Dissertations / Theses on the topic 'Displacement curent sensor'

This dissertation presents the design and development of a high precision driver for an eddy current displacement sensor. The project was initiated to supplement the development of a low-cost PCB eddy current displacement sensor for active magnetic bearings (AMBs). The sensor driver will be implemented in AMB systems that will be used in various high-speed applications. The sensor driver is required to drive an eddy current PCB sensor, condition the output signals from the sensor, and send the conditioned position signals to an embedded digital controller. Circuit board design and development therefore constitute the main focus of this project. Research on the defining concepts of the project was imperative in gaining the necessary understanding of the project. AMB systems and the sensors used in these systems were investigated first. The eddycurrent type sensor used in this project, as well as the PCB sensor technology used were also researched. As analogue design constituted a main aspect of this project, the concepts of signal conditioning and sensor characteristics had to be comprehended. The sensor driver consists of several sub-systems, including a sensor excitation circuit to drive the sensor, a signal conditioning circuit to condition the output signals of the sensor, and a digital processing circuit for further processing of the position signals. A conceptual design was performed for each of these sub-systems, followed by a detail design, in which the conceptual designs of the sub-systems were realized. All the sub-systems were then integrated, and lastly evaluated. The evaluation of the sensor driver system included verification and validation of the system. The sensor driver design was verified, while the final sensor driver board was validated with regards to its specifications. Additional circuit characteristics such as signal-to-noise-ratio, sensitivity and resolution were also determined in order to characterize the sensor driver system. The overall outcome of the sensor driver project was successful, with all the characteristics of the sensor adhering to the requirements. It was determined that the sensor driver has a signal to noise ratio of 54 dB, a linearity of 9 %, a sensitivity of 26 .4 V/mm, and a resolution of 792.5 nm. Recommendations are made with regards to the sensor cables, heat distribution, and the low-pass filter on the field programmable gate array (FPGA). Future work will mainly focus on implementation of the sensor driver on a test bench and implementation of the linearization algorithm. Additional future work includes a study on EMC effects on the system and especially the cables, and further firmware enhancements of the sensor driver. These include input signal testing and temperature compensation. An investigation on the required excitation current for optimal sensor operation should also be done.
Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2010

The McTronX research group of the North-West University is involved in active magnetic bearing (AMB) research. An AMB is a mechatronic system that levitates a rotating axis with electromagnetic forces. The group has successfully implemented radial and axial AMBs as well as a complete flywheel energy storage system operating at 22 000 rpm. Research is also done on using the actuator voltage and current to derive rotor position, also known as self-sensing, but these methods have not been perfected. Position measurement is very important in AMBs, since it is the main control variable. The literature indicates that the eddy current phenomenon is well suited for displacement measurement, since it is relatively noise immune and insensitive to process medium when a nonmagnetic and non-conductive substance is used. Printed circuit board (PCB) sensors must be considered when low cost is a requirement. The goal of this project is to design, simulate, manufacture and test a PCB based, low cost eddy current displacement sensor for AMBs. This project will focus on the sensor (probe) that converts the physical rotor movement to an electric signal. An evaluation platform, used to test the PCB sensor, is also designed and manufactured as part of this project. The first step in the sensor design is to establish a suitable software model. A finite element method (FEM) software package, Comsol® , is used to realise a FEM model of the sensor. This FEM model is used to simulate sensor behaviour in various configurations. The trends found in the FEM model results are used to compile a design flow diagram. This diagram is illustrated by applying it to single, double- and five-layer designs. The single- and double-layer sensors are manufactured and tested to validate the accuracy of the FEM model and design flow diagram. Close correlation between the practical and predicted results is found for the single- and double layer sensors. The sensitivity and working point rms voltage correlated exceptionally well for both sensors. Linearity does not correlate as closely due to the evaluation platform and circuitry but is still within acceptable limits when compared to other displacement sensors used in AMBs. This project laid the foundation for PCB sensor design in the McTronX group. A comparison between the different sensors showed that the double-layer sensor is the best choice in terms of cost and performance. It is concluded that the PCB displacement sensor presented in this dissertation is a viable low cost option for displacement measurement in AMBs.
