No description available.

Many processes involving rotating machinery could benefit from the continuous feedback of force applied to the bearings that support the machinery. Such a system could be used to provide diagnostics for process monitoring in a manufacturing application or to provide information for machine health monitoring. Active Magnetic Bearings (AMBs) have the capability to act concurrently as a shaft force sensor and support bearing. This capability stems from the AMB's control system, which is designed to maintain a specific rotor position, regardless of forces acting on the rotor. Researchers have demonstrated the force sensing ability of AMBs; current state of the art methods typically rely on a direct measurement of magnetic flux density as provided by a Hall probe inserted in the magnetic field. In this work, a system identification approach to force measurement is proposed; the proposed approach is applicable to all active magnetic bearings and does not require Hall probes. Recent developments in system identification of bearing forces (Kasarda et al., 2000) indicate that a different approach is feasible. In the work of Marshall (Marshall et al., 2001), a variety of perturbations are applied to an AMB while the AMB controller signals are interrogated, no outside instrumentation such as force transducers or Hall probes are required. The work of Kasarda and Marshall is the starting point for the work presented here. The initial work was expanded to include a general characterization of air gap for any rotor position. Although this characterization relies on static testing to identify system parameters, the identified parameters can then be used in the measurement of dynamic forces. The identification procedure provides a measurement of effective air gap length. Effective gap length is used to infer the effective position of the rotor with respect to the stator. This measurement is made for several specific rotor locations. The relationship between the effective rotor positions provided by the identification and the rotor positions reported by the AMB system sensors establishes a coordinate transformation. The procedure is also applied at different shaft rotation angles. In this way rotor runout can be identified. / Ph. D.

Studying animal mechanics is crucial in order to understand how signals in the neuromuscular system contribute to an organism’s behaviour and how force-sensing organs and sensory neurons interact. In particular, the connection between the nerves and the muscles responsible for the force generation in the neuromuscular system needs to be established. Knowledge of the locomotion forces can be beneficial for the development of therapies for muscle disorders, neurodegenerative and human genetic diseases, such as muscular dystrophy. The simplicity of the nematode Caenorhabditis elegans’ (C. elegans) nervous system, which is limited to 302 neurons, has made it an excellent model organism for studying animal mechanics which include mechanosensation and locomotion at the neuronal level. The advent of miniaturized force sensing devices has led to the proposal of various approaches for measuring C. elegans locomotion forces. However, these existing devices are relatively complex, involving complicated microfabrication procedures and are incapable of measuring forces exerted by C. elegans in motion. This thesis addresses these shortcomings by introducing a force sensor capable of continuously measuring the forces generated by C. elegans in motion. The system consists of a micropillar-based device made of polydimethylsiloxane (PDMS) only and a vision-based algorithm for resolving the worm force from the deflection of the cantilever-like pillars. The measured force is horizontal and equivalent to a point force acting at half of the pillar height. The microdevice, sub-pixel resolution for visual tracking of the deflection, and experimental technique form an integrated system for measuring dynamic forces of moving C. elegans with force resolution of 3.13 uN for worm body width of 100 um. A simple device fabrication process based on soft-lithography and a basic experimental setup, which only requires a stereo microscope with off-the-shelf digital camera mean that this method is accessible to most biological science laboratories. The results demonstrate that the proposed device is capable of quantifying multipoint forces of moving C. elegans rather than single-point forces for a worm sample. This allows one to simultaneously collect force data from up to eight measurements points on different worm body parts. This is a significant step forward as it enables researchers to explicitly quantify the relative difference in forces exerted by the worm’s different body segments during the worms’ movements. The device’s capability to determine multipoint forces during nematode motion can also generate meaningful data to compare forces associated with different worm body muscles, gaining new understanding on how these muscles function. The forces measured during locomotion in the micropillars could also be used to differentiate mutant phenotypes. Apart from locomotion forces, the device is also capable of conducting concurrent measurement of other locomotion parameters such as speed, body amplitude and wavelength, as well as undulation frequency. This additional information can be useful to further quantify phenotypic behaviour of C. elegans and deepen the understanding of the theory behind worm locomotion forces. The relationship between C. elegans locomotion forces and their environment has also been analyzed by variation of the pillar arrangement and spacing. The results indicate that the microstructured environment significantly affects the worm’s contraction force, locomotion speed and the undulation frequency. In addition, an alternative measurement technique was provided to measure worm forces on other substrates, such that worm locomotion behaviour in varying environments can be investigated further. The combination of the conventional measurement technique with the findings of worm locomotion on a glass substrate reported show promise for biological measurements and other sensing application such as tactile force. Additional functions of on-chip worm selection, sorting, and imaging have also been integrated with the device, rendering its potential to accommodate for high-throughput application of C. elegans force measurement and locomotion studies in the future. The primary contributions of this thesis are centered around four topics: the development of the PDMS micropillar array and its application to study C. elegans locomotion forces, the analysis of C. elegans muscular forces and locomotion patterns in microstructured environments, the investigation of the worm locomotion forces using different substrates and finally the integration of the PDMS micropillar with PDMS microvalve for on-chip worm selection and imaging. Although the results presented in this thesis focus on wild type C. elegans, the method can be easily applied to its mutants and other organisms.

Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

Active magnetic bearings (AMBs) have the ability to act concurrently as support bearings and as load sensing measurement tools. Previous work in the area of AMB force measurement has relied upon basic magnetic equations requiring knowledge of coil currents and air gap lengths. Some researchers have utilized magnetic flux probes to eliminate the need for air gap measurements, but these are limited by physical size constraints and require complex hardware. This thesis presents a new method for measuring forces with AMBs that utilizes multiple current pairs with no gap measurement to provide accurate and precise force predictions. Previous methods for force measurement with AMBs rely on the controlled environment of a laboratory setting for accurate measurements. The goal of this work is to develop a robust force measurement procedure for use in industrial and field applications, as well as the laboratory. The harsh environment of a factory floor makes air gap measurements difficult, which limits the use of current-based force equations. Additionally, the flexibility of AMB-equipped thrust measurement systems (TMSs) to measure many types of forces with little to no reconfiguration or calibration makes them appealing. The multi-point method provides predictions of both shaft force and rotor position using only current pairs without air gap measurements. Static and dynamic load scenarios were investigated to determine the feasibility of this new approach to force measurement. For both, the effects of bearing load and rotor position within the bearing were analyzed. Under dynamic loading, different amounts of unbalance as well as various rotor speeds were used to provide multiple test cases. The multi-point predictions of rotor position were analyzed and compared with the measured rotor positions. It was shown that this new multiple-point method for measuring bearing loads with AMBs provides equivalent or better force predictions to analogous single-point methods for static loads while eliminating the need for measuring rotor position. / Master of Science

Le travail présenté se concentre sur une complète compréhension de l'AFM du point de vue du contrôle. Cette analyse nous permet de proposer des améliorations au fonctionnement standard de l'AFM. L'approche du contrôle joue un rôle important dans tout ce développement mais une profonde compréhension des instruments de physique a été requise.<br />Le second chapitre, a une vue d'ensemble des techniques les plus importantes pour faire fonctionner la microscopie à sonde locale (SPM) et plus précisement l‘AFM. Ce chapitre dévoile les avantages et inconvénients des techniques existantes. Les fonctions les plus basiques de l'AFM sont représenteé. S'en suit un résumé des modes d'opération de contacte (statique) et modes d'opération de non-contacte (dynamique).<br />Le troisième chapitre se concentre sur les interactions du modèle de surface et la dynamique du levier avec la pointe. Une simplification des interactions du modèle de surface est présentée et utilisée comme base pour accomplir des simulations. S'en suit un modèle de levier simplifié et un modèle multimode plus complexe, basé sur la théorie du faisceau avec l'implantation d'un modèle pour une excitation thermique.<br />Le quatrième chapitre présente une application des techniques de l'observateur pour l'AFM. Un courte introduction présente les perturbations de mesures et les perturbations données par la détection au début. Suit ensuite l'introduction théorique de l'observateur et ses applications pour le contrôle. Puis sont présentés deux observateurs d'application pour l'AFM dans une technique de modulation d'amplitude et une nouvelle mesure de force statique. <br />Le cinquième chapitre présente un mode d'opération de l'AFM basé sur la mesure statique de la force d'interaction. Une technique « cold damping » est utilisée dans le but de faire fonctionner le levier dans un régime complètement statique, la description est faite en début de chapitre. Suivent une définition et une description théorique d'un nouveau mode dopération nommé « Cooling Mode ». Les principaux avantages et inconvénients qui sont comparés aux modes d'utilisation standard de l'AFM sont listés pour constater les améliorations des performances et d'en apprécier les limites. L'expérimentation menée prouve que ce concept est concu et identifié dans le texte suivant. Cette information nous permet de concevoir un contrôleur stable dans la technique de placement du pôle. Les résultats de mesures en temps réel sont présentés à la fin du chapitre.

