No description available.

The Variable Displacement Engine (VDE) is a new generation of engines that are designed to decrease the fuel consumption at the cruise speed of a vehicle. The isolation of the VDE's new vibration pattern is beyond the capabilities of conventional mounts and bushings. Consequently, in this thesis, novel active and semi-active solutions are proposed to develop various semi-active and active hydraulic bushing proof-of-concept systems that may solve the isolation problem in a VDE system. <br /><br /> The dynamic stiffness response, which is the transfer function that relates the engine displacement to the transmitted force, is normally used as the key design criterion for engine mounts and bushings. In this thesis, a linear mathematical model of a conventional hydraulic bushing is purposed. The validity of the mathematical model is confirmed by an experimental analysis, and the various parameters in the dynamic stiffness equation are evaluated. The experimental results indicate that the dynamic stiffness frequency response of the conventional hydraulic bushing has both soft and stiff regions. The soft region is limited to low frequencies. For the VDE isolation, the goal is to provide a soft bushing for a wider range of frequencies than a conventional bushing can accommodate. Addition of a short inertia track, similar to a decoupler used in conventional hydraulic engine mounts, may be used to extend the soft region of a conventional hydraulic bushing, and the experimental results validate it. <br /><br /> Since the short inertia track provides no additional damping, a supplementary Magnetorheological (MR) valve is also devised. The MR valve has the advantage to minimize the amount of MR fluid used, which significantly reduces the cost of the overall system. The novel valve allows the damping coefficient of the bushing assembly to be controlled by varying the electrical current input to a solenoid coil. A mathematical model is derived for the MR bushing, and is validated experimentally. <br /><br /> In addition, an active bushing to solve the VDE isolation problem is purposed in this thesis. In this bushing, a magnetic actuator, composed of a permanent magnet and a solenoid coil, is included in the active bushing. This active chamber affects the dynamic stiffness response of the bushing by altering the bushing's internal pressure. The nonlinear equation of motion of the permanent magnet is linearized and is incorporated into the new mathematical model of the system. The new purposed model for the active bushing is in good agreement with the experimental results. This active chamber is also proved capable of producing complex dynamic stiffness frequency response. <br /><br /> The conclusion is that the proposals in this thesis can contribute to the isolation of the vibration pattern, imposed by the application of a VDE system.

The Variable Displacement Engine (VDE) is a new generation of engines that are designed to decrease the fuel consumption at the cruise speed of a vehicle. The isolation of the VDE's new vibration pattern is beyond the capabilities of conventional mounts and bushings. Consequently, in this thesis, novel active and semi-active solutions are proposed to develop various semi-active and active hydraulic bushing proof-of-concept systems that may solve the isolation problem in a VDE system. <br /><br /> The dynamic stiffness response, which is the transfer function that relates the engine displacement to the transmitted force, is normally used as the key design criterion for engine mounts and bushings. In this thesis, a linear mathematical model of a conventional hydraulic bushing is purposed. The validity of the mathematical model is confirmed by an experimental analysis, and the various parameters in the dynamic stiffness equation are evaluated. The experimental results indicate that the dynamic stiffness frequency response of the conventional hydraulic bushing has both soft and stiff regions. The soft region is limited to low frequencies. For the VDE isolation, the goal is to provide a soft bushing for a wider range of frequencies than a conventional bushing can accommodate. Addition of a short inertia track, similar to a decoupler used in conventional hydraulic engine mounts, may be used to extend the soft region of a conventional hydraulic bushing, and the experimental results validate it. <br /><br /> Since the short inertia track provides no additional damping, a supplementary Magnetorheological (MR) valve is also devised. The MR valve has the advantage to minimize the amount of MR fluid used, which significantly reduces the cost of the overall system. The novel valve allows the damping coefficient of the bushing assembly to be controlled by varying the electrical current input to a solenoid coil. A mathematical model is derived for the MR bushing, and is validated experimentally. <br /><br /> In addition, an active bushing to solve the VDE isolation problem is purposed in this thesis. In this bushing, a magnetic actuator, composed of a permanent magnet and a solenoid coil, is included in the active bushing. This active chamber affects the dynamic stiffness response of the bushing by altering the bushing's internal pressure. The nonlinear equation of motion of the permanent magnet is linearized and is incorporated into the new mathematical model of the system. The new purposed model for the active bushing is in good agreement with the experimental results. This active chamber is also proved capable of producing complex dynamic stiffness frequency response. <br /><br /> The conclusion is that the proposals in this thesis can contribute to the isolation of the vibration pattern, imposed by the application of a VDE system.

<p>The untethered transfer of energy and scalability of magnetic actuators enables functionality to an otherwise passive system. For example, wireless magnetic actuation can turn static 2D and 3D cell cultures into a more physiologically-relevant dynamic environment while limiting contamination. Moreover, indwelling catheters and implantable sensors are typically stationary devices that are notorious for their short lifespan when implanting into the body due to immune responses. Magnetic microactuators may be used for wireless actuation for in situ removal of biological materials accumulated on chronically implanted devices. In this dissertation, I will demonstrate examples of novel biomedical microdevices enabled by magnetic actuation for added functional benefits. First, I will describe a soft polymer magnetic actuator that can facilitate the study of a physiologically relevant cell culturing system. By cyclically stretching an extracellular matrix protein in a 3D cell culture, this system can elucidate the process by which breast cancer cells respond to a dynamic environment in the lungs. The fibrillar fibronectin suspended across the body of the magnetic actuator provides a matrix representative of early metastasis for 3D cell culture that has not yet been recapitulated in vitro until now. Our results demonstrate a clear suppressive cellular response due to cyclic stretching that has implications for a mechanical role in the dormancy and reactivation of disseminated breast cancer cells to macrometastases. As a second application, I will demonstrate the use of magnetic microactuators to remove biofouling on an implantable biosensor in order to prolong its functionality. The results of our work suggest that the motion of the actuator on the sensor surface can maintain biosensor signal integrity and prevents the downstream effects of the foreign body response. Additionally, I will present the design and proof of concept testing of a novel aspiration thrombectomy catheter meant to improve the engagement between the catheter and the blood clot being removed. Preliminary results demonstrate the added benefit of incorporating a microstructure in the inner diameter of the catheter meant to increase the retraction force aspiration catheters have when retrieving corked emboli at the catheter tip. </p> <p><br></p>

Cette étude a été motivée par les nombreux avantages du procédé de micromoulage, qui couple la croissance électrolytique et la localisation du film avec un moule en résine épaisse. Ce procédé permet en effet la réalisation de micro-objets, dont les dimensions sont uniquement dépendantes de la résolution des techniques de lithographie employées pour définir les moules en résine. Le micromoulage permet donc de réaliser des microstructures métalliques et est compatible avec la technologie MEMS. Nous avons mis en évidence l’influence de différents paramètres expérimentaux dans le cadre de l’étude de la croissance électrolytique du samarium-cobalt en solution aqueuse dans une cellule de Hull. Cette étude nous a permis de déterminer plusieurs points de fonctionnement conduisant à des teneurs en samarium et des épaisseurs élevées : jusqu'à 50 % de samarium et plusieurs microns d’épaisseur. En outre, un certain nombre d’hypothèse ont été émises, qui lient le procédé d’élaboration et le mécanisme de croissance. Nous avons aussi réussi a montré qu’il est possible de réaliser des micromotifs de plusieurs microns d’épaisseur contenant un rapport Sm/(Sm+Co) relativement élevé (10 %) et une faible contamination en oxygène (8 %). / This study was motivated by the advantags of micromolding process, which couples the electrolytic growth and location of the film with a thick resin mold. This method makes it possible the achievement of micro-objects, the dimensions of which are only dependent on the resolution of the lithographic techniques used to define the resin molds. The micromolding can therefore produce metal microstructures and is compatible with MEMS technology. We have highlighted the influence of various experimental parameters in the context of the study of the electrolytic growth of samarium-cobalt in aqueous solution in a Hull cell. this study allowed us to identified several operating points resulting in samarium contents and high thicknesses up to 50% of samarium and several microns thick. In addition, a number of hypotheses have been put forward, which link the process of development and growth mechanism. We also successfully showed that it is possible to create micropatterns of several microns thick report containing Sm / (Sm + Co) relatively high (10%) and low oxygen contamination (8%).

Resumo: Este trabalho apresenta o desenvolvimento de uma análise teórica do desempenho de um sistema de controle ativo utilizando mancais magnéticos como atuadores de não-contato para a redução de vibrações em rotores. São analisados três modelos de rotores, sendo que em um deles aplica-se apenas o controle feedback e os outros são suportados apenas por mancais magnéticos, os quais também são os atuadores do controlador. Assim, Luna arquitetura de controle tipo feedforward é empregada sobreposta ao sistema de controle feedback dos atuadores nestes dois modelos, sendo urna análise realizada em relação ao desempenho do sistema de controle quanto às diferentes geometrias de distribuição de massa acopladas ao eixo do rotor. O enfoque principal deste trabalho é voltado para a análise do desempenho do sistema de controle em função da posição e quantidade dos sensores de erro (onde se deseja minimizar as vibrações) em relação à posição dos atuadores e das forças de excitação. As excitações são do tipo síncronas e sub-síncronas que normalmente aparecem em rotores com elevadas velocidades de rotação, como as turbomáquinas. Também é realizada urna análise das forças de controle necessárias a serem aplicadas pelos atuadores para se obter urna redução dos níveis de vibração do rotor na posição dos sensores de erro do sistema feedforward. A análise é executada empregando modelos de rotores desenvolvidos pelo método da matriz de impedância. Esta pesquisa também apresenta Luna aplicação da técnica de controle Feedforward em acústica, que realiza a depuração da voz para comunicação em ambientes ruidosos. / Abstract: This research work brings a theoretical analysis of a control system performance that uses magnetic bearings as non-contact actuators to reduce rotor vibrations. It is analyzed three rotor models, in which one of them operates under the feedback control only. The other models are supported by magnetic bearings only, which also are the controller system actuators. Thus, a feedforward control scheme is applied over the feedback control inherent to the AMB control circuit. The analysis is carried out over these two last models regarding to the control performance for different geometry of mass distribution along the rotor. The focus of this work is to analyze the controller performance according to the sensor quantity and placement (where the vibrations are desired to be minimized) regarding to the actuator position and to the exciting forces. The subsynchronous and synchronous excitations are considered here since they frequently occur in high rotating speed rotors, as in the turbomachinery scenario. Also, the control force required by the actuators is monitored according to the sensors placement to reduce the local vibrations level and the analysis was carried out using the impedance matrix rotor modeling. Further, this work brings a modeling and an application of the feedforward active control scheme in the acoustics field used for voice extraction for communication in noisy environments. / Orientador: Luiz de Paula do Nascimento / Coorientador: Vicente Lopes Junior / Banca: Gilberto Pechoto de Melo / Banca: Kátia Luchese Cavalca Dedini / Mestre

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-14Bitstream added on 2014-06-13T18:31:06Z : No. of bitstreams: 1 perini_ea_me_ilha.pdf: 25219962 bytes, checksum: af8e5bb5738ecda8c45a59f9677a5507 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Este trabalho apresenta o desenvolvimento de uma análise teórica do desempenho de um sistema de controle ativo utilizando mancais magnéticos como atuadores de não-contato para a redução de vibrações em rotores. São analisados três modelos de rotores, sendo que em um deles aplica-se apenas o controle feedback e os outros são suportados apenas por mancais magnéticos, os quais também são os atuadores do controlador. Assim, Luna arquitetura de controle tipo feedforward é empregada sobreposta ao sistema de controle feedback dos atuadores nestes dois modelos, sendo urna análise realizada em relação ao desempenho do sistema de controle quanto às diferentes geometrias de distribuição de massa acopladas ao eixo do rotor. O enfoque principal deste trabalho é voltado para a análise do desempenho do sistema de controle em função da posição e quantidade dos sensores de erro (onde se deseja minimizar as vibrações) em relação à posição dos atuadores e das forças de excitação. As excitações são do tipo síncronas e sub-síncronas que normalmente aparecem em rotores com elevadas velocidades de rotação, como as turbomáquinas. Também é realizada urna análise das forças de controle necessárias a serem aplicadas pelos atuadores para se obter urna redução dos níveis de vibração do rotor na posição dos sensores de erro do sistema feedforward. A análise é executada empregando modelos de rotores desenvolvidos pelo método da matriz de impedância. Esta pesquisa também apresenta Luna aplicação da técnica de controle Feedforward em acústica, que realiza a depuração da voz para comunicação em ambientes ruidosos. / This research work brings a theoretical analysis of a control system performance that uses magnetic bearings as non-contact actuators to reduce rotor vibrations. It is analyzed three rotor models, in which one of them operates under the feedback control only. The other models are supported by magnetic bearings only, which also are the controller system actuators. Thus, a feedforward control scheme is applied over the feedback control inherent to the AMB control circuit. The analysis is carried out over these two last models regarding to the control performance for different geometry of mass distribution along the rotor. The focus of this work is to analyze the controller performance according to the sensor quantity and placement (where the vibrations are desired to be minimized) regarding to the actuator position and to the exciting forces. The subsynchronous and synchronous excitations are considered here since they frequently occur in high rotating speed rotors, as in the turbomachinery scenario. Also, the control force required by the actuators is monitored according to the sensors placement to reduce the local vibrations level and the analysis was carried out using the impedance matrix rotor modeling. Further, this work brings a modeling and an application of the feedforward active control scheme in the acoustics field used for voice extraction for communication in noisy environments.

No description available.

This diploma thesis is about the basics of satellite systems, about their sorting, usage and technologies. An important part is the description of the principles controlling and stabilization of the small experimental CubeSat type satellites. The main point is the proposition and construction of the laboratory model of the CubeSat type satellite that should simulate the chosen methods of controlling and stabilization in laboratory conditions. The thesis describes the construction of the electronic parts of the model, the controlling software of the satellite’s processor and user software for easy controlling by PC.