Dissertations / Theses on the topic 'Dynamic pressure sensor'

Pressure measurements are required in various industrial applications, including extremely harsh environments such as turbine engines, power plants and material-processing systems. Conventional sensors are often difficult to apply due to the high temperatures, highly corrosive agents or electromagnetic interference (EMI) noise that may be present in those environments. Fiber optic pressure sensors have been developed for years and proved themselves successfully in such harsh environments. Especially, diaphragm based fiber optic pressure sensors have been shown to possess advantages of high sensitivity, wide bandwidth, high operation temperature, immunity to EMI, lightweight and long life. Static and dynamic pressure measurements at various locations of a gas turbine engine are highly desirable to improve its operation and reliability. However, the operating environment, in which temperatures may exceed 600 °C and pressures may reach 100 psi (690 kPa) with about 1 psi (6.9kPa) variation, is a great challenge to currently available sensors. To meet these requirements, a novel type of fiber optic engine pressure sensor has been developed. This pressure sensor functions as a diaphragm based extrinsic Fabry-Pérot interferometric sensor. One of the unique features of this sensor is the all silica structure, allowing a much higher operating temperature to be achieved with an extremely low temperature dependence. In addition, the flexible nature of the sensor design such as wide sensitivity selection, and passive or adaptive temperature compensation, makes the sensor suitable for a variety of applications An automatically controlled CO2 laser-based sensor fabrication system was developed and implemented. Several novel bonding methods were proposed and investigated to improve the sensor mechanical ruggedness and reduce its temperature dependence. An engine sensor testing system was designed and instrumented. The system generates known static and dynamic pressures in a temperature-controlled environment, which was used to calibrate the sensor. Several sensor signal demodulation schemes were used for different testing purposes including a white-light interferometry system, a tunable laser based component test system (CTS), and a self-calibrated interferometric-intensity based (SCIIB) system. All of these sensor systems are immune to light source power fluctuations, which offer high reliability and stability. The fiber optic pressure sensor was tested in a F-109 turbofan engine. The testing results prove the sensor performance and the packaging ruggedization. Preliminary laboratory and field test results have shown great potential to meet not only the needs for reliable and precise pressure measurement of turbine engines but also for any other pressure measurements especially requiring high bandwidth and high temperature capability.
Ph. D.

The aim of this study was to further understand the fouling and cleaning mechanisms of synthetic membranes used to filter an industrially relevant feed. The main focus of this study was to understand the fouling layer properties during pressure driven filtration. A relatively new technique known as Fluid Dynamic Gauging (FDG) was applied to examine the fouling layer thickness. This work comprised of four main themes with overlapping objectives: (i) the optimisation of Spent Sulphite Liquor fouling and cleaning conditions, (ii) the optimisation of molasses fouling and cleaning conditions, (iii) the investigation of the effect of a simple pre-treatment upon the membrane separation performance, and (iv) the application of the FDG in the study of polymeric membranes. An understanding of the mechanisms involved in fouling and cleaning of microfiltration and ultrafiltration membranes used to filter molasses and SSL has been attained. The variables affecting permeate flux and quality were optimised and mechanistic information concerning the synergistic effects between fouling and cleaning was gathered. The application of a simple NaOH pre-treatment was found to affect both the type of foulant species attaching to the membrane surface, and resulted in an altered separation and cleaning performance. Zeta potential measurements, FTIR and AFM demonstrated that both in-pore and surface fouling was present. The data collected indicated that for both membranes evaluated, different fouling species were found to have attached, depending upon the pre-treatment protocol used. These findings are significant, as they offer support to the recommendations made by some polymeric membrane manufacturers that conditioning protocols should include a NaOH step. However, in the SSL system examined, the effect of NaOH pre-treatment resulted in an improvement in the subsequent performance only over the first two or three complete filtration cycles. It is therefore necessary to study membrane systems over multiple fouling and cleaning cycles before a recommendation can be made. An improved understanding of the interaction between the surface chemistry and surface physics during membrane filtration of complex food based material will benefit both membrane manufactures and food industry based users. The technique of Fluid Dynamic Gauging was incorporated into an existing system and validated to monitor the development of cake layers over time. The FDG was also used to optimise conditions and track the thickness of the cake layer during multiple fouling cycles and its removal rate during cleaning, as an aid to understanding removal mechanisms. It has been shown that operating conditions have to be carefully chosen to minimise the effect of membrane fouling. The results show that FDG is a versatile and powerful technique for characterising the dynamics and mechanical behaviour of fouling layers on membrane surfaces. A particular advantage of the FDG technique is its ability to determine the thickness of fouling layers where other techniques would find difficulty. For example, the layers formed in this study were opaque, and consequently the determination of the development of deposit thickness with time would have been very challenging using conventional optical microscopy techniques.

