Directional microphones, which suppress noise coming from unwanted directions while preserving sound signals arriving from a desired direction, are essential to hearing aid technology. The device presented in this paper abandons the principles of standard pressure sensor microphones, dual port microphones, and multi-chip array systems and instead employs a new method of operation. The proposed device uses a lightweight silicon micromachined structure that becomes “entrained” in the oscillatory motion of air vibrations, and thus maintains the vector component of the air velocity. The mechanical structures are made as compliant as possible so that the motion of the diaphragm directly replicates the motion of the sound wave as it travels through air. The microphone discussed in this paper achieves the bi-directionality seen in a ribbon microphone but is built using standard semiconductor fabrication techniques and utilizes piezoelectric readout of a circular diaphragm suspended on compliant silicon springs. Finite element analysis and lumped element modeling have been performed to aid in structural design and device verification. The proposed microphone was successfully fabricated in a cleanroom facility at The University of Texas at Austin. Testing procedures verified that the resonant frequency of the microphone, as expected, was much lower than in traditional microphones. This report discusses the theory, modeling, fabrication and testing of the microphone. / text

The objective of this research is to study different novel developed techniques for spacecraft attitude determination methods using star tracker sensors. This dissertation addresses various issues on developing improved star tracker software, presents new approaches for better performance of star trackers, and considers applications to realize high precision attitude estimates. Star-sensors are often included in a spacecraft attitude-system instrument suite, where high accuracy pointing capability is required. Novel methods for image processing, camera parameters ground calibration, autonomous star pattern recognition, and recursive star identification are researched and implemented to achieve high accuracy and a high frame rate star tracker that can be used for many space missions. This dissertation presents the methods and algorithms implemented for the one Field of View 'FOV' StarNavI sensor that was tested aboard the STS-107 mission in spring 2003 and the two fields of view StarNavII sensor for the EO-3 spacecraft scheduled for launch in 2007. The results of this research enable advances in spacecraft attitude determination based upon real time star sensing and pattern recognition. Building upon recent developments in image processing, pattern recognition algorithms, focal plane detectors, electro-optics, and microprocessors, the star tracker concept utilized in this research has the following key objectives for spacecraft of the future: lower cost, lower mass and smaller volume, increased robustness to environment-induced aging and instrument response variations, increased adaptability and autonomy via recursive self-calibration and health-monitoring on-orbit. Many of these attributes are consequences of improved algorithms that are derived in this dissertation.

As wireless devices are becoming more powerful, more flexible and less costly to produce, they are often being applied in new ways. Combining wireless technology with new types of sensors results in the ability to monitor and control the environment in ways not previously possible. For example, an intelligent wireless sensor system that consists of a sensor, digital processor and a transceiver can be mounted on a board the size of a coin. The data collected by these devices are then transmitted to a central unit which is able to thoroughly process and store this data. Not only can the central processing station provide reports about certain physical parameters in the environment, it can also control the environment and other parameters of interest. The design process of these wireless sensor platforms is a well-developed area of research that covers concepts like networking, circuit design, Radio-Frequency (RF) circuits and antenna design. The design of a wireless sensor can be as simple as putting together a microcontroller, a transceiver and a sensor chip or as complicated as implementing all the necessary circuitry into a single integrated circuit. One of the main applications of the sensors is in a control loop which controls physical characteristics in an environment. Specifically, if the objective of a control system is to limit the amount of vibrations in a structure, vibration sensors such as accelerometers are usually used. In environments where the use of wires is costly or impossible, it makes sense to use wireless accelerometers instead. Among the numerous applications that can use such devices are the automotive and medical vibration control systems. In the automotive industry it is desirable to reduce the amount of vibrations in the vehicle felt by the passengers. These vibrations can originate from the engine or the uneven road, but they are damped using passive mechanical elements like rubber, springs and shocks. It is possible however, to have a more effective vibration suppression using active sensor-actuator systems. Since adding and maintaining wires in a vehicle is costly, a wireless accelerometer can be put to good use there. A medical application for wireless accelerometers can be used with a procedure called Deep Brain Stimulation (DBS). DBS is a relatively new and very effective treatment for advanced Parkinson’s disease. The purpose of DBS is to reduce tremors in the patients. In DBS a set of voltages is applied to the brain of the patient as some optimum combinations of voltages will have a very positive effect on the tremors. Those optimum voltages are currently found by trial and error while a doctor is observing the patient for tremors. Wireless accelerometers with the use of a computer algorithm can assist in this process by finding the optimum voltages using the feedback provided by the accelerometers. The algorithm will assist the doctor in making decisions and has the potential of finding the optimums completely on its own.

Interlocking Concrete Pavements also known as block pavements are one of the integral parts of the pavement system in Europe. The use of ICP slowly extended to other countries including North America. As the usage increased the need for more scientific research was developed which resulted in the study of ICP design and analysis methods, construction practices and materials specifications. This thesis presents a research project involving the design, construction, instrumentation, performance modeling and other field tests of eight ICP crosswalks with four different design assemblies. The research projects were constructed at the Centre for Pavement and Transportation Technology (CPATT) Test Track and at the University of Waterloo Ring Road. Each of the test sections is instrumented with structural and environmental sensors of sensors to monitor the pavement performance under heavy truck traffic, typical municipal loadings and to quantify environmental effects. A database is generated and the measured stress, strain, temperature and moisture measurements are analysed to evaluate the expected long-term performance of the structural components of ICP crosswalk designs.

