Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 100-106).

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 70).

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiv, 145 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-145).

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009. / Includes bibliographical references.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Book, Wayne; Committee Member: Glezer, Ari; Committee Member: Sadegh, Nader. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

The use of piezoelectric materials for actuation, and vibration suppression of thin beams, is the subject of study in this doctoral thesis. The initial focus is set on reducing beam vibrations with resistively shunted piezoelectric patches, where the converted electrical energy is dissipated by the resistor to give an additional damping. The amount of additional damping achieved depends on the value of shunted resistor, the dimensions of the piezoelectric, and its location on the substructure. Hence, the resistively shunted piezoelectric-beam was modelled to determine the optimal values, and to examine its dynamics. A multi-modal model was derived based on the Euler-Bernoulli beam theory, and a reduced non-dimensionalized transfer function was obtained from the multi-modal model. The presented model was derived from assumptions which aptly describe the dynamics of the resistively shunted piezoelectric-beam. The aptness of the presented model in representing the system, over the existing models, was evident from the comparison of the analytical predictions with the existing experimental data. With the model derived, the second part of the work deals with determining the value of resistance which would yield maximum amplitude attenuation (referred as the optimal resistance value). A method for obtaining the optimal resistance value from the analytical model, based on the presence of a fixed-point in the amplitude response, exists in the literature. But, this method cannot be used on the presented analytical model, as it includes the base-damping of the structure. Hence, a different approach was adopted to determine the optimal resistance from the analytical model. Analytical results were also validated with experimental results from a cantilever piezoelectric-beam. The amplitude plots of the first, second, and third modes of the piezoelectric-beam exhibited a softening e ect, indicating a non-linear behaviour of the piezoelectric patches. Hence, a non-linear constitutive equation was required to describe the behaviour of the piezoelectric patches. In the third part of the work, a two-step experimental procedure was devised to construct the non-linear constitutive equation of the piezoelectric actuators. In the first step, the piezoelectric patches were short circuited and a family of displacement curves were obtained for the first, second and third modes of the piezoelectric-beam by base excitation. The pro le of backbone curves from these plots were used to identify the type of non-linear terms required to describe the mechanical domain. In the second step, voltage excitation was used to obtain a similar set of displacement curves. A comparison of the profile of the backbone curves, of the displacement frequency response plot, from the voltage excited data with those from the base excited data, lead to the identification of the non-linear electromechanical coupling term. The constitutive equation, which accounts for the non-linear nature, of the piezoelectric actuator contains (apart from the linear terms) a quadratic strain term, a cubic strain term, and a term with the product of cubic strain and electric field.

Os atuadores hidráulicos são usados em muitas aplicações e áreas de trabalho devido à sua capacidade para manipular grandes forças com baixa inércia, pouca vibração e capacidade de trabalho por longos períodos de tempo. Entretanto, o maior problema no uso destes tipos de atuadores são as características dinâmicas tais como não-linearidade e variação de parâmetros, as quais dificultam seu controle em malha fechada. Assim, para controlar sistemas hidráulicos, é necessário o uso de modelos matemáticos não lineares e a aplicação de leis de controle complexas para obter um seguimento de trajetória com alta precisão. O objetivo principal deste trabalho é a obtenção de um sistema que siga com precisão as trajetórias de referência do tipo senoidais. Para tanto, este trabalho aborda o projeto de uma lei de controle por realimentação de estados (feedback linearization) combinada com o princípio do modelo interno para aplicar no sistema hidráulico de atuação de uma máquina de ensaios de fadiga. O princípio do modelo interno é aplicado utilizando um compensador dinâmico (que contém pólos imaginários com a mesma freqüência que o sinal de referência) num laço externo do sistema linearizado por realimentação de estados. Uma lei de controle do tipo realimentação de estados, considerando os estados do sistema linearizado e os do compensador dinâmico, é projetada para garantir estabilidade no sistema de malha fechada. A fim de avaliar a estratégia de controle proposta são discutidos e apresentados simulações do modelo experimental. / Hydraulic actuators are used in many applications due to their ability in driving large forces with low inertia and little vibration for a long period of time. However, the main problem in controlling these kinds of systems concerns their dynamics, which presents several nonlinearities and parameters variations. Thus, to control hydraulic systems, appropriated nonlinear models and complex control techniques to achieve a stable force regulation with a specified performance are necessary. The purpose of this work is the application of a feedback linearization scheme in the design of a force controller for a hydraulic actuator used in a fatigue test machine. The main control objective considered regards the achievement of sinusoidal force reference tracking. With this aim the internal model principle is applied by using a dynamic compensator (containing imaginary poles with the same frequency of the force reference) in an outer regulation loop. A state feedback control law, considering both the states of the feedback linearized hydraulic system and the ones of the dynamic compensator, is therefore designed in order to stabilize the whole closed-loop system. Experimental model identification and simulation control results are presented and discussed.