This report describes a simple mechanical system developed for producing dynamic pressures of up to 50 kPa from zero-to-peak and over the frequency range 0-58 Hz. The system is constructed for dynamic calibration of pressure sensors and consists of an open tube, 30 cm in height, mounted vertically on the support plate. The support plate is connected to the vibration exciter which is driven by a piston, a connecting rod, disc and axle, and an electric motor. The pressure  sensor to be calibrated is mounted vertically at the bottom of the open tube so that the diaphragm of the sensor is in contact with the working liquid in the tube. When the system is started, the motion of the piston provides a sinusoidal movement to the open tube and calibration is achieved. The different parts of the system are designed using NX Siemens. MatLab is used to determine the results and graphs from the equations derived. The analysis shows that the displacement, velocity, and acceleration of the system are highly affected by the distance between the disc centre and the disc pin, and the rotational speed of the system. The length of the connecting rod does not affect the displacement and barely affects the velocity and acceleration of the system. The total force, torque, and power of the system is utilized to select the electric motor and the frequency inverter.
Denna rapport beskriver ett enkelt mekaniskt system som utvecklas för att producera dynamiska tryck upp till 50 kPa från noll-till-topp och över frekvensområdet 0-58 Hz. Systemet är konstruerat för dynamisk kalibrering av trycksensor och består av öppet rör 30 cm höjd monteras vertikalt på stödplattan. Stödplattan är ansluten till vibrationsexcite dvs, den yttre cylindern som drivs av en kolv, en vevstake, skiva och axel och en elmotor. Trycksensorn som skall kalibreras är monterad vertikalt vid botten av det öppna röret så att membranet hos sensorn är i kontakt med arbetsvätskan i röret. När systemet startas, ger rörelsen hos kolven som ger vibrationer till det öppna röret och kalibrering uppnås. De olika delarna av systemet är utformade med hjälp av NX Siemens. MatLab används för att bestämma resultaten och diagram härledda från ekvationerna. Analysen visar att den förskjutning, hastighet och acceleration av systemet är i hög grad påverkade av avståndet mellan skivans centrum och skivtappen, och rotationshastigheten hos systemet. Längdn av vevstaken påverkar inte försjutningen och påverkar knappt hastigheten och accelerationen hos systemet. Den totala kraften, vridmomentet och kraften i systemet användes för attvälja de andra komponenterna i systemet dvs, den elektriska motorn och frekvensomvandlaren.

Coal mine impoundment failures have been well documented to occur due to an increase in excess pore pressure from sustained monotonic loads. Very few failures have ever occurred from dynamic loading events, such as earthquakes, and research has been done regarding the stability of these impoundment structures under such natural seismic loading events. To date no failures or damage have been reported from dynamic loading events caused by near-by production blasting, however little research has been done considering these conditions. Taking into account that current environmental restrictions oblige to increase the capacity of coal impoundments, thus increasing the hazard of such structures, it is necessary to evaluate the effects of near-by blasting on the stability of the impoundment structures. To study the behavior of excess pore pressure under blasting conditions, scaled simulations of blasting events were set inside a controlled sand tank. Simulated blasts were duplicated in both saturated and unsaturated conditions. Explosive charges were detonated within the sand tank at various distances to simulate different scaled distances. Information was collected from geophones for dry and saturated scenarios and additionally from pressure sensors under saturated conditions to assess the behavior of the material under blasting conditions.

