The recently-developed simultaneous solution scheme for solving nonlinear rotordynamic systems running on foil-air bearings (FABs) has overcome the practice of decoupling the air film, foil and rotor equations that has been typically followed to reduce computational burden at the expense of accuracy. However, the published works using the simultaneous solution technique have been limited to a simple bump foil model in which the individual bumps were modelled as independent spring-damper (ISD) subsystems. The overall aim of this thesis is to present methods that enable more realistic FAB models to be integrated into the simultaneous solution scheme, without compromising its efficiency. Two such alternative approaches are presented: (1) the full foil structure modal model (FFSMM) of the bump foil structure; (2) non-parametric system identification of the entire FAB i.e. foil and air film. The FFSMM provides a more realistic model of the bump foil structure since it considers the interaction between the bumps and foil inertia. Although the foil damping is still assumed to be linear, the model presented is adaptable to nonlinear friction forces. The dynamics of the bump foil structure are studied by finite element methods and experimentally validated using a purpose-made corrugated foil structure. The FE result shows that the effect of bump interaction increases the effective stiffness of the FAB. Foil inertia is not important for the range of speeds considered in the thesis, but the experimentally validated fundamental foil resonance of around 2 kHz is within the operating speed range of high-speed turbomachinery. The FFSMM can take into account the curvature of the bearing sleeve, but the effect of this feature is proven to be negligible for the size of bearing used in the study. The FFSMM simulation results are correlated against ISD model results and published experimental maximum film thickness and locus of the journal response. The results of the FFSMM were then compared against experimental results under unbalance response conditions measured from a purpose-built test rig. The rotor was mathematically modelled using rigid body equations of motion, which were validated by modal analysis. The unbalance rotor response results obtained from the FFSMM and experiment both show that the sub-synchronous motion is not only mainly influenced by the increment of unbalance mass, but, to a greater extent, the increment of rotor speed. The findings show good agreement between the model and experimental results. This thesis also presents the non-parametric system identification of a FAB, which is also adaptable to the simultaneous solution scheme. This work is motivated by two advantages: (a) it removes computational limitations by replacing the whole bearing equations by a displacement/force relationship, where the air film effect is taken into account; (b) it can capture complications that cannot be easily modelled, if the identification is based on empirical data. A Recurrent Neural Network (RNN) is trained to identify the full numerical model of a FAB over a wide range of speeds. The identified model of the FAB is adapted into the frequency domain rotor-dynamic simultaneous solution technique by using harmonic balance (HB) methods, thus directly producing the steady-state orbit response. Excellent correlation is demonstrated between the identification technique and the full numerical model under two validation processes: (i) using different sets of input/output data; (ii) the application of the identified RNN-FAB model to HB analysis in lieu of the full numerical model of the FAB.

This dissertation investigates a new design for a magnetostrictive actuator that employs individually controlled coils distributed axially along the magnetostrictive rod. As a quantitative goal, the objective is to show that the multi-coil actuator can operate effectively at frequencies as high as 10,000 Hz with 900 N force and 50 microns of displacement. Conventional, single coil actuators with the same parameters for force and displacement develop significant attenuation in their response at frequencies above the first longitudinal vibration resonance at about 2750 Hz. The goal of the research is to investigate whether multiple coils can effectively increase the frequency range a least four times the range of conventional magnetostrictive actuators. This document derives a new mathematical model of the actuator that represents the spatial distributions of magnetic field and vibration, devises a control design that takes advantage of the multiple inputs to control the displacement of the actuator while consuming minimum electrical power, and describes a prototype multi-coil actuator and experimental system developed to test the idea. The simulations of the multi-coil actuator and control design demonstrate successful transient operation of the actuator over the targeted frequency range with feasible levels of input power and current. Experimental tests of the design, although limited by a computer sampling rate less than 10,000 Hz, are able to validate the predictions of the developed model of the actuator and reproduce the simulated control performance within the constraints of the experimental system.

