published_or_final_version / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

A presente tese trata do estudo dos estimadores algébricos aplicados a sistemas de controle. Tais estimadores são filtros variantes no tempo que estimam as derivadas dos sinais de entrada e funcionam como uma alternativa ao uso de observadores. Este trabalho inclui uma contribuição teórica que permite determinar um limite superior do erro do estimador algébrico. Também, mostramos um resultado que garante estabilidade em malha fechada no contexto do princípio da separação para esta classe particular de sistemas. Um exemplo de levitação magnética baseado em linearização exata com estimadores algébricos de derivadas até segunda ordem implementados digitalmente é tratado com detalhe. Simulações em computador são apresentadas mostrando excelentes resultados. / This thesis deals with the algebraic estimators and their application in closed loop control systems. The algebraic estimators can be implemented as time-varying filters that produce an estimation of the derivatives of the input signal, and they can be an interesting alternative for substituting classical observers. This work includes a theoretic contribution that allows to compute a bound of the estimation error of the algebraic estimator. Furthermore it is shown that any derivative estimator that respects this bound will assure closed loop stability in the context of the separation principle, at least for a class of nonlinear systems. An example of magnetic levitation based on exact linearization and in closed loop with an estimator of the first and second derivatives is considered. A digital implementation of the algebraic estimation is also discussed, and simulations are presented, showing excellent results.

A presente tese trata do estudo dos estimadores algébricos aplicados a sistemas de controle. Tais estimadores são filtros variantes no tempo que estimam as derivadas dos sinais de entrada e funcionam como uma alternativa ao uso de observadores. Este trabalho inclui uma contribuição teórica que permite determinar um limite superior do erro do estimador algébrico. Também, mostramos um resultado que garante estabilidade em malha fechada no contexto do princípio da separação para esta classe particular de sistemas. Um exemplo de levitação magnética baseado em linearização exata com estimadores algébricos de derivadas até segunda ordem implementados digitalmente é tratado com detalhe. Simulações em computador são apresentadas mostrando excelentes resultados. / This thesis deals with the algebraic estimators and their application in closed loop control systems. The algebraic estimators can be implemented as time-varying filters that produce an estimation of the derivatives of the input signal, and they can be an interesting alternative for substituting classical observers. This work includes a theoretic contribution that allows to compute a bound of the estimation error of the algebraic estimator. Furthermore it is shown that any derivative estimator that respects this bound will assure closed loop stability in the context of the separation principle, at least for a class of nonlinear systems. An example of magnetic levitation based on exact linearization and in closed loop with an estimator of the first and second derivatives is considered. A digital implementation of the algebraic estimation is also discussed, and simulations are presented, showing excellent results.

Cette thèse traite de la compensation magnétique de pesanteur. Tout d’abord, des expériences de lévitation magnétique de fluides sont interprétées à l’aide d’un potentiel magnéto-gravitationnel SL. Puis, l’utilisation d’une méthode générale d’analyse de la force magnétique grâce aux harmoniques du champ magnétique est développée. Elle souligne l’importance et le rôle de chacun des trois premiers harmoniques du champ magnétique sur les configurations de forces résultantes inhérentes à la compensation magnétique de pesanteur. En géométrie cylindrique (invariante par translation) diverses combinaisons de forces d’origines magnétique, gravitationnelle et centrifuge offrent des perspectives nouvelles pour la lévitation magnétique. Une combinaison judicieuse des forces magnétiques et centrifuges permet de compenser exactement la pesanteur sur des matériaux diamagnétiques. En géométrie axisymétrique (invariante par rotation), le dimensionnement de stations de lévitation d’oxygène, techniquement réalisables (NbTi@4,2K), est présenté. Ces stations permettent de léviter des volumes d’oxygène supérieurs à 1 litre avec des inhomogénéités inférieures à 1%. La constitution de ces stations rend possible les variations spatiales et temporelles des configurations d’accélérations résultantes. Enfin, la compensation magnétique dynamique de gravité, à l’aide d’une station de lévitation réelle, est étudiée afin de simuler des phases d’accélération ou de décélération d’engins spatiaux / The thesis deals with magnetic gravity compensation. First of all magnetic levitation experiments are explained with the help of a magneto-gravitational potential SL. Next, a general analysis method of the magnetic force is developed which employs magnetic field harmonics. The method underlines both the significance and role of the first three magnetic field harmonics on the resulting forces inherent in magnetic gravity compensation. In cylindrical geometry – with translational invariance – various combination of magnetic, gravitational and centrifugal forces open new possibilities for the magnetic levitation. A suitable combination of both magnetic and centrifugal forces allows exactly compensating gravity on diamagnetic materials. In axisymmetric geometry – with rotational invariance – designs of feasible oxygen magnetic levitation stations are introduced (NbTi@4,2K). Levitation of oxygen volumes more than one litre with inhomogeneities less than 1% can be accomplished within these magnetic levitation facilities. The constitution of the stations makes possible both spatial and temporal variations of the resulting acceleration configurations. At last the dynamic magnetic compensation of gravity with a real coil system is studied so as to simulate both acceleration and deceleration of spaceships