Le travail realise durant cette these a consiste en le developpement, la realisation et les tests de deux instruments destines a l'etude des environnements neutres et ionises planetaires et cometaires. Le premier instrument, idm (ion dynamics monitor), est un spectrometre a plasma thermique et suprathermique (< 200 ev) developpe initialement lors de la phase de consolidation du projet cometaire europeen rosetta. Une version amelioree a ensuite ete adaptee pour l'etude de l'ionosphere et de la couche limite de mars dans le cadre du projet dynamo. Les deux versions du spectrometre ont ete testees en laboratoire et les resultats, en tres bon accord avec la simulation, ont montre le respect des specifications necessaires a la mesure. Le second instrument est destine a la mesure des parametres dynamiques d'une atmosphere neutre. Une etude detaillee des techniques de mesures actuelles de la dynamique d'un gaz neutre est tout d'abord presentee et montre l'interet de l'utilisation d'un concept instrumental reposant sur des jauges de densite a impact electronique et des chambres d'equilibre. L'instrument cops (comet pressure sensor), premiere realisation de ce concept, sera embarque a bord de la sonde rosetta et permettra l'evaluation de la vitesse d'expansion et de la densite du gaz cometaire. Le developpement de l'instrument a necessite la mise au point de techniques de modelisation de l'interaction d'un gaz et d'un solide en regime moleculaire et a conduit a la realisation de tests sous faisceau moleculaire. Les resultats montrent que les principaux objectifs sont atteints. Une seconde application de ce concept instrumental destinee a l'etude de la haute atmosphere martienne est aussi presentee.

La perception de la flaveur des aliments dépend de la perception de plusieurs composés en mélange dans des proportions équilibrées. Interactions perceptives entre différents odorants ainsi que la libération dynamique des odorants par la matrice alimentaire sont les principaux facteurs qui influencent la perception globale. L’objectif de cette thèse de doctorat était d’étudier la perception du mélange d’odorants qui constituent l’arôme du fromage à pâte pressée, en prenant en compte les interactions perceptives et la dynamique de libération des composés par la matrice. Une stratégie, comprenant une caractérisation complète des odorants des fromages, suivie d’une recombinaison qualitative et d’une étude détaillée des rôles respectifs des composés clés, et finalement la prise en compte de la dynamique de libération par incorporation des composés dans une matrice fromagère, a été appliquée. Des caractérisations approfondies sensorielles et instrumentales nous ont permis de mettre en évidence des relations entre la perception sensorielle et la composition des composés volatils et proposer des hypothèses. La recombinaison des différents composés a été testée afin d’étudier le rôle de chacun en mélange. Aidés par des apprentis aromaticiens durant la phase des recombinaisons nous avons pu observer particulièrement que 12 composés étaient très importants pour l’odeur du fromage. Par la suite nous avons étudié des interactions entre odeurs en appliquant des techniques de stimulation odorante en phase gazeuse, puis la dynamique de libération des composés en incorporant l’arôme dans une matrice fromagère par des techniques permettant de mesurer la quantité libérée en fonction du temps
Perception of the aroma of food products depends both the chemical composition of food and human neurophysiology. The perception of food flavour, including cheese often relies on the perception of several aroma compounds in mixture in balanced proportions. Perceptual interactions among aroma compounds in mixtures and also the release of aroma compounds from the food product are the main factors that influence the global perceived aroma of food. Hence, the objective of this PhD study was to investigate the mixture of aroma compounds representing the aroma of semi-hard cheese by taking into account perceptual interactions among odorants and the dynamic release of the compounds by the cheese matrix. A strategy involving a complete characterisation of the cheeses followed by a recombination and investigation of the role of the key-aroma compounds and the dynamic release of the aroma compounds from the cheese matrix was taken into account. Comparison of the sensory and instrumental characteristics