The McTronX research group of the North-West University is involved in active magnetic bearing (AMB) research. An AMB is a mechatronic system that levitates a rotating axis with electromagnetic forces. The group has successfully implemented radial and axial AMBs as well as a complete flywheel energy storage system operating at 22 000 rpm. Research is also done on using the actuator voltage and current to derive rotor position, also known as self-sensing, but these methods have not been perfected. Position measurement is very important in AMBs, since it is the main control variable. The literature indicates that the eddy current phenomenon is well suited for displacement measurement, since it is relatively noise immune and insensitive to process medium when a nonmagnetic and non-conductive substance is used. Printed circuit board (PCB) sensors must be considered when low cost is a requirement. The goal of this project is to design, simulate, manufacture and test a PCB based, low cost eddy current is placement sensor for AMBs. This project will focus on the sensor (probe) that converts the physical rotor movement to an electric signal. An evaluation platform, used to test the PCB sensor, is also designed and manufactured as part of this project. The first step in the sensor design is to establish a suitable software model. A finite element method (FEM) software package, Comsol, is used to realise a FEM model of the sensor. This FEM model is used to simulate sensor behaviour in various configurations. The trends found in the FEM model results are used to compile a design flow diagram. This diagram is illustrated by applying it to single, double- and five-layer designs. The single- and double-layer sensors are manufactured and tested to validate the accuracy of the FEM model and design flow diagram. Close correlation between the practical and predicted results is found for the single- and double layer sensors. The sensitivity and working point rms voltage correlated exceptionally well for both sensors. Linearity does not correlate as closely due to the evaluation platform and circuitry but is still within acceptable limits when compared to other displacement sensors used in AMBs. This project laid the foundation for PCB sensor design in the McTronX group. A comparison between the different sensors showed that the double-layer sensor is the best choice in terms of cost and performance. It is concluded that the PCB displacement sensor presented in this dissertation is a viable low cost option for displacement measurement in AMBs.
Thesis (M.Ing. (Electrical Engineering)--North-West University, Potchefstroom Campus, 2008.

Over the last several decades, electricity consumption and generation have continually grown. Investment in the Transmission and Distribution (T&D) infrastructure has been minimal and it has become increasingly difficult and expensive to permit and build new power lines. At the same time, a growing increase in the penetration of renewable energy resources is causing an unprecedented level of dynamics on the grid. Consequently, the power grid is congested and under stress. To compound the situation, the utilities do not possess detailed information on the status and operating margins on their assets in order to use them optimally. The task of monitoring asset status and optimizing asset utilization for the electric power industry seems particularly challenging, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles. The lack of situational awareness compromises system reliability, and raises the possibility of power outages and even cascading blackouts. To address this problem, a conceptual Power Line Sensor Network (PLSN) is proposed in this research. The main objective of this research is to develop a distributed PLSN to provide continuous on-line monitoring of the geographically dispersed power grid by using hundreds of thousands of low-cost, autonomous, smart, and communication-enabled Power Line Sensor (PLS) modules thus to improve the utilization and reliability of the existing power system. The proposed PLSN specifically targets the use of passive sensing techniques, focusing on monitoring the real-time dynamic capacity of a specific span of a power line under present weather conditions by using computational intelligence technologies. An ancillary function is to detect the presence of incipient failures along overhead power lines via monitoring and characterizing the electromagnetic fields around overhead conductors. This research integrates detailed modeling of the power lines and the physical manifestations of the parameters being sensed, with pattern recognition technologies. Key issues of this research also include design of a prototype PLS module with integrated sensing, power and communication functions, and validation of the Wireless Sensor Network (WSN) technology integrated to this proposed PLSN.