The subject of this thesis is the real-time implementation of algebraic derivative estimators as observers in nonlinear control of magnetic levitation systems. These estimators are based on operational calculus and implemented as FIR filters, resulting on a feasible real-time implementation. The algebraic method provide a fast, non-asymptotic state estimation. For the magnetic levitation systems, the algebraic estimators may replace the standard asymptotic observers assuring very good performance and robustness. To validate the estimators as observers in closed-loop control, several nonlinear controllers are proposed and implemented in a experimental magnetic levitation prototype. The results show an excellent performance of the proposed control laws together with the algebraic estimators. / O tema dessa dissertação é a implementação em tempo real dos estimadores algébricos de derivadas como observadores no controle não-linear de levitação magnética. Esses estimadores são baseados no cálculo operacional e implementados como filtros FIR, resultando em uma implementação viável em tempo real. O método algébrico permite estimar os estados do sistema de maneira rápida e não-assintótica. Para os sistemas de levitação magnética, os estimadores algébricos podem substituir os observadores assintóticos assegurando boas propriedades de robustez e performance. A fim de validar os estimadores como observadores no controle em malha fechada, vários controladores não-lineares são propostos e implementados em um protótipo experimental. Os resultados mostram uma excelente performance dos controladores propostos juntamente com os estimadores algébricos.

The aortic valve maintains unidirectional blood flow between the left ventricle and the systemic circulation. When diseased, the valve is replaced either by a mechanical or a bioprosthetic heart valve, that carry issues such as thrombogenesis, long term structural failure, and calcification, necessitating the development of more structurally and biologically sufficient long-term replacements. Tissue engineering provides a possible avenue for development, combining cells, scaffolds, and biochemical factors to regenerate tissue. The overall goal of this dissertation was to create a foundation for the rational design of a tissue engineered aortic valve. The novel approach taken in this thesis research was to view each of the three leaflets as a laminate structure. The first three aims consider the leaflet as a laminate structure comprising of layers of collagen, elastin, and glycosaminoglycans (GAGs). In the first aim, the effect of GAGs on the tensile properties and stress relaxation in the leaflet was investigated, by removing GAGs through increasing amounts of hyaluronidase. A decrease in GAGs led to significantly higher elastic moduli, maximum stresses, and hysteresis in the leaflet. In the second aim, the 3D elastic fiber network of the leaflet was characterized using immunohistochemistry and scanning electron microscopy. This structure was found to have regionally varying thicknesses and patterns. In the third aim, a novel hydrogel-fiber composite design was proposed to match the anisotropy of the leaflet. This composite composed of aligned electrospun poly(ε-caprolactone) (PCL) within a poly(ethylene glycol) diacrylate (PEGDA) matrix. Surface modification and embedding of the PCL did not significantly alter the anisotropy or strength of the underlying PCL scaffold, providing the basis for an anisotropic, biocompatible scaffold. In the last aim, a novel co-culture model was designed using magnetic levitation as a layered structure of valvular endothelial cells and interstitial cells. This technique was used to create co-culture models within hours, while maintaining cell phenotype and function, and inducing extracellular matrix formation, as shown by immunohistochemical stains and their gene expression profiling. The overall result of this dissertation is a clearer understanding of the layered structure-function relationship of the aortic valve, and its application towards heart valve tissue engineering.

After decades of standstill in intercity passenger rail in the United States, the Obama administration recently started major initiatives to implement high-speed ground transportation projects that are expected to improve the nation's transportation system significantly, addressing most prevailing issues like congestion and energy prices while having positive effects on the economy. This study evaluates and compares two high-speed ground transportation systems that have the potential to improve intercity passenger transportation in the United States significantly: the wheel-on-rail high-speed system and the high-speed maglev system. Both high-speed ground transportation systems were evaluated with respect to 58 characteristics organized into 7 categories associated with technology, environmental impacts, economic considerations, user-friendliness, operations, political factors, and safety. Based on the performance of each system in each of the 58 characteristics, benefit values were assigned. In order to weight the relative importance of the different characteristics, a survey was conducted with transportation departments and transportation professionals. The survey produced weighting factors scoring each of the 58 characteristics and the 7 categories. Applying a multi-criteria decision making (MCDM) approach, the overall utility values for either system were calculated based on the benefit values from the systems comparison and the weighting factors from the survey. It was shown that the high-speed maglev system is generally slightly superior over the wheel-on-rail high-speed system. Because the magnitude of the difference in the overall performance of both transportation systems is not very big, it is recommended that every project in the high-speed intercity passenger transportation market consider both HSGT systems equally.