was made in order to highlight relationships between sensory perception of the aroma and the volatile composition of the cheeses and thus point out the molecular origins of the perceived cheese aroma. Recombination of selected aroma compounds was tested, in order to study the role of each aroma compound within the mixture. Especially 12 compounds seemed important for the semi-hard cheese aroma. To investigate the odour-odour interactions, different odour-stimulation tools were applied and dynamic release of aroma compounds was taken into account by incorporating the aroma compounds into a cheese matrix by different techniques allowing measuring the quantities released as function of time

碩士
國立中興大學
精密工程學系所
102
In this paper reports a novel full-range vacuum sensing device, capable of exceeding the sensing range of most gauges and reducing the volume by a factor of 10. The device gauges the free decay rate of a micro-cantilever beam which provides uniform in-plane stress across the surface of the beam, and a thick square plate connected to the trapezoid beam deflected using Piezoelectric Thin-Film Pb(Zr,Ti)O3(PZT) used to determine the free decay rate of the sensing beam with respect to deflection force and vacuum pressure. In the beginning,the paddle cantilever vibrated by the piezoelectric actuators, and then the decay rate of the deflected beam in vacuum environment was measured by piezoelectric sensor. We found that the free decay rate of the deflected beam is linearly proportional to the vacuum pressure. This rapid response in pressure ranges demonstrates that the device has high degree of sensitivity. The proposed device represents a considerable advancement in the development of miniature full-range pressure gauges as well as the applicability of micro-electromechanical systems.

Tese de doutoramento em Ciências - Física
The present work relates to the development of a sensors network for mapping the pressure fields at the externa! prosthesis socket/stump interface, in particular at lower limbs. The project consists on the design and implementation of a sensor array from piezoresistive polymer based materiais to measure quasi-static and dynamic deformations. The sensors were prepared from poly(vinylidene fluoride) - PVDF and epoxy nanocomposites with carbon nanotubes or nanofibres. The development of thin film-based stretchable electrodes was carried out using the GLancing Angle Deposition, GLAD, technique. A specific electronic circuit for signal processing was used with a wireless data acquisition system. Finally, a prototype was designed , constructed and tested in four IO\.ver limb amputees, in laboratory conditions , under different types of solicitations at the Vocational Rehabilitation Center - CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). The piezoresistive-based sensors were developed using two different approaches; a) nanocomposites composed of poly(vinylidene~ fluoride) filled with carbon nanotubes (CNT/PVDF); and b) epoxy resins filled with carbon nanotubes or nanofibres (CNT/EPOXY). The PVDF samples were prepared by hot pressing and spray printing with CNT sample concentrations up to loadings of 1 O wt.%. The phase present in the composites CNT/PVDF was the alfa-phase. Due to the fact that externa! limb prostheses must sustain cyclic loading and unloading during normal walking conditions, the correlation between the electrical resisitivity and mechanical solicitations was obtained for differents mechanical solicitations, including variations in deformation , temperature and velocity. ln relation to CNT/EPOXY, the electrical response is linear over a wide strain range and the values of the maximum gauge factor is ~2 . 8 . The stability of the signal over 32 cycles, the time response to deformatoins from 0.1 to 50 mm min- 1 and the stable temperature behaviour up to 60 °C shows the viability of these materiais to be used as piezoresistive sensors. ln the sarne way, the electrical and piezoresistive response of CNT/PVDF composites has been studied. The piezoresistive response, quantitatively analysed by the gauge factor, is maximized at concentrations around the percolation threshold, around 2 wt.% loading, and the maximum value of the gauge factor is ~6.2. The piezoresistive response is stable with the number of cycles and reversible up to temperatures below 100 °C. The linearity of the response over a wide strain range shows the viability of these materiais to be used as piezoresistive sensors. The development of stretchable electrodes was carried out using columnar Ti-Ag thin films with a Ag content of 8 at.