<p>Hasomed GmbH, a German company in the Field of medicine technology, intends to introduce a gait analysis system on the market. The system includes an inertial sensor which collects data used for generating movement patterns of the feet. This thesis describes the development and evaluation of a new version of the sensor, aimed at minimizing costs, maximizing performance and facilitating production.</p><p>Algorithms used in the gait analysis system are sensitive to noise. Noise sources and precautions taken in order to minimize noise levels are described and discussed. By minimizing the physical size of analogue electronics blocks, static noise and occasional high frequency components were substantially reduced.</p><p>New features including internal temperature sensors, firmware update via serial interface, self-test functions and a wireless link were implemented. Additional improvements are e.g. lower power consumption and an extension of the interface from 2 to 256 (theoretical limit) attached devices. By reducing the number of included components and PCB (Printed Circuit Board) layers, together with use of components that do not require advanced soldering techniques, easier and cheaper production was obtained.</p><p>Research and development presented in this thesis resulted in a sensor with overall good performance and new features.</p>

Hasomed GmbH, a German company in the Field of medicine technology, intends to introduce a gait analysis system on the market. The system includes an inertial sensor which collects data used for generating movement patterns of the feet. This thesis describes the development and evaluation of a new version of the sensor, aimed at minimizing costs, maximizing performance and facilitating production. Algorithms used in the gait analysis system are sensitive to noise. Noise sources and precautions taken in order to minimize noise levels are described and discussed. By minimizing the physical size of analogue electronics blocks, static noise and occasional high frequency components were substantially reduced. New features including internal temperature sensors, firmware update via serial interface, self-test functions and a wireless link were implemented. Additional improvements are e.g. lower power consumption and an extension of the interface from 2 to 256 (theoretical limit) attached devices. By reducing the number of included components and PCB (Printed Circuit Board) layers, together with use of components that do not require advanced soldering techniques, easier and cheaper production was obtained. Research and development presented in this thesis resulted in a sensor with overall good performance and new features.

A number of parameters have been identified as characteristic of the walking pattern in patients with INPH. Most of these have been identified through qualitative surveys and manually conducted test batteries. In order to obtain quantitative, standardized and objective measures, which enable studies based on larger patient populations and comparable results, there is a need for a user-friendly system that can measure specific key parameters over time in a reliable manner in everyday clinical work. Step height, width and the variability in the gait cycle are such parameters which are interesting research areas for this group of patient. Problems with balance and gait are very common in other patient groups as well, particularly in neurological diseases such as Parkinson's disease, multiple sclerosis and stroke. This is the reason that the development of this gait analyzer is performed. Giving access to a simple and objective method for estimating gait and balance ability in clinical routine investigations would increase the ability to provide the right kind of treatment, confirm treatment results, and conducting larger research studies. Therefore, this equipment can contribute to the assessment of diseases which contain impaired gait. As a first test of the usability and for the validation of accuracy and repeatability of the equipment a group of healthy volunteers was used. Results from tests on healthy subjects show god repeatability between measurements, for step width at normal gait the difference was -0,2 ±0,34 cm (mean, ±SD) and step height 0,69 ±3,34 cm. The stride time variability in the healthy group where very small 0,00048 ±0,00028 s2 with a difference between test of 0,000019 ±0,00038 s2. Three pilot patients have been tested where we have clearly seen indications of increased stride time variability and reduced step height.

The portability, ease of use and improved accuracy of miniature inertial sensors brought by current microelectromechanical system (MEMS) technology has inspired researchers to develop human movement monitoring system with body-fixed sensors. Although a large number of studies have attempted to explore the use of miniature inertial sensors in estimating walking speed for the past two decades, there still remain some questions regarding applying inertial sensors in estimating walking speed under different walking conditions and for different subject populations. In this thesis, I focus on evaluating and improving the performance of a shank-mounted mounted inertial measurement unit (IMU) based walking speed estimation method. My research can be divided into four parts. The first part was a systematic review regarding the state of the art of current development of the inertial sensor based walking speed estimation method. A total of 16 articles were fully reviewed in terms of sensor specification, sensor attachment location, experimental design and spatial parameter estimation algorithm. In the second part, a comprehensive performance evaluation was conducted, which included the treadmill and overground walking experiments with constraint on the walking speed, stride length and stride frequency. A systematic error was observed in the error analysis of this study, which was adjusted by subtracting the bias by linear regression. In the third part, a post-stroke subject overground walking experiment was carried out with an improved walking speed estimation method that reduced the systematic error caused by previous false initial speed assumption. In addition to walking speed estimation, the gait asymmetry for post-stroke hemiparetic gait was also evaluated with the proposed method. The last part was the sensor error model analysis. We elaborately analyzed and discussed the estimation errors involved in this method in order to completely understand the sensor error compensation in walking speed estimation algorithm design. Two existing sensor error models and one newly developed sensor error model were compared with the treadmill walking experiment, which demonstrated the effect of each sensor error component on the estimation result and the importance of the sensor error model selection. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-08-23 19:38:16.965

