relativement facile à synthétiser et à implanter, la stratégie décentralisée ne permet pas d’atteindre les performances souhaitées en présence d’interactions importantes. Dans ce cas, il est possible de l’associer à des compensateurs permettant de diminuer les interactions.Une part importante de ces travaux de recherche concerne le développement méthodologique de ces stratégies. La définition d’une stratégie de commande est la première étape. Pour cela, la quantification du niveau d’interaction dans un système se révèle importante. Celle-ci peut être réalisée à l’aide de différentes méthodes et indicateurs qui s’appuient sur les réponses fréquentielles ou temporelles du système, ou encore sur les grammiens de commandabilité et d’observabilité. Une procédure systématique d’analyse des interactions a été proposée afin de déterminer la stratégie de commande la plus adaptée en fonction des interactions. Dans le cas où l’analyse des interactions conduit à adopter une stratégie décentralisée, les régulateurs peuvent être synthétisés à l’aide de méthodes monoboucles ou multiboucles. Les premières ne prennent pas en compte les interactions tandis que les secondes, plus élaborées mais également plus complexes à mettre en œuvre, permettent de les prendre spécifiquement en compte. A la suite de l’analyse de ces méthodes, une étude récapitulative présentant les méthodes préconisées en fonction du procédé et des objectifs, est finalement proposée. Dans le cas où l’analyse des interactions montre un niveau de couplage trop important, il est possible d’associer des compensateurs à la régulation décentralisée. Les compensateurs ont pour but de découpler les commandes vis-à-vis des sorties du procédé. Différentes méthodes et structures de découplage ont été étudiées et comparées. Une procédure de découplage, composée des méthodes considérées comme les plus efficaces a finalement été mise en place. / In this Ph.D. thesis, we explore the different steps of designing a decentralized control applied on a turboprop engine.From the control point of view, the turboprop engine is a TITO (Two-Input Two-Output) process. The fuel flow is used to control the shaft power while the blade pitch angle is used to control the propeller speed. The turboprop presents important couplings between manipulated variables and controlled variables. When the fuel flow changes, the propeller speed is impacted. Similarly, when controlling the blade pitch angle to change the propeller speed to another level, the shaft power is affected, particularly during the transient states. The main objective of this research thesis is to design control laws for the turboprop. Beside technical specifications like response time and overshoot, couplings between loops have to be reduced as much as possible and control laws have to be robust to model uncertainties. For this industrial environment a decentralized strategy (with or without compensators) has been chosen. The decentralized strategy consists in designing monoloop controllers in order to drive the multivariable system. The decentralized strategy presents important benefits, such as flexibility as well as design simplicity, but is not efficient in presence of heavy couplings. In that case, it is possible to use compensators that reduce existing process interactions before designing the monoloop controllers.An important part of this work focuses on the development of these different strategies.The first step is the choice of the control structure, which strongly depends on the level of interaction. Despite the availability of different metrics - based on frequential responses, temporal responses, or Gramian – it is not easy to know which one is the most appropriate. Based on the analysis of couplings with different metrics, a procedure is proposed in order to choose the structure and the controllers design method.If the coupling analysis leads to adopt a decentralized strategy, the controllers can be designed using monoloop or multiloop methods. The first ones are simple but do not take couplings into account, whereas multiloop methods take specifically couplings into account but are more complicated. These tuning methods have been studied and recommendations have finally been made to choose the most appropriated method depending on the process and the requirements.In cases where the couplings analysis reveals a high couplings level, compensators can be associated with the decentralized strategy. The objectives of the compensators are to reduce couplings in the system and to facilitate the design of monoloop controllers. Several decoupling structures have been studied and compared. A decoupling procedure has then been proposed.These methodological studies have been applied to the turboprop engine. Following the coupling analysis, a decentralized strategy with decoupling has been chosen. After following the decoupling procedure and trying different solutions, the inverted decoupler has been adopted. Considering the dynamics of the system and the total decoupling provided by the inverted decoupler, PI controllers have been used and a monoloop tuning method has been chosen. In order to guarantee the desired performances over the whole flight envelope, control laws have been interpolated, using a gain scheduling technique. The structured singular value approach has then been used to demonstrate the robustness of the control laws with model uncertainties. Control laws have finally been implemented in the control software and simulation results have illustrated their good performances.