% prepared by D.C. magnetron sputtering on CNT/PVDF piezoresistive composites. The Ti-Ag system was chosen to coat the polymers due to some important points related to its characteristics. First of ali, Ti-Ag thin films combine the excellent biocompatibility of Ti with the Ag antimicrobial properties, offering also good thermal, electrical , chemical and mechanical properties, together with good wear and corrosion resistance. Secondly, the addition of Ag was also thought in order to tailor the elasticity of the Ti films, allowing a better response of the coated polymer under any particular deformation or stretching of the composite sensor when in-service. Additionally, the deposition of the films by GLancing Angel Deposition , GLAD, instead of conventional Magnetron Sputtering Deposition , MSD, was also carried to allow and even extend this elasticity resistance. ln fact, by depositing films with some particular architectures , inclined, zigzag, etc., there is a real possibility to deposit thin films with extended capacities to resist to stretching or any common deformation that a polymeric-based sensor induce when in-service. Furthermore, there is also the possibility to improve the electrical response of the system and this, ali together, to improve the response and the adequacy of the ali sensor arrangement in this particular type of applications . By changing the typical columnar growth microstructure, obtained by conventional sputtering, the goal was to tune the mechanical and electrical responses of the materiais. Upon uniaxial stretching of the prepared zigzag thin films, the resistance of the thin film starts increasing smoothly for strains up to 3%. Above 10% strain a sharp increase of the electrical resistance is observed due to film mechanical failure and therefore interruption of the electrical conductivity pathways. The best results were obtained when the polymer was coated with intermediate incident angles (a = 60°). The results show that the electrodes structure has a pronounced influence on the overall sensor response leading to values of the GF up to 85 mainly due to the electromechanical contribution of the thin film, which stability has to be studied for potential use for sensor applications itself. Human study was conducted at the Vocational Rehabilitation Center- CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). The subjects transfemoral (TF) and transtibial (TI) amputees , walked for 2 minutes in a crosswalk at a relatively comfortable speed of 0.33 m/s. During this time it was possible to simulate a normal walk of approximately 40 m and the results provided good indications that it is possible to identify areas of criticai pressure. Thus, it is expected that the present method will become helpful for comprehensively evaluating the biomechanical conditions of the residual limb and prosthesis interface. The system developed in this project may allow monitoring of the process of rehabilitation with a new prosthesis and will support clinical decisions in relation to the potential effects of modifications on the socket, when adjustments are required.
O presente trabalho descreve o desenvolvimento de uma matriz de sensores para mapear as pressão exercidas em próteses externas dos membros inferiores, na interface coto/prótese, baseados em materiais piezoresistivos para medir as deformações dinâmicas e quasi-estáticas . Os sensores foram preparados a partir de nanocompósitos de poli(fluoreto de vinilideno) - PVDF e resinas epoxy com nanotubos- CNT ou nanofibras- CNF de carbono. Adicionalmente, foram desenvolvidos elétrodos estiráveis baseados em filmes finos através da técnica de pulverização catódica GLAD, Glancing Angle Deposition. O circuito electrónico usado para o processamento de sinal foi desenvolvido com um sistema de aquisição de dados sem fios. Finalmente, foi construído um protótipo que foi testado em quatro pacientes amputados dos membros inferiores em condições de laboratório, sob diferentes tipos de solicitações no centro de reabilitação vocacional - CRPG (Centro de Reabilitação Profissional de Vila Nova de Gaia). Com base no efeito piezoresistivo , os sensores foram obtidos usando duas diferentes ... abordagens; a) compósitos