Yes / The Atkinson-Shiffrin modal model forms the foundation of our understanding of human memory. It consists of three stores (Sensory Memory (SM), also called iconic memory, Short-Term Memory (STM), and Long-Term Memory (LTM)), each tuned to a different time-scale. Since its inception, the STM and LTM components of the modal model have undergone significant modifications, while SM has remained largely unchanged, representing a large capacity system funneling information into STM. In the laboratory, visual memory is usually tested by presenting a brief static stimulus and, after a delay, asking observers to report some aspect of the stimulus. However, under ecological viewing conditions, our visual system receives a continuous stream of inputs, which is segmented into distinct spatio-temporal segments, called events. Events are further segmented into event-segments. Here we show that SM is not an unspecific general funnel to STM but is allocated exclusively to the current event-segment. We used a Multiple-Object Tracking (MOT) paradigm in which observers were presented with disks moving in different directions, along bi-linear trajectories, i.e., linear trajectories, with a single deviation in direction at the mid-point of each trajectory. The synchronized deviation of all of the trajectories produced an event stimulus consisting of two event-segments. Observers reported the pre-deviation or the post-deviation directions of the trajectories. By analyzing observers' responses in partial- and full-report conditions, we investigated the involvement of SM for the two event-segments. The hallmarks of SM hold only for the current event segment. As the large capacity SM stores only items involved in the current event-segment, the need for event-tagging in SM is eliminated, speeding up processing in active vision. By characterizing how memory systems are interfaced with ecological events, this new model extends the Atkinson-Shiffrin model by specifying how events are stored in the first stage of multi-store memory systems.

L’allègement des structures imposé par les réductions de coût se traduit par des structures de plus en plus souples qui les rendent de plus en plus sensibles aux vibrations. Le contrôle des vibrations devient donc un enjeu majeur dans de nombreuses applications industrielles et les limites des matériaux imposent maintenant un recours au contrôle actif de plus en plus fréquent. L’évolution des structures au cours du temps (viellisement, conditions aux limites, architecture, …) pose le problème de la robustesse du contrôle. Par ailleurs, l’actionnement de plus en plus présent dans le domaine mécanique constitue à la fois une source supplémentaire de vibrations, mais aussi de contrôle et d’évolution d’architecture des structures. La thèse s’intéresse au contrôle actif autoadaptatif des vibrations permettant de maintenir automatiquement la performance et la stabilité des structures évolutives. Il s’agit donc de s’affranchir de la connaissance des causes et des informations sur les évolutions. La méthode proposée s’appuie sur un développement modal permettant de limiter le nombre de composants de contrôle et de cibler les modes à contrôler en limitant l’énergie de contrôle. Ainsi, il est nécessaire de reconstruire les caractéristiques du modèle modal indispensables pour réactualiser le contrôle en figeant seulement une structure de modèle. S’affranchissant à la fois des causes d’évolution de la structure et utilisant seulement une structure de modèle, la méthode est généralisable à toute application en mécanique des structures. La méthode proposée, basée sur l’utilisation d’un identificateur exploitant à la fois excitation et réponse de la structure, prend en compte les limites imposées par le contrôleur. Le modèle constitue le lien qui doit être établi entre identificateur et contrôle pour permettre la réactualisation. Par ailleurs, un compromis entre l’objectif d’atténuation des vibrations et les performances de l’identification est alors nécessaire du fait du couplage identification/contrôle apparaissant dans la boucle fermée. Ce compromis est également conditionné par le matériel utilisé. La méthode proposée est exploitée sur une structure discrète mettant en évidence une inversion de formes modales au cours de son évolution qui déstabilise un contrôle figé. Le choix opéré pour répondre aux différents compromis cités ci dessus a conduit à l’utilisation d’un contrôleur classique (LQG) et un identificateur basé sur la méthode des sous-espaces (N4SID). Cette application sur une structure simple a permis de caractériser un certain nombre de limites physiques : la bande passante, densité modale, vitesse d’évolution, Le contrôle modal autoadaptatif proposé s’avère robuste en performance et efficace lorsque la réactualisation est systématique. Une variante conditionnelle, toujours basée sur l’analyse