Esta dissertação tem como objetivo o projeto de um mancal magnético para rodas de reação com aplicação na malha de controle de atitude de satélites. Mancais magnéticos são alternativas aos mancais tradicionais tais como os de esferas ou de lubrificação seco pois trabalham sem contato mecânico entre o rotor e o estator, minimizando assim a fricção entre ambas as partes. Além da minimização do atrito, o ganho em confiabilidade e vida útil da roda de reação é considerável por não apresentar desgastes mecânicos. Devido às consequências de qualquer fricção no movimento relativo entre a inércia (parte rotativa da roda de reação) e o satélite, o mancal torna-se um componente crítico da roda de reação. A fricção se traduz não apenas num maior consumo de potência elétrica, como também na introdução de uma zona morta de atuação em torque, bem como na limitação da vida útil da roda de reação devido ao gradual desgaste do mancal. O mancal proposto possui dois graus de liberdade axiais ativamente controlados e faz uso de ímãs para a estabilização passiva dos demais graus de liberdade. Ao longo do desenvolvimento são apresentados modelos não lineares dos campos magnéticos e das forças atuantes no mancal são encontrados. Com esses modelos, uma otimização é realizada a fim de encontrar melhores características. Um modelo não linear da dinâmica do rotor é desenvolvido e um controle PID capaz de estabilizar o rotor em seu ponto de equilíbrio é apresentado com o objetivo de demonstrar a viabilidade da topologia proposta. / The main objective of this work is to project a magnetic bearing for reaction wheels with application in satellite attitude control. Magnetic bearings are alternatives to traditional bearings such as ball or dry lubrication because they work without mechanical contact between the rotor and the stator thereby minimizing friction between both parts. In addition to minimizing friction, the gain in reliability and lifetime of the reaction wheel is considerable as a consequence of the absence of wear. Because of the consequences of any friction in the relative movement between the inertia (of the reaction wheel) and the satellite ( which is rigidly connected to the satellite body), the bearing becomes a critical component of the reaction wheel. The friction gives rise not only to a greater consumption of electric power, as well as the introduction of a torque dead zone operation, in a reduced lifetime of the reaction wheel due to gradual wear of the bearing. The proposed bearing has two axial degrees of freedom actively controlled and makes use of magnets for the passive stabilization of other degrees of freedom. Nonlinear models of magnetic fields and forces acting on the bearing are presented. With these models, an optimization is performed to find the best bearing characteristics. A nonlinear model rotor dynamics is developed and a PID control capable of stabilizing the active degrees of freedom presented.

A aplicação de técnicas de controle multivariáveis com o auxílio de ferramentas computacionais vem sendo bastante empregada em projetos de sistemas de controle complexos, que tem como base o conceito de variáveis de estado. Neste trabalho, visamos desenvolver um sistema de controle seguidor com realimentação de estados para um protótipo de um sistema de hélices paralelas onde a dinâmica é não linear e possui três graus de liberdade sendo dois graus de liberdade controlados. Serão utilizados dois modelos matemáticos: um modelo linear e um modelo não linear. A representação linear será utilizada para gerar as matrizes de ganho do sistema de controle. O modelo não linear é obtido através de prototipagem virtual no ambiente de desenvolvimento ADAMS®, que utiliza técnicas de modelagem de sistemas multicorpos para a obtenção das equações dinâmicas do movimento. Em seguida o modelo não linear é exportado para o ambiente de simulações em MATLAB®. A simulação é utilizada para verificar se a técnica de controle linear utilizada tem a capacidade de controlar o sistema não linear e analisar o comportamento do conjunto controlador mais a planta não linear já que está sendo feita atribuição de auto-estrutura completa. Os resultados obtidos ilustram o desempenho e a eficiência da metodologia proposta. / The application of multivariable control techniques with the aid of computing tools has been largely used in projects of complex control systems that are based on the concept of state-variables. The objective of this paper is to show the development of a tracking-system with state-feedback for a prototype of a parallel propeller system presenting nonlinear dynamics with three degrees-of-freedom but having only two controlled. Two mathematical models are used: a linear model and a nonlinear model. The linear representation is used to design the gain matrices of the linear control system. The nonlinear model is obtained through the virtual prototyping environment system ADAMS®, using modeling techniques of multi-body systems to obtain the dynamic motion equations. Then, the nonlinear model is exported to SIMULINK® (MATLAB®). The simulation is used to verify if the applied linear control techniques are able to control the nonlinear model and to analyze the system behavior (control system plus nonlinear plant). The design of the control system is done using the entire eigenstructure assignment technique. The results show the performance and the efficiency of the proposed methodology.