de poli(fluoreto de vinilideno) com nanotubos de carbono (CNT/PVDF); e b) compósitos de resinas epóxi com nanotubos de carbono ou nanofibras (CNT/epóxi). As amostras de PVDF foram preparadas por prensagem a quente e/ou por spray com concentrações de CNT até 10 % em peso. A fase cristalina presente nos compósitos CNT/PVDF foi a fase alfa-PVDF. Foi obtida a correlação entre a resistividade elétrica e as diferentes solicitações mecânicas, através da deformação , da variação da temperatura, da velocidade e do tempo de resposta do compósito. Em relação aos compósitos de CNT/epóxi, obteve-se uma resposta elétrica linear e os valores de sensibilidade máxima (gauge factor) foram de ~ 2.8. Através das diferentes solicitações mecânicas , a estabilidade do sinal para mais de 32 ciclos, o tempo de resposta para deformações de 0.1 a 50 mm min· 1 e a estabilidade com a temperatura até 60 oc mostram a viabilidade destes materiais para serem utilizados como sensores piezoresistivos. Da mesma forma , a resposta elétrica e piezoresistiva dos compósitos de CNT/PVDF foi estudada. A resposta piezoresisitiva foi quantitativamente analisada pela sensibilidade do material (gauge factor) e verificou-se que é máxima para concentrações em tomo do limiar de percolação, ~2 % de CNT em peso, e o valor máximo obtido foi de ~ 6.2. A resposta piezoresistiva é estável em função do número de ciclos e reversível até temperaturas inferiores a 100 °C. A linearidade da resposta com a deformação mostra a viabilidade destes materiais para serem utilizados como sensores piezoresistivos. O desenvolvimento de elétrodos estiráveis foi realizado usando filmes finos com estrutura colunar de titânio e prata - Ti-Ag com um teor de Ag de 8 at.% preparados por pulverização catódica em compósitos piezoresistivos de CNT/PVDF. O sistema Ti-Ag foi escolhido para revestir os polímeros devido a alguns pontos importantes relacionados com as suas características. Primeiro de tudo , filmes finos de Ti-Ag combinam a excelente biocompatibilidade do titânio com as propriedades anti-microbianas da prata, oferecendo deste modo boas propriedades químicas, mecânicas e elétricas, juntamente com boas propriedades de resistência ao desgaste e corrosão. Segundo, a adição de prata também foi incluída com o objetivo de promover a elasticidade do filme de modo a permitir uma melhor adaptação do filme ao polímero. Por outro lado, o sistema GLAD teve por grande objetivo este mesmo propósito: melhorar a resposta elétrica e a elasticidade do sistema de modo a permitir uma melhor adequação à deposição dos elétrodos em materiais flexíveis. A técnica de GLAD foi usada para alterar a microestrutura típica de crescimento colunar obtida por pulverização catódica convencional , Magnetron Sputtering Deposition, MSD, em diferentes arquiteturas de crescimento , tais como colunas inclinadas e em ziguezague, a fim de ajustar as respostas meéânicas e elétricas dos materiais. Após estiramento uniaxial dos filmes finos em ziguezague, a resistência eléctrica do filme fino começa a aumentar tenuemente para tensões até 3%. Acima de 10% de estiramento dá-se um aumento acentuado da resistência eléctrica que é observado devido à falha mecânica do filme . Os melhores resultados foram obtidos quando o polímero foi revestido com filmes depositados com ângulos incidentes intermédios (a = 60 °). Os resultados mostram que a estrutura dos elétrodos tem uma acentuada influência sobre a resposta global do sensor levando a valores de sensibilidade até 85. Esta contribuição deve-se essencialmente à contribuição eletromecânica do filme fino. O estudo com Pacientes foi realizado no centro de reabilitação profissional- CRPG (Centro de Reabilitação Profissional de Gaia), com amputados transfemoral (TF) e amputados transtibial (TT), que caminharam durante 2 minutos numa passadeira eléctrica com uma velocidade relativamente confortável de 0,33 rn/s. Durante este tempo , foi possível simular uma marcha normal de aproximadamente 40m. Deste modo demonstrou-se que é possível identificar as áreas criticas de pressão. Espera-se que, o presente método, se tome útil para avaliar exaustivamente as interações biomecânicas entre o membro amputado e a prótese. O sistema desenvolvido neste projeto poderá permitir o monitoramento durante o processo de reabilitação e apoiar em decisões clínicas em relação aos potenciais efeitos e modificações do encaixe da prótese no coto .
Fundação para a Ciência e a Tecnologia (FCT) for the financial support (SFRH/BD/69796/2010).

Piezoelectric technology based dynamic pressure sensors are widely used for the measurement of rapid pressure variations with respect to time. Quartz is the piezoelectric material ruling the dynamic pressure sensor industry even now. Though researches are happening in the area of piezoelectric materials, they are not further taken up to device level. A complete understanding of these new materials and features of the devices developed by utilising them will be a supporting factor to take up their commercial application. In this work, an earnest attempt is made to bridge the gap between the laboratory and commercialisation. ZnO is one of the piezoelectric materials with promising features to meet future world’s requirement. In the last few years, extensive investigations had been performed regarding the synthesis of thin film and nanostructures of ZnO. However, a comprehensive study on their device application is not available in the literature. The present research work focuses on the optimisation of the fabrication processes and experimental evaluation of the packaged dynamic sensors realised using ZnO thin film and nanowire array. An exhaustive literature survey has been conducted to study the properties of various piezoelectric materials, substrate materials, different thin film deposition methods, Nanowire synthesis methods and characterisation methods used for evaluation of dynamic pressure sensors. ZnO thin films were fabricated using RF reactive magnetron sputtering for four different thicknesses by varying deposition duration and characterisation of these films were conducted to study their crystal structure, morphology & chemical composition. These films were packaged as dynamic pressure sensors and were experimentally evaluated for their suitability for dynamic pressure sensing applications. Based on the test results, most optimised sensor was determined from these four versions. A similar approach was followed to study the suitability of ZnO nanowire array for dynamic pressure sensing application. ZnO nanowire array was synthesised using hydrothermal method, characterised for its material properties and the as-synthesised nanowire array was evaluated for dynamic pressure sensing application after packaging. Both thin film and nanowire array of ZnO exhibited encouraging results when packaged and tested as dynamic pressure sensor. Dynamic pressure sensors realised using ZnO thin film are on par with the commercially available dynamic pressure sensors. ZnO nanowire array based sensor also showed promising results. This research work concludes that ZnO, in its thin film and nanowire form, is highly suitable for the development of dynamic pressure sensors and recommends its commercial deployment.

碩士
國立臺北科技大學
機電整合研究所
96
While most studies on hydraulic systems focus mainly on their static characteristic, a good understanding of their dynamic characteristic is of equally important. Pressure sensors are used in complex dynamic working environment. There are some problems in high precise system, for example, slower response speed, lacking of smoothly working, vibration and fatigue. For the reason of not catching dynamic characteristic of sensors, the performance and life of sensors will be decreased. Using a self-developed square pressure wave generator(SPWG),this study explores the dynamic characteristic of pressure sensors in hydraulic systems using system identifications analysis. As a replacement of the traditional directional control valve, the developed SPWG can achieve high-frequency switching by the difference method between the revolving shaft and fixed ring. The square pressure waves generated serve as inputs into the hydraulic system. With the high-sensitivity piezoelectric pressure sensor as the reference sensor, tests are conducted concurrently using a piezoelectric pressure sensor and piezoresistive pressure sensor .Finding out the most precise one of the pressure sensors mode is via system identification of various methods, for example, identification method of ARX、ARMAX and OE. The modeled mode reveals dynamic characteristics performance index including transfer function, resonate frequency and resonate magnitude of the pressure sensors.

博士
國立臺北科技大學
機電科技研究所
94
This thesis applies experimental and analytical methods to investigate the dynamic characteristics of various kinds of pressure sensors and to identify the response of two hydraulic hose systems by using piezoelectric pressure sensors with identical structure and specification, which are connected directly at the inlet and outlet sections of the piping devices with different lengths and diameters. Fully filled with the fluid, the hoses are experimented to investigate the relationship between the damping and frequency response. The experimental results have indicated that the applied sensors have a significant influence on the output of both time-domain and frequency-domain response of the tested hoses. The objectives of this study include the following two folds: (a) the analysis of the differences of the output response between the different types of pressure sensors, (b) the investigation of the fundamental damping phenomena in a hydraulic hose system. Because of the flexible hoses are widely used in hydraulic equipment for the power transfer. Therefore, this study would contribute to the design and application of the hydraulic power system. Square waves are commonly used for system identification. However, it is difficult to generate ideal pressure square waves in hydraulic system. Because the hydraulic fluid possesses compressibility, viscosity, and inertia, these properties would result in the undesired delay between pressure and signal transformation in a hydraulic power system. In this research, an experimental device is called pressure square wave generator (PSWG), which has been developed to generate pressure square-like waves by use of the differential principle. The pressure square-like waves can be employed in dynamic analysis for the full hydraulic system or individual component. In this research, an efficient procedure is developed to measure both the time-domain and frequency-domain response of various pressure sensors. Results indicate that each sensor exhibits extremely different dynamic characteristics. The piezoelectric pressure sensors based on quartz material possess larger overshoots and bandwidth, and shorter rise time in comparison with the ones based on strain type sensor. In addition, to illustrate the damping effect in the hydraulic hose systems, two piezoelectric pressure sensors are used to study the hose dynamic characteristics under various operating frequencies with various hose lengths and diameters. Frequency response analysis has been established by use of a series of experimental data and interpretation. The frequency response includes logarithmic magnitude and phase characteristics . Results conclude the following six findings: (1) the larger the hose length used, the amplitudes of pressure between the hose inlet and its outlet decay with a function of parabola. Furthermore, the larger the hose diameters, the amplitudes decay with a function of exponent. (2) The larger hose length or diameter was used, the smaller the obtained. However, the can not be found as the hose length is 1000 mm or hose diameter is 5/8 inches. (3) The corresponding resonant frequency is lower when the larger hose length or diameter was used. Similarly, the also can not be found when the hose length is 1000 mm or hose diameter is 5/8 inches. (4) the difference of bandwidth (BW) is not significant when the hose length is less than 750 mm. The bandwidth decreases when the hose length is 1000 mm. (5) the hose diameter has a great affect on the bandwidth. Lower bandwidth is obtained when the hose diameter increases. However, the bandwidth also cannot be calculated when the hose diameter is 5/8 inches. (6) The hydraulic hose transfer function includes a complex conjugate pole, a first-order pole, a first-order zero, and a time delay factor.

碩士
國立清華大學
資訊工程學系所
106
Gait analysis has become prevalent in many fields such as sports biomechanics, medical diagnostics, and injury prevention. For the plantar pressure dynamic estimation in gait analysis, the vertical component of ground reaction force (vGRF) and center of pressure (CoP) trajectories are vital parameters about human locomotion and balance. Three main approaches are used in measuring the gait parameters, namely computer vision, floor sensors, and wearables. Though the first two techniques are accurate, they are expensive and limited in the sensing area. The wearable devices have advantages in portable and low cost. However, the contact sensing like pressure detector suffers from long-term reliability. In this research, we employ the 6DOF inertial measurement unit (IMU) (gyro system, Taiwan) to estimate the vGRF and CoP trajectories. Unlike conventional pressure sensing, IMUs are low cost and durable. Four IMUs are attached on the heel of two feet, left shank, and waist. F-scan pressure sensing system serves as the ground truth. Associated with hardware setup, we propose a LSTM model to predict vGRF and CoP, based on the acceleration and angle velocity data from IMUs. The data synchronization, data formation, and LSTM structure are explained. Under 33,880 sample points of normal walks, the first 70% is for training and the last 30% is for testing. Experiment shows the root mean square error of peak value of vGRF is equal to 4.83N, the error is 4.025% and the root mean square error of CoP excursion is 0.14cm.