This thesis explains the design, fabrication and characterization steps of a high dynamic range CMOS-MEMS capacitive accelerometer array and on-chip environmental sensors for bias drift compensation. Inertial navigation under harsh environments requires a high dynamic range accelerometer that can survive and provide continuous readout accuracy through shock events, while having a large dynamic range to capture fine-scale motions. The dynamic range target is set as 156 dB in accordance with navigation standard macro-electromechanical accelerometers, which corresponds to around 1 mG acceleration resolution in 50 kG input range. The small accelerometer cell design ensures shock survivability (e.g. up to 50 kG) by keeping the stress at the anchors below the fracture strength of thin-film oxide. Arraying multiple accelerometer cells in parallel lowers the fundamental thermomechanical noise limit set by the small mass of the individual accelerometer cells. Resonance frequency staggering between accelerometer cells suppresses ring-down oscillations. Parasitic capacitance of the high-impedance transduction signal is important to mitigate; undercut of the underlying silicon substrate and an aluminum etch of the top metal layer, incorporated in the CMOS-MEMS process flow, reduces the parasitic capacitance and improves sensitivity. PTAT temperature sensors, piezoresistive stress sensors and resonator-oscillators integrated across the accelerometer chip provide high-resolution environmental measurements for the compensation of long-term bias and scale factor drift. Simultaneous measurements from the accelerometer and environmental sensors demonstrate the correlation between environmental variations and long-term drift. Finite-element analysis shows that the scale factor stability of the accelerometer can be improved up to 1 ppm given the sensor array’s measurement resolution. The CMOS-MEMS accelerometer system-on-chip is fabricated in a TowerJazz 0.18 μm CMOS process. The post-CMOS MEMS processing steps are tuned to reduce the top metal milling and sidewall polymer deposition. A reactive ion etch recipe is developed for the removal of the top metal in order to reduce the parasitic capacitance and eliminate the risk of metal creep at spring beam anchors, thereby improve the bias stability. The PTAT temperature sensors have 3.1 mV/K measured sensitivity and 7.1 mK resolution with high repeatability. The compensation of the accelerometer readout for temperature variations down to 7.1 mK translates to 2.6 ppm scale factor stability for the accelerometer. The characterization of the stress sensors through the application of normal stress on the device package leads to an uncertainty in the amount of stress transferred to the stress sensors on the chip surface. The maximum measured stress sensitivity is 36.5 pV/Pa, which leads to 24.7 kPa stress resolution and translates to 1.7 ppm scale factor stability for the accelerometer without taking the stress attenuation into account. The measured sensitivity sets a lower bound on the sensitivity of the stress sensors implying that the stress resolution and the corresponding accelerometer scale factor stability is higher in practice. The measured frequency stability of the resonator-oscillator is 0.4 ppm, thereby the resonance frequency based variations of the accelerometer readout can be compensated to reach up to 0.8 ppm scale factor stability. However, the initial drift in the resonance frequency of the oscillators due to dielectric charging requires a long wait-time before these sensors can be used for accelerometer drift compensation. The accelerometer array is demonstrated to have 23.7 mG/√Hz noise floor and 70 mG bias stability. The maximum input acceleration applied on the device is limited to 4 kG by the split Hopkinson bar test setup. Improvement of the setup to transfer acceleration amplitudes up to 50 kG should validate the designed input range of the accelerometer array and lead to 117 dB dynamic range for the current design. The measurement bandwidth is fundamentally set by the 126 kHz resonance frequency of the accelerometer cells and can be further limited by filtering the readout signal to attenuate the transient oscillations faster. The nonlinearity of the accelerometer response is better than 1.2% in ±10 kG input range; however, it gets up to 19.0% in ±50 kG maximum input range. The long term bias drift of the accelerometer is shown to be correlated with the temperature and stress variations. Compensation of the accelerometer readout based on the stress and temperature sensor measurements leads to an observable improvement in the long term drift. However, the bias stability of the accelerometer is limited by excessive flicker noise in the system, which is believed to result from noise folding from higher frequencies. Suppression of the flicker noise in the system should allow for a more detailed study of the effect of environmental variations on the accelerometer readout and evaluation of more elaborate fitting algorithms for model based prediction and compensation of the bias drift to reach the target bias stability and dynamic range.