Ces travaux de recherche s’inscrivent dans le cadre d’une coopération scientifique entre le Laboratoire Plasma et Conversion d’Energie(LAPLACE) à l’Institut National Polytechnique de Toulouse en France et le Laboratoire des Systèmes Electriques (LSE) de l’Ecole Nationale d’Ingénieurs de Tunis en Tunisie. L’objectif principal de cette étude consiste à proposer une structure de « smart-machines » en vue de l’intégrer dans un réseau de systèmes supervisés et pilotés à distance. A cette fin, nous développons de nouveaux types de capteurs embarqués intelligents et autonomes pour assurer à la fois la supervision et le contrôle des actionneurs électriques tournants. Les différentes contraintes, comme les dimensions, la mesure in situ (directement sur le rotor de ces machines), la robustesse de ces capteurs en milieu à forts champs électromagnétiques, et aussi le faible coût du produit ont orienté notre choix vers les accéléromètres en technologie MEMS (Micro Système Electro Mécanique). Ces composants présentent plusieurs avantages, d’une part par leurs faibles dimensions, et d’autre part par leurs faibles consommations d’énergie. De plus, de par leurs conceptions, les tensions électriques issues des différentes sorties de ces composants sont proportionnelles à des déplacements de petites masses, qui nécessitent la mise en place de différents algorithmes de traitement du signal afin d’extraire la vitesse de rotation à partir ces actionneurs. Cela nous a conduits à employer la variance d’Allan et des algorithmes génétiques pour obtenir la meilleure qualité des mesures données par ces capteurs. Dans la première partie, nous développons une maquette de mesure de la vitesse de rotation d’un moteur en utilisant un système de balais donc une transmission filaire. Ensuite dans la deuxième partie un système sans fils a été mis en place à la fois sur une machine à courant continu et sur une machine asynchrone de 1,5 kW. Ces études nous ont permis d’obtenir, en plus d‘une mesure de la vitesse de rotation et de l’accélération du moteur, une méthode fiable et apte à déceler les défauts de désalignement de l’axe de rotation du moteur ainsi que les vibrations de ce dernier. Enfin, une IHM (Interface Homme Machine) a été conçue, afin de rendre, quasi-transparents vis-à-vis de l’utilisateur les différents post-traitements. Globalement, notre approche permet d’obtenir un système de capteur de vitesse de rotation aussi fiable que ceux existants, avec l’avantage d’être intégré au sein du rotor avec la possibilité de superviser les défauts de désalignement ou de vibration d’un actionneur et ensuite de les transmettre à distance sans fils. / These research works join within the framework of scientific cooperation between two laboratories: LAPLACE at National Polytechnic Institute of Toulouse in France and LSE at National School of Engineers from Tunis in Tunisia. The main objective of this study consists in proposing a structure of “smart-machines” to introduce them in a network of systems supervised and remote controlled. Consequently, we develop new type of intelligent and autonomous embedded sensors to guarantee simultaneously the supervision and the control of the rotating electrical actuators. The several constraints such as : the dimensions, the measure in situ (directly on the rotor of these machines), the robustness of these sensors in very strong electromagnetic field environment, and also the low cost of the product, have oriented our choice to accelerometers in technology MEMS (Micro Electro Mechanical System). These components present different advantages, on one hand by their low dimensions, and on the other hand by their low energy consumption. Moreover, because of their designs, the electrical voltages obtained from the various outputs of these components are proportional to the small masses movement. The using of them requires the implementation of several signal processing algorithms to extract the rotation speed from these actuators. This led us to use the Variance of Allan and the Genetic Algorithms, to obtain the best certainty of measurements given by these sensors. So, in the first part of this study we develop a measurement device of the rotation speed of an actuator by using a system of brooms thus a wired transmission. Then, in the second part a wireless system was set up at the simultaneously on a direct current (DC) machine and on an induction machine of 1,5 kW. These studies allowed proposing, besides a measure of the electrical actuator rotation speed and its acceleration, the reliable method able to determine the fault of misalignment of the actuator rotation axis as well as its vibrations. Finally, an MMI (Man Machine Interface) was designed, to make quasi-transparent according to the user, the different post signal processing’s. Globally, our approach allows obtaining rotation speed sensor system as reliable as those existing, with the advantage to be integrated within the rotor with the possibility to supervise the actuator axis misalignment fault or its vibration and then to transmit them remote by wireless.

Os atuadores hidráulicos são usados em muitas aplicações e áreas de trabalho devido à sua capacidade para manipular grandes forças com baixa inércia, pouca vibração e capacidade de trabalho por longos períodos de tempo. Entretanto, o maior problema no uso destes tipos de atuadores são as características dinâmicas tais como não-linearidade e variação de parâmetros, as quais dificultam seu controle em malha fechada. Assim, para controlar sistemas hidráulicos, é necessário o uso de modelos matemáticos não lineares e a aplicação de leis de controle complexas para obter um seguimento de trajetória com alta precisão. O objetivo principal deste trabalho é a obtenção de um sistema que siga com precisão as trajetórias de referência do tipo senoidais. Para tanto, este trabalho aborda o projeto de uma lei de controle por realimentação de estados (feedback linearization) combinada com o princípio do modelo interno para aplicar no sistema hidráulico de atuação de uma máquina de ensaios de fadiga. O princípio do modelo interno é aplicado utilizando um compensador dinâmico (que contém pólos imaginários com a mesma freqüência que o sinal de referência) num laço externo do sistema linearizado por realimentação de estados. Uma lei de controle do tipo realimentação de estados, considerando os estados do sistema linearizado e os do compensador dinâmico, é projetada para garantir estabilidade no sistema de malha fechada. A fim de avaliar a estratégia de controle proposta são discutidos e apresentados simulações do modelo experimental. / Hydraulic actuators are used in many applications due to their ability in driving large forces with low inertia and little vibration for a long period of time. However, the main problem in controlling these kinds of systems concerns their dynamics, which presents several nonlinearities and parameters variations. Thus, to control hydraulic systems, appropriated nonlinear models and complex control techniques to achieve a stable force regulation with a specified performance are necessary. The purpose of this work is the application of a feedback linearization scheme in the design of a force controller for a hydraulic actuator used in a fatigue test machine. The main control objective considered regards the achievement of sinusoidal force reference tracking. With this aim the internal model principle is applied by using a dynamic compensator (containing imaginary poles with the same frequency of the force reference) in an outer regulation loop. A state feedback control law, considering both the states of the feedback linearized hydraulic system and the ones of the dynamic compensator, is therefore designed in order to stabilize the whole closed-loop system. Experimental model identification and simulation control results are presented and discussed.