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Despite a recent focus on understanding cumulative load, researchers still prefer to analyze the data using mean and peak values. At the same time, technological advancements have provided biomechanists with methods of collecting large amounts of data pertaining to joint loading. Waveform analysis offers another option that will become increasingly relevant, as wireless data collection devices become common place and provide access to waveforms from many hours of recording. The overall objectives of this research were to demonstrate some of the limits of current methods of biomechanical analysis, and introduce an alternative, and secondly, to propose a wireless system for use in field-based studies. An exploratory study using Functional Data Analysis (FDA) was completed on experimental lifting data. The results demonstrated that FDA can elucidate subtle differences in the curve shape outside of the peak areas typically used for statistical analysis that were attributed to fatigue. These findings support the need for a better understanding of how workers change their movement strategies as time progresses throughout the length of the workshift. To achieve this type of knowledge, a wireless data collection device utilizing inertial motion sensors (IMS) was introduced and validated for field use in the remaining three chapters. The IMS units in conjunction with an anthropometric model were tested against a traditional link segment model recorded in a gold-standard, video system. Testing that occurred in the entire reach space volume yielded errors as low as 5% for the lumbar moment, but errors also greatly exceeded 50% RMS error in some cases. Three hand switch alternatives were tested for their potential to provide external hand force timing and duration information to the link segment model, but none were found to be perfectly suitable in the current configuration. In conclusion, a wireless system based on IMS units has the potential to provide long-term data collection, but the development of the calibration routines and complexity of the underlying model must be improved. FDA was shown to have good potential for identifying subtle differences in curve shapes, and may become useful when long-term field-based data are readily available with the proposed IMS system. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2009-04-21 09:01:22.968

Microgyroscopes find popular applications in modern life, such as, vehicle navigation, inertial positioning, human body motion monitoring, etc. In this study, three unique MEMS gyroscopic sensors were investigated using experimental methods and finite element analysis (FEA) modelling, particularly their modal behaviour. The analytical, simulated and experimental results were compared and the discrepancy between resonant frequencies of the significant mode shapes was discussed. Three microfabricated gyroscopes were investigated: a thermally-actuated in-plane gyroscope, an electrostatically-actuated in-plane gyroscope and an electrostatically-actuated out-of-plane gyroscope. Numerical finite element modal analysis for these three gyroscopes was conducted using COMSOL Multiphysics. The experimental testing was conducted using a microsystem analyzer (MSA-400 PolyTec) with an integrated laser vibrometer. The simulation models predicted that the frequencies for driving and sensing modes were 4.948kHz and 5.459kHz for a thermally-actuated gyroscope, which agreed well with experimentally determined results of 5.98kHz and 6.0kHz respectively. The power requirements of a thermally-actuated gyroscope were 363.39mW to elicit a maximum peak-to-peak displacement of 4.2μm during dynamic operation. Similarly, the simulated frequencies for the driving and sensing modes were 1.170kHz and 1.644kHz for an electrostatically-actuated in-plane gyroscope, which corresponded to experimentally determined resonant frequencies 1.6kHz and 1.9kHz. Simulation for the electrostatically-actuated out-of-plane gyroscope was conducted and the frequencies for the driving and sensing modes were found to be 2.159kHz and 3.298kHz. Due to some fabrication defects, the experimental testing for this microgyroscope was not successful. Some recommendations to improve the design were provided for the future work. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-06-02 22:00:52.994

This thesis is an investigation of possible applications for a low cost non-contact magnetic rotational position sensor. A single stage gearbox operating spur gears was instrumented with these sensors along with typical optical encoders. These rotational position devices were used independently to measure gearbox Transmission Error (TE) during operation. Basic filtering techniques were used to condition the TE so that localized faults were observable. Characteristic feature extraction on the TE using RMS, Kurtosis and Crest Factor was used to quantify gearbox dynamics. These features were able to measure dynamic changes in gearbox health, such as wearing in the gears or the progression of a fault resulting in full tooth failure. These sensor attributes are ideal for machine condition monitoring applications where catastrophic failure can be forewarned by incipient fault detection. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-10-12 17:21:13.125

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In this thesis, investigations into fabricating tin oxide hydrogen gas sensors from films assembled by the deposition of tin clusters are reported. The tin clusters were formed in a UHV compatible cluster apparatus by DC magnetron sputtering and inert gas aggregation. Through SEM imaging, it was found that the morphology of tin cluster assembled films deposited onto silicon nitride substrates was highly coalesced. The coalescence between the clusters was significantly reduced by reacting the clusters with nitrogen before they were deposited. This resulted in granular films with a grain size close to that of the deposited clusters. The coalesced and granular tin films were used to fabricate tin oxide conducti-metric gas sensors. This was done by depositing the tin films onto gold contacts and then oxidising them by baking them at 250°C for 24 hours. The sensors were tested using a purpose built gas test rig. It was found that the sensors with the granular film morphology were much more sensitive to 500 ppm, 1000 ppm, and 5000 ppm of hydrogen at 200°C in ambient air with zero humidity. This was attributed to the smaller grain size and the larger surface area of the granular films.