Inertial sensing technologies, including accelerometers and gyroscopes, have been invaluable in numerous fields ranging from consumer electronics to healthcare and clinical practices. Inertial measurement units, specifically accelerometers, represent the most widely used microelectromechanical systems (MEMS) devices with excellent and reliable performance. Although MEMS-based accelerometers have many attractive attributes, such as their tiny footprint, high sensitivity, high reliability, and multiple functionalities, they are limited by their complex and expensive microfabrication processes and cumbersome, fragile structures that suffer from mechanical fatigue over time. Moreover, the rigid nature of beams and spring-like structures of conventional accelerometers limit their applications for wearable devices and soft-human machine interfaces where physical compliance that is compatible with human skin is a priority. In this dissertation, the development of novel practical resistive and capacitive-type inertial sensors using liquid metal as a functional proof mass material is presented. Utilizing the unique electromechanical properties of liquid metal, the novel inertial sensor design confines a graphene-coated liquid metal droplet inside tubular and 3D architectures, enabling motion sensing in single and multiple directions. Combining the graphene-coated liquid metal droplet with printed sensing elements offers a robust fatigue-free alternative material for rigid, proof mass-based accelerometers. Resistive and capacitive sensing mechanisms were both developed, characterized, and evaluated. Emerging rapid fabrication technologies such as direct laser writing and 3D printing were mainly adopted, offering a scalable fabrication strategy independent of advanced microfabrication facilities. The developed inertial sensor was integrated with a programmable system on a chip (PSoC) to function as a stand-alone system and demonstrate its application for real-time- monitoring of human health/ physical activity and for soft human-machine interfaces. The developed inertial sensor architecture and materials in this work offer a new paradigm for manufacturing these widely used sensors that have the potential to complement the performance of their silicon-based counterparts and extend their applications.

Câmeras embarcadas em sistemas robóticos móveis com sensoriamento visual geralmente são afetadas pelo movimento de seu suporte quando é necessária a aquisição de imagens com alta confiabilidade. Algumas câmeras disponíveis no mercado já estão equipadas com sistemas de estabilização de imagens, implementados nas lentes da câmera ou no sensor de imagem. Esses sistemas são relativamente caros para serem instalados em sistemas robóticos móveis aéreos ou terrestres de pequeno porte. Outro conceito que tem sido utilizado para alcançar a estabilização consiste em adotar sensores inerciais, algoritmos de visão computacional e aplicação de filtros digitais para estimativa e suavização de movimento. Esta dissertação tem por finalidade apresentar um sistema de estabilização digital de vídeo em conjunto com um acelerômetro para detectar movimentos da câmera. Considera-se que a câmera está instalada sobre plataforma instável ou em veículo em movimento, assim, utiliza-se filtragem robusta para minimizar o efeito da vibração sobre a câmera. Vários experimentos são realizados adicionando vibração em vídeo por meio de simulações em computador. Considera-se também experimentos em ambiente real com a câmera montada em um suporte dentro de um veículo em movimento. A principal contribuição deste trabalho é a realização de um estudo comparativo para analisar a vantagem de se usar uma abordagem robusta entre os métodos de filtragem comumente utilizados em sistemas de estabilização de vídeo. / Embedded cameras in robotic systems usually are susceptible to movements of your basis. The measurements can be affected mainly when they should obtain high performance in actual applications. Although some cameras available on the market are already equipped with an optical image stabilization system, implemented either in the camera lenses or in the image sensor. They are usually expensive to be installed into small aerial or land robotic systems. This dissertation presents a video stabilization system coupled with an accelerometer for motion detection at an unstable platform. It is embedded in a vehicle. Robust filtering is used to minimize vibration effects on the camera. Several experiments were performed, adding either vibrations via computer simulations and taking images from the camera with the vehicle moving. The main contribution of this work is the accomplishment of a comparative study to analyse the advantages of applying a robust approach among others filtering methods that frequently are used to video stabilizing systems.

Due to the recursive and integrative nature of zero-velocity-update-aided (ZUPT-aided) inertial navigation systems (INSs), the error covariance increases throughout each ZUPT-less period followed by a drastic decrease and large state estimate corrections as soon as ZUPTs are applied. For dead-reckoning with foot-mounted inertial sensors, this gives undesirable discontinuities in the estimated trajectory at the end of each step. However, for many applications, some degree of lag can be tolerated and the information provided by the ZUPTs at the end of a step can be made available throughout the step, eliminating the discontinuities. For this purpose, we propose a smoothing algorithm for ZUPT-aided INSs. For near real-time applications, smoothing is applied to the data in a step-wise manner requiring a suggested varying-lag segmentation rule. For complete off-line processing, full data set smoothing is examined. Finally, the consequences and impact of smoothing are analyzed and quantified based on real-data. / <p>QC 20130114</p>

La biomécanique du sport décrit le mouvement humain dans le but d'améliorer la performance et de réduire les blessures. Dans ce contexte, le but des experts des sciences sportives est de fournir aux entraîneurs et médecins des informations fiables sur la technique des athlètes. Le manque de méthodes permettant l'évaluation des athlètes sur le terrain ainsi que l'estimation précise des efforts articulaires représente, à ce jour, une limitation majeure pour atteindre ces objectifs. Les travaux effectués dans la thèse vise à contribuer au développement des ces méthodes. Deux approches complémentaires ont été adoptées: une Approche à Basse Résolution - relative à l'évaluation de la performance - où l'utilisation de capteurs inertiels portables est exploitée au cours des différentes phases de la course de vitesse, et une Approche à Haute Résolution - lié à l'estimation des efforts articulaires pour la prévention des blessures - où des contraintes personnalisées pour la modélisation cinématique du genou dans le contexte des techniques d'optimisation multi-corps ont été définies. Les résultats obtenus par l'Approche à Basse Résolution indiquent que, en raison de leur portabilité et leur faible coût, les capteurs inertiels sont une alternative valable aux instrumentations de laboratoire pour l'évaluation de la performance pendant la course de vitesse. En utilisant les données d'accélération et de vitesse angulaire, l'inclinaison et la vitesse angulaire du tronc, la vitesse horizontale instantanée et le déplacement du centre de masse, ainsi que la durée de la phase d'appui et du pas ont été estimés. En ce qui concerne l'Approche à Haute Résolution, les résultats ont montré que les longueurs du ligament antérieur croisé et du latéral externe diminuaient, alors que celle du faisceau profond du ligament latéral interne augmentait de manière significative lors de la flexion. Les variations de longueur du ligament croisé postérieur et du faisceau superficiel du ligament latéral médial étaient de l'ordre de l'indétermination expérimentale. Un modèle mathématique a été fourni qui a permis l'estimation des longueurs ligamentaires personnalisées en fonction de la flexion du genou et qui peuvent être intégrées dans une procédure d'optimisation multi-corps.

Cette thèse porte sur la conception et la réalisation d’une nouvelle expérience d’interféromètre atomique au SYRTE. Elle permettra de réaliser des mesures ultrasensibles du gradient vertical de gravité. Cette expérience fonctionnera à terme en utilisant comme source des atomes ultra-froids, préparés sur une puce à atomes. Elle utilisera comme séparatrices des transitions multiphotoniques, obtenues par diffraction de Bragg d’ordre élevé. Le transport des atomes sera assuré par des réseaux optiques en mouvement. Une première partie du dispositif expérimental a été assemblée et son fonctionnement a été validé en réalisant un interféromètre dual. Cet interféromètre est réalisé sur deux ensembles d’atomes produits successivement à partir de la même source d’atomes froids, et interrogés par une même paire de faisceaux Raman. Une nouvelle méthode d’extraction de la phase différentielle a été démontrée expérimentalement. Elle repose sur l’exploitation des corrélations entre les mesures de phase des interféromètres et une estimation de la phase sismique fournie par la mesure annexe d’un capteur classique. / This thesis is about the design and realisation of a new atomic interferometer experiment at SYRTE. It will allow ultra-sensitive measurements of the vertical gradient of gravity. This experiment will work using ultra-cold atoms as a source, prepared on an atom chip. It will use large momentum transfer beam-splitter, obtained by high order Bragg diffraction. The transport of atoms will be provided by moving optical lattices. A first part of the experimental setup was assembled and its operation was validated by producing a dual interferometer. This interferometer is performed on two atomic clouds produced successively from the same source of cold atoms, and interrogated by the same pair of Raman beams. A new method of differential phase extraction has been experimentally demonstrated. It is based on the exploitation of the correlations between the interferometer phase measurements and the estimation of the seismic phase provided by an additional classical sensor.