de la réponse de la structure, est enfin proposée pour optimiser le processus de réactualisation afin de suivre plus efficacement les évolutions. / The lightness of structure due to the reduction of cost results in some structures which are more and more flexible. This flexibility makes these structures more sensitive to vibrations. The vibration control becomes an important issue in lots of industrial applications, and now the limitation of materials imposes a requirement of active control more and more frequently.The change of time-varying structure(ageing effect, boundaries conditions, architecture of structure etc)brings the robust problem of control.Further more,the action of device which emerges more and more frequently in mechanical fields introduces not only an additional cause of vibrations,but also a source of control and a source for changing the architecture of structures.The thesis focuses on self-adaptive active control of vibration which permits to keep up automatically the performance and stability of the time-varying structures.So it needs to overcome the knowing about cause and information on the changes.The proposed method relies on a development of modal technology which permits to limit the amount of component in control system and to target on the modes which need to be controlled.So the energy of control is limited. Further more,it needs to reconstruct the characteristics of modal model which are indispensable for updating the control.In this case, only the structure of model is fixed.Overcoming the knowing about cause of change in the structure and using only the structure of model, this method can be generalized for all applications in mechanical structures.The proposed method is based on the utilization of an identifier which uses both the excitation and response of the structure.And this method considers the limitations induced by the controller.The model forms le link which should be established between the identifier and the controller for allowing the updating. Further more, a compromise between the objective of reducing vibrations and the performance of identification is necessary due to the coupling effect of identification/control which appears in the closed-loop. This compromise is also conditioned by the used equipments.The proposed method is carried out on a discrete time-varying structure for showing an inversion of mode shape during its change. This inversion of mode shape destabilises a fixed control system. The operated choices for responding the different previous quoted compromise lead to a classic controller (LQG) and an identifier based on the subspace method (N4SID).This application on a simple structure permitted to characterise some physical limitation: the bandwidth, the modal density and the velocity of change…The proposed self-adaptive modal control is proved to be robust in terms of performance and be efficient when the updating is systematical. Always based on the analysis of the response of the structure, a conditional variant is finally proposed for optimizing the process of updating in order to follow the change more efficiently.

Orientador: Sérgio Kurokawa / Resumo: Sabe-se que existe um modelo de linha bifásica a parâmetros discretos e constantes, desenvolvido diretamente no domínio do tempo. Porém, o fato de considerar os parâmetros longitudinais para uma frequência fixa, faz com que as respostas de corrente e de tensão apresentem um comportamento aproximado. Para melhorar a qualidade das formas de onda, deve-se levar em consideração o efeito da frequência sobre os parâmetros longitudinais. Nesta dissertação foi densenvolvido um modelo de linha de transmissão bifásica a parâmetros discretos, diretamente no domínio do tempo, que leva em consideração o efeito da frequência. A sintetização do mesmo, tanto para as fases quanto para o acoplamento magnético, é representada por meio de uma associação série e paralela de resistores e indutores, onde a quantidade de blocos RL deve ser a necessária para obter o melhor ajuste da resposta em frequência dos parâmetros longitudinais próprios e mútuos. No modelo proposto, as quedas de tensão nas fases produzidas pelo acoplamento magnético, foram calculadas por meio de uma extensão do modelo de Schulze. As equações de corrente e de tensão ao longo da cascata de circuitos π da linha bifásica foram escritas na forma de equação de estado. Tal equação é resolvida utilizando o método de Heun. No processo de validação do modelo proposto, o modelo clássico modal foi utilizado como modelo de referência, tanto para linhas bifásicas que possuem plano de simetria vertical quanto para linhas bifásicas que não pos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It is know that exist a lumped and constant parameters two-phase line model, desenveloped directly in time domain. However, the fact to considerer the longitudinal