Current research on thermal effects on guideways has addressed many aspects of the behavior of guideways using two-dimensional models. The two-dimensional models are acceptable for existing guideway designs, in which cross sectional shapes are uniform along the length of the guideway. However, three-dimensional models are necessary for a modular design, in which the track structures that interact with Maglev vehicles are made separately and are assembled into the support structure, and in which the cross sectional shapes are not uniform. A three-dimensional numerical model of the thermal environment, in which the effect of partial shading is taken into account, is implemented for the study of guideway behavior under various thermal environments. The numerical model of the thermal environment is calibrated to the experimental results under the thermal environment at Austin, Texas, and is extrapolated to predict the behaviors of guideways under the thermal environment in Las Vegas, Nevada, which is one of the candidate sites for the implementation and deployment of the high speed Maglev transportation system. This study addresses the suitability of a modular steel guideway design under such a thermal environment. Characteristics of the behavior of guideways under various thermal environments are identified, and the behavior of guideways under the effect of partial shading is summarized. / text

Made available in DSpace on 2014-12-17T14:55:23Z (GMT). No. of bitstreams: 1 JossanaMSF.pdf: 3270599 bytes, checksum: 40178fe964bc435931b6916c9599f55a (MD5) Previous issue date: 2006-11-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work presents a model of bearingless induction machine with divided winding. The main goal is to obtain a machine model to use a simpler control system as used in conventional induction machine and to know its behavior. The same strategies used in conventional machines were used to reach the bearingless induction machine model, which has made possible an easier treatment of the involved parameters. The studied machine is adapted from the conventional induction machine, the stator windings were divided and all terminals had been available. This method does not need an auxiliary stator winding for the radial position control which results in a more compact machine. Another issue about this machine is the variation of inductances array also present in result of the rotor displacement. The changeable air-gap produces variation in magnetic flux and in inductances consequently. The conventional machine model can be used for the bearingless machine when the rotor is centered, but in rotor displacement condition this model is not applicable. The bearingless machine has two sets of motor-bearing, both sets with four poles. It was constructed in horizontal position and this increases difficulty in implementation. The used rotor has peculiar characteristics; it is projected according to the stator to yield the greatest torque and force possible. It is important to observe that the current unbalance generated by the position control does not modify the machine characteristics, this only occurs due the radial rotor displacement. The obtained results validate the work; the data reached by a supervisory system corresponds the foreseen results of simulation which verify the model veracity / Este trabalho apresenta um modelo para a m?quina de indu??o sem mancais com bobinado dividido. O principal objetivo consiste na obten??o do modelo da m?quina para que possam ser implementados controladores mais eficientes. Para se alcan?ar tal modelo, fez-se uso dos mesmos artif?cios utilizados para as m?quinas convencionais adotados na literatura, o que possibilitou um manuseio simplificado das vari?veis envolvidas. A m?quina estudada ? uma adapta??o de uma m?quina de indu??o convencional, o que foi poss?vel dividindo-se os enrolamentos do estator e tornando acess?veis todos os seus terminais. Essa t?cnica dispensa o acr?scimo de um outro enrolamento ao estator para a realiza??o do controle de posi??o radial, o que resulta em uma m?quina mais compacta. Uma outra caracter?stica dessa m?quina ? a varia??o da matriz de indut?ncias em fun??o do deslocamento radial do rotor, a varia??o do entreferro produz varia??es no fluxo e conseq?entemente nos valores de indut?ncias tanto pr?prias quanto m?tuas. O modelo da m?quina convencional pode ser utilizado para a m?quina sem mancais quando o rotor estiver fixo no centro, por?m em situa??es de deslocamento radial esse modelo falha e n?o pode ser? plicado. A m?quina em quest?o possui dois conjuntos motor+mancal, ambos de quatro p?los, e foi projetada com seu rotor na posi??o horizontal, o que incluiu algumas dificuldades ? implementa??o. O rotor utilizado possui caracter?sticas peculiares, o qual ? projetado de acordo com as exig?ncias da m?quina, a fim de render o maior torque e for?a poss?veis. ? importante observar que o desbalanceamento de correntes, gerado pelo controle de posi??o radial, n?o modifica os par?metros da m?quina, isso apenas ocorre devido ao deslocamento radial do rotor. Os resultados apresentados viabilizaram a valida??o do trabalho, os dados obtidos atrav?s de um sistema supervis?rio condizem com os previstos em simula??o, o que atesta a veracidade do modelo

The subject of this thesis is the real-time implementation of algebraic derivative estimators as observers in nonlinear control of magnetic levitation systems. These estimators are based on operational calculus and implemented as FIR filters, resulting on a feasible real-time implementation. The algebraic method provide a fast, non-asymptotic state estimation. For the magnetic levitation systems, the algebraic estimators may replace the standard asymptotic observers assuring very good performance and robustness. To validate the estimators as observers in closed-loop control, several nonlinear controllers are proposed and implemented in a experimental magnetic levitation prototype. The results show an excellent performance of the proposed control laws together with the algebraic estimators. / O tema dessa dissertação é a implementação em tempo real dos estimadores algébricos de derivadas como observadores no controle não-linear de levitação magnética. Esses estimadores são baseados no cálculo operacional e implementados como filtros FIR, resultando em uma implementação viável em tempo real. O método algébrico permite estimar os estados do sistema de maneira rápida e não-assintótica. Para os sistemas de levitação magnética, os estimadores algébricos podem substituir os observadores assintóticos assegurando boas propriedades de robustez e performance. A fim de validar os estimadores como observadores no controle em malha fechada, vários controladores não-lineares são propostos e implementados em um protótipo experimental. Os resultados mostram uma excelente performance dos controladores propostos juntamente com os estimadores algébricos.