To identify the dynamic model of the treadmill, this study uses the piezoelectricity material (Po1yviny-lidene fluoride, PVDF) to measure the force under treadmill. With this dynamic model, the ground reaction force (GRF) can be derived from the PVDF sensors. The reliability and precision of the GRF results are verified by replacing the PVDF with the traditional load cell (Force measurement devices). To verify the accuracy of treadmill model, this study acquires three different types of GRF signals (marking time, walking and running) from ten subjects. For the marking time case, the correlation coefficients between the actual and predicated GRF signals are approximately 0.98. This study also demonstrates that the proposed model can provide sufficient bandwidth for the walking and running GRF signals. Finally, via comparing the average GRF profile, inter-personal differences of the GRF signal can be observed. Among the three tested locomotion patterns, the marking time GRF has the highest similarity whereas the running GRF signals has the largest variability.

Abstract In this dissertation, we aim to study the acupuncture effect on stroke rehabilitation. To achieve this purpose, a monitoring system for performance evaluation of motor task in functional MRI environment is developed. The hypothesis of the clinical study is that acupuncture stimulation at motor zone of scalp acupoint could modulate the brain activation of motor system. Such modulation effect can be explored by fMRI. So we use the monitoring system can be used to observe patients with predominantly motor deficit without remarkable speech problem. Besides the fMRI findings of motor activation and clinical motor performance will be compared. The monitoring system must be magnetic field compatible, and furthermore, it can also detect very subtle motor performance in the case of stroke during recovery. So the specific requirements of the system challenge the need. The system includes two subsystems. One collects the position signal using a data glove and the other acquires the force signal with a pneumatic system. The understanding of the correlation of the motor task and the brain activation in depth through the integration of the position and force data can therefore be greatly improved. The monitoring system will extend to be the estimation of recovery through the integration of motor task and fMRI. Keyword: functional MRI¡Bmonitoring system¡Bmotor task¡Bforce measurement

Orientador: José Geraldo Trani Brandão / Banca: Luiz Carlos de Queiroz Faenquil / Banca: Mauro Pedro Peres / Resumo: Na fisioterapia existem procedimentos que dependem da percepção manual do fisioterapeuta por estarem relacionados à aplicação de forças graduadas. Alguns estudos demonstraram que há uma grande dificuldade na percepção da força, ocorrendo grande variabilidade em sua aplicação. O objetivo deste estudo foi desenvolver um equipamento portátil para a medida de forças aplicadas por fisioterapeutas durante a realização da técnica de pressão póstero anterior central na coluna lombar e analisar alguns parâmetros envolvidos no método de mobilização articular. Houve variabilidade na forma de aplicação das cargas em diferentes aspectos. Dessa forma, podemos demonstrar com esses resultados, que a percepção manual do fisioterapeuta durante a realização da técnica de pressão póstero anterior central não foi tão precisa comparando os valores estimados com os valores das cargas aplicadas durante o intervalo de coleta. / Abstract: In Physical Therapy there are some procedures that depend on manual sensibility of physical therapist because that involves graded forces. Some studies have shown that there is a great difficulty in the perception of the force, occuring great variability on the application. The purpose of this study is to develop a portable device to measure the forces applied by physical therapists during the procedure of posteroanterior central pressure in the lumbar spine and to analyze some parameter involved in the method of articular mobilization. There was variability in application of the technique in many ways. Therefore, we can show with these results that the manual sensibility of the physical therapists during the application of the posteroanterior central pressure technique wasnþt accurate comparing the estimated values to the actual results obtained during the experiment interval of time. / Mestre