parameters for a fixed frequency, it does what current and voltage responses present an approximated behavior. To improve the quality of the waveforms must be taked into consideration the frequency effect on the longitudinal parameters. In this dissertation was desenveloped a lumped parameters two-phase transmission line model, directly in time domain, that takes into consideration the frequency effect. The synthesis of the same, both for the phases and for the magnetic coupling, is represented by a series and parallel association of resistors and inductors, where the quantity of RL-blocks must be the necessary to obtain the best adjustment of the frequency response of the own and mutual longitudinal parameters. In the proposed model, the voltage drops in the phases produced by the magnetic coupling, were calculated by an extension of Schulze’s Model. Current and voltage equations along the cascade of π-circuits of the two-phase line were written in the form of state equation. Such equation is solutioned using Heun’s Method. In the validation process of the proposed model, the classical modal model was used as reference model, both for two-phase lines that possess vertical symmetry plane and for two-phase lines that do not possess vertical symmetry plane. / Mestre

Submitted by MIGUEL ANGEL ESPINOZA CRUZ null (maecuni2006i@gmail.com) on 2018-02-25T13:46:23Z No. of bitstreams: 1 Dissertação.pdf: 5516624 bytes, checksum: a926e8b18f63107cea2ad701b1023b13 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-02-26T13:14:09Z (GMT) No. of bitstreams: 1 espinozacruz_ma_me_ilha.pdf: 5516624 bytes, checksum: a926e8b18f63107cea2ad701b1023b13 (MD5) / Made available in DSpace on 2018-02-26T13:14:09Z (GMT). No. of bitstreams: 1 espinozacruz_ma_me_ilha.pdf: 5516624 bytes, checksum: a926e8b18f63107cea2ad701b1023b13 (MD5) Previous issue date: 2018-02-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Sabe-se que existe um modelo de linha bifásica a parâmetros discretos e constantes, desenvolvido diretamente no domínio do tempo. Porém, o fato de considerar os parâmetros longitudinais para uma frequência fixa, faz com que as respostas de corrente e de tensão apresentem um comportamento aproximado. Para melhorar a qualidade das formas de onda, deve-se levar em consideração o efeito da frequência sobre os parâmetros longitudinais. Nesta dissertação foi densenvolvido um modelo de linha de transmissão bifásica a parâmetros discretos, diretamente no domínio do tempo, que leva em consideração o efeito da frequência. A sintetização do mesmo, tanto para as fases quanto para o acoplamento magnético, é representada por meio de uma associação série e paralela de resistores e indutores, onde a quantidade de blocos RL deve ser a necessária para obter o melhor ajuste da resposta em frequência dos parâmetros longitudinais próprios e mútuos. No modelo proposto, as quedas de tensão nas fases produzidas pelo acoplamento magnético, foram calculadas por meio de uma extensão do modelo de Schulze. As equações de corrente e de tensão ao longo da cascata de circuitos π da linha bifásica foram escritas na forma de equação de estado. Tal equação é resolvida utilizando o método de Heun. No processo de validação do modelo proposto, o modelo clássico modal foi utilizado como modelo de referência, tanto para linhas bifásicas que possuem plano de simetria vertical quanto para linhas bifásicas que não possuem plano de simetria vertical. / It is know that exist a lumped and constant parameters two-phase line model, desenveloped directly in time domain. However, the fact to considerer the longitudinal parameters for a fixed frequency, it does what current and voltage responses present an approximated behavior. To improve the quality of the waveforms must be taked into consideration the frequency effect on the longitudinal parameters. In this dissertation was desenveloped a lumped parameters two-phase transmission line model, directly in time domain, that takes into consideration the frequency effect. The synthesis of the same, both for the phases and for the magnetic coupling, is represented by a series and parallel association of resistors and inductors, where the quantity of RL-blocks must be the necessary to obtain the best adjustment of the frequency response of the own and mutual longitudinal parameters. In the proposed model, the voltage drops in the phases produced by the magnetic coupling, were calculated by an extension of Schulze’s Model. Current and voltage equations along the cascade of π-circuits of the two-phase line were written in the form of state equation. Such equation is solutioned using Heun’s Method. In the validation process of the proposed model, the classical modal model was used as reference model, both for two-phase lines that possess vertical symmetry plane and for two-phase lines that do not possess vertical symmetry plane.