Les travaux entrepris au cours de cette thèse ont permis de concevoir des stratégies de commande de systèmes multivariables (outils d’analyse et méthodes de synthèse) en vue de leur application au développement de lois de commande d’un turbopropulseur.D’un point de vue fonctionnel, un turbopropulseur est un système multivariable comprenant deux grandeurs de commande : le débit carburant à injecter dans la chambre de combustion et le pas de l’hélice, ainsi que deux grandeurs de sortie : la puissance délivrée par l’hélice et sa vitesse de rotation. Ces variables sont fortement couplées, ce qui signifie que des variations de l’une entraînent des écarts sur l’autre. L’objectif de ces travaux est de synthétiser des lois de commande facilement ajustables, permettant de respecter des spécifications classiques en Automatique (temps de réponse, dépassement, erreur statique) et de réduire les couplages entre les différentes grandeurs régulées. Dans ce contexte industriel, les approches décentralisées sans et avec découplage sont envisagées. La stratégie décentralisée pure met en œuvre un correcteur diagonal, ce qui revient à asservir un système par plusieurs boucles monovariables indépendantes. Bien que relativement facile à synthétiser et à implanter, la stratégie décentralisée ne permet pas d’atteindre les performances souhaitées en présence d’interactions importantes. Dans ce cas, il est possible de l’associer à des compensateurs permettant de diminuer les interactions.Une part importante de ces travaux de recherche concerne le développement méthodologique de ces stratégies. La définition d’une stratégie de commande est la première étape. Pour cela, la quantification du niveau d’interaction dans un système se révèle importante. Celle-ci peut être réalisée à l’aide de différentes méthodes et indicateurs qui s’appuient sur les réponses fréquentielles ou temporelles du système, ou encore sur les grammiens de commandabilité et d’observabilité. Une procédure systématique d’analyse des interactions a été proposée afin de déterminer la stratégie de commande la plus adaptée en fonction des interactions. Dans le cas où l’analyse des interactions conduit à adopter une stratégie décentralisée, les régulateurs peuvent être synthétisés à l’aide de méthodes monoboucles ou multiboucles. Les premières ne prennent pas en compte les interactions tandis que les secondes, plus élaborées mais également plus complexes à mettre en œuvre, permettent de les prendre spécifiquement en compte. A la suite de l’analyse de ces méthodes, une étude récapitulative présentant les méthodes préconisées en fonction du procédé et des objectifs, est finalement proposée. Dans le cas où l’analyse des interactions montre un niveau de couplage trop important, il est possible d’associer des compensateurs à la régulation décentralisée. Les compensateurs ont pour but de découpler les commandes vis-à-vis des sorties du procédé. Différentes méthodes et structures de découplage ont été étudiées et comparées. Une procédure de découplage, composée des méthodes considérées comme les plus efficaces a finalement été mise en place. / In this Ph.D. thesis, we explore the different steps of designing a decentralized control applied on a turboprop engine.From the control point of view, the turboprop engine is a TITO (Two-Input Two-Output) process. The fuel flow is used to control the shaft power while the blade pitch angle is used to control the propeller speed. The turboprop presents important couplings between manipulated variables and controlled variables. When the fuel flow changes, the propeller speed is impacted. Similarly, when controlling the blade pitch angle to change the propeller speed to another level, the shaft power is affected, particularly during the transient states. The main objective of this research thesis is to design control laws for the turboprop. Beside technical specifications like response time and overshoot, couplings between loops have to be reduced as much as possible and control laws have to be robust to model uncertainties. For this industrial environment a decentralized strategy (with or without compensators) has been chosen. The decentralized strategy consists in designing monoloop controllers in order to drive the multivariable system. The decentralized strategy presents important benefits, such as flexibility as well as design simplicity, but is not efficient in presence of heavy couplings. In that case, it is possible to use compensators that reduce existing process interactions before designing the monoloop controllers.An important part of this work focuses on the development of these different strategies.The first step is the choice of the control structure, which strongly depends on the level of interaction. Despite the availability of different metrics - based on frequential responses, temporal responses, or Gramian – it is not easy to know which one is the most appropriate. Based on the analysis of couplings with different metrics, a procedure is proposed in order to choose the structure and the controllers design method.If the coupling analysis leads to adopt a decentralized strategy, the controllers can be designed using monoloop or multiloop methods. The first ones are simple but do not take couplings into account, whereas multiloop methods take specifically couplings into account but are more complicated. These tuning methods have been studied and recommendations have finally been made to choose the most appropriated method depending on the process and the requirements.In cases where the couplings analysis reveals a high couplings level, compensators can be associated with the decentralized strategy. The objectives of the compensators are to reduce couplings in the system and to facilitate the design of monoloop controllers. Several decoupling structures have been studied and compared. A decoupling procedure has then been proposed.These methodological studies have been applied to the turboprop engine. Following the coupling analysis, a decentralized strategy with decoupling has been chosen. After following the decoupling procedure and trying different solutions, the inverted decoupler has been adopted. Considering the dynamics of the system and the total decoupling provided by the inverted decoupler, PI controllers have been used and a monoloop tuning method has been chosen. In order to guarantee the desired performances over the whole flight envelope, control laws have been interpolated, using a gain scheduling technique. The structured singular value approach has then been used to demonstrate the robustness of the control laws with model uncertainties. Control laws have finally been implemented in the control software and simulation results have illustrated their good performances.