L' imagerie spatiale est aujourd'hui un outil indispensable au développement durable, à la recherche et aux innovations scientifiques ainsi qu’à la sécurité et la défense. Fort de ses excellentes performances électro-optiques, de son fort taux d’intégration et de la faible puissance nécessaire à son fonctionnement, le capteur d’images CMOS apparait comme un candidat sérieux pour ce type d’application. Cependant, cette technologie d’imageur doit être capable de résister à l’environnement radiatif spatial hostile pouvant dégrader les performances des composants électroniques. Un nombre important d’études précédentes sont consacrées à l’impact des effets ionisants sur les imageurs CMOS, montrant leur robustesse et des voies de durcissement face à de telles radiations. Les conclusions de ces travaux soulignent l’importance d’étudier les effets non-ionisants, devenant prépondérant dans les imageurs utilisant les dernières évolutions de la technologie CMOS. Par conséquent, l’objectif de ces travaux de thèse est d’étudier l’impact des effets non-ionisants sur les imageurs CMOS. Ces effets, regroupés sous le nom de déplacements atomiques, sont étudiés sur un nombre important de capteurs d’images CMOS et de structures de test. Ces dispositifs sont conçus avec des procédés de fabrication CMOS différents et en utilisant des variations de règle de dessin afin d’investiguer des tendances de dégradation commune à la technologie d’imager CMOS. Dans ces travaux, une équivalence entre les irradiations aux protons et aux neutrons est mise en évidence grâce à des caractéristiques courant-tension et des mesures de spectroscopie transitoire de niveau profond. Ces résultats soulignent la pertinence des irradiations aux neutrons pour étudier les effets non-ionisants. L’augmentation et la déformation de l’histogramme de courant d’obscurité ainsi que le signal télégraphique aléatoire associé, qui devient le facteur limitant des futures applications d’imagerie spatiale, sont évalué et modélisés. Des paramètres génériques d’évaluation des effets des déplacements atomiques sont mis en évidence, permettant de prévoir le comportement des capteurs d’images CMOS en environnement radiatif spatial. Enfin, des méthodes d’atténuation et des voies de durcissement des imageurs CMOS limitant l’impact des déplacements atomiques sont proposées
Today, space imaging is an essential tool for sustainable development, research and scientific innovation as well as security and defense. Thanks to their good electro-optic performances and low power consumption, CMOS image sensors are serious candidates to equip future space instruments. However, it is important to know and understand the behavior of this imager technology when it faces the space radiation environment which could damage devices performances. Many previous studies have been focused on ionizing effects in CMOS imagers, showing their hardness and several hardening-by-design techniques against such radiations. The conclusions of these works emphasized the need to study non-ionizing effects which have become a major issue in the last generation of CMOS image sensors. Therefore, this research work focuses on non-ionizing effects in CMOS image sensors. These effects, also called displacement damage, are investigated on a large number of CMOS imagers and test structures. These devices are designed using several CMOS processes and using design rule changes in order to observe possible common behaviors in CMOS technology. Similarities have been shown between proton and neutron irradiations using current-voltage characteristics and deep level transient spectroscopy. These results emphasize the relevance of neutron irradiations for an accurate study of the non-ionizing effects. Then, displacement damage induced dark current increase as well as the associated random telegraph signal are measured and modeled. Common evaluation parameters to investigate displacement damage are found, allowing imager behavior prediction in space radiation environment. Finally, specific methods and hardening-by-design techniques to mitigate displacement damage are proposed

Les capteurs d'images sont utilisés dans diverses applications spatiales : observation spatiale, calcul d'attitude etc. Ces capteurs évoluent dans l’environnement spatial dont les rayonnements entraînent une dégradation de leurs performances. Parmi les paramètres impactés, nous nous intéressons au courant d'obscurité des pixels. Ce courant parasite correspond à la génération de porteurs de charges sans lumière par simple excitation thermique, induisant l'augmentation du bruit de fond des images. Les pixels fortement dégradés sont particulièrement pénalisants pour les missions spatiales. Cet effet pousse donc la communauté spatiale à développer des méthodes de prédiction performantes. L'ONERA a développé une méthode originale de prédiction des courants d'obscurité basée sur la méthode de Monte Carlo et la librairie GEANT4. L’objectif de la thèse est d’améliorer la prédiction de l’outil. Dans un premier temps, nous avons modifié l'outil numérique pour des cas extrêmes de modélisations pour lesquels les modélisations Monte Carlo sont trop longues. Pour cela, nous avons développé des méthodes utilisant des simplifications statistiques. Dans un second temps, nous avons étudié l’influence de la géométrie du pixel sur le courant d'obscurité. L’idée est de suivre les cascades de dégradations générées par les particules spatiales et de déterminer si ces cascades restent confinées au sein du pixel impacté ou si elles se propagent dans les pixels voisins. Enfin, nous avons élaboré dans notre outil un modèle simulant les mécanismes liés au champ électrique potentiellement responsables des dégradations les plus élevées, les effets Poole-Frenkel et tunnel assisté par phonons
Image sensors are used in various space applications: space and earth observations, attitude calculation etc. Those sensors are very sensitive to the space environment whose radiations lead to a degradation of their performances. Among the different impacted parameters, we are interested in the increase of dark current in the pixels. This parasitic current is caused by the thermal generation of charge carriers without any light excitation inducing the increase of the background noise on the images. Some pixels exhibiting the highest degradation are particularly disadvantageous for space missions. They can be critical for some missions and impose to the space community to develop effective prediction methods. ONERA developed an original method to predict dark current induce by the space radiations, based on a Monte Carlo method and the GEANT4 library. The objective of the PhD is to improve the performances of the tool. The approach of this work is first to modify the numerical tool for extreme cases of modelling (i.e. high fluencies or huge pixel volume) for which the Monte Carlo simulations are too long. In order to reduce this computation time, we developed calculation methods using statistical simplifications. In a second part, we studied the influence of the pixel geometry on the dark current. The idea is to follow the degradation cascades created by space particles and to determine if those cascades are contained in the impacted pixel or if they reach neighbor pixels. Finally, we modelled in our tool the physical mechanisms potentially responsible of the highest degradations linked to the electric field, the Poole-Frenkel effect and the phonon assisted tunneling

Inspirés des technologies microélectroniques CMOS (Complementary Metal Oxide Semiconductor), les capteurs d’images CMOS sont largement utilisés dans de nombreuses applications grand public et prédominent sur le marché commercial des caméras intégrées. Au cours de la dernière décennie, de nombreuses avancées technologiques ont permis au capteur d’image CMOS d’atteindre d’excellentes performances ainsi qu’une faible consommation d’énergie. Par conséquent, ces imageurs deviennent des candidats essentiels pour un nombre croissant d’applications spatiales et nucléaires. Cependant, le comportement de ces dispositifs microélectroniques dans les environnements radiatifs nucléaires et spatiaux est encore mal compris. Par conséquent, il est nécessaire d’étudier les différents mécanismes qui conduisent à la dégradation des performances des capteurs d’images CMOS et en particulier à l’augmentation du courant d’obscurité, un signal parasite qui augmente avec les doses de radiations.Parmi ces doses de radiations, la dose dite de déplacement, relative à l’altération de la structure cristalline du silicium, reste peu étudiée par rapport à la dose dite ionisante. Dans les dernières technologies de capteurs d’images CMOS utilisant des photodiodes pincées, la dose ionisante n’est plus le mécanisme de dégradation dominant dès lors que la dose de déplacement est mise en jeu. La dose de déplacement devient le mécanisme de dégradation principal qui conduit à l’augmentation du courant d’obscurité. Ce travail se concentre principalement sur le rôle des défauts cristallins, créés par la dose de déplacement induits par les radiations, dans l’augmentation du courant d’obscurité des capteurs d’images CMOS. Un intérêt particulier est accordé aux défauts métastables qui sont probablement la cause des fluctuations discrètes et aléatoires du courant d’obscurité appelé : signal des télégraphistes. Cette étude présente un double enjeu :Le premier vise à contribuer à l’amélioration des connaissances des principes physiques mis en jeu dans le silicium cristallin face aux radiations. Les interactions particule-matière,associées à l’architecture spécifique des capteurs d’images, visent à fournir des outils fiables pour l’analyse des défauts induits par les radiations dans le silicium. Ces observations et résultats peuvent être étendus à tous les dispositifs à base de silicium et plus généralement aux autres dispositifs à semi conducteurs.Le second vise à identifier les différents mécanismes conduisant à l’augmentation du courant d’obscurité des capteurs d’images CMOS lorsqu’ils fonctionnent dans des environnements radiatifs. L’étude vise à identifier et à améliorer la connaissance des comportements des sources de courant d’obscurité dans le but d’optimiser les capteurs d’images CMOS pour les futures applications spatiales et nucléaires
Inspired by the microelectronic Complementary Metal Oxide Semiconductor (CMOS) technologies, CMOS image sensors are widely used in many consumer-grade applications and are predominant in the commercial market for embedded cameras. Over the past decade,numerous technological advances allowed state-of-the-art CMOS image sensors to achieve excellent performances as well as low-power consumption. Therefore, CMOS image sensors are becoming essential candidates for a growing number of high-end applications such as space and nuclear applications. However, the behavior of these microelectronic devices inspace and nuclear radiative environments is still under understanding. Hence, studies still investigate the different mechanisms that lead to the degradation of CMOS image sensor performances including the radiation-induced dark current increase, a parasitic signal that increases with radiation doses. Among these radiation doses, the so-called displacement dose,relative to the alteration of the crystalline structure of the silicon, remains poorly studied compared to the so-called ionizing dose. In the latest CMOS image sensor technologies using pinned photodiodes, the ionizing dose is no longer the main degradation mechanism when the displacement dose is at stake. From then on, the displacement dose becomes the principal degradation mechanism that leads to the dark current increase. This work mainly focuses onthe role of the crystalline defects, created by radiation-induced displacement damage, in the CMOS image sensor dark current increase. Particular interest is given to metastable defects,which are probably the cause of discrete and random fluctuations of the dark current called : Dark Current Random Telegraph Signal (DC-RTS). This study presents a double objective :The first aims to contribute to improving knowledge of the physical principles involved in crystalline silicon when facing radiations. Particle-matter interactions, combined with the specific architecture of image sensors, aim to provide reliable tools to analyze the radiation induced defects in silicon. Observations and findings can be extended to all silicon-based devices and more generally to other semiconductor-based devices.The second seeks to identify the different mechanisms leading to CMOS image sensor dark current increase when operating in radiative environments. The study aims to identify and improve knowledge on the behavior of dark current sources aiming to optimize CMOS image sensors for future space and nuclear applications

Ce travail de thèse porte sur le développement d'outils de modélisation pour le contrôle non destructif (CND) par courants de Foucault (CF). Il existe actuellement une tendance à la mise en œuvre de capteurs souples qui représentent une solution pertinente pour inspecter des pièces ayant une surface complexe. L'objectif principal de cette thèse est l'élaboration de techniques permettant la modélisation de ce type de capteurs au sein de la méthode des éléments finis (MEF).Lors de la modélisation d'un capteur souple avec la MEF, trois problématiques se manifestent. La première concerne le maillage des milieux fins qui apparaissent dans ce type de configuration (distance capteur-pièce contrôlée, bobine plate, revêtement fin...). Le maillage de ces régions par des éléments simpliciaux peut poser des problèmes numériques (éléments déformés quand un maillage grossier est considéré et grand nombre d'inconnues quand un maillage fin est utilisé). La deuxième problématique concerne le déplacement du capteur. Si les différents sous-domaines géométriques (air, pièce, capteur...) sont convenablement remaillés pour chaque position du capteur, le temps total pourra être pénalisant. La troisième problématique relative à la modélisation d'un capteur souple porte sur l'imposition du courant dans des bobines déformées.Une comparaison de différentes approches nous a conduit à retenir la méthode overlapping, qui permet de considérer simultanément des milieux fins avec maillages non-conformes. Cette méthode permet d'effectuer le recollement de deux surfaces non planes et/ou de géométries différentes. La méthode overlapping a été implantée dans deux formulations duales (magnétique et électrique) en 2D et 3D intégrées dans le code de calcul DOLMEN (C++) du LGEP. La méthode overlapping a été validée pour la prise en compte de plusieurs types de régions minces (air, milieux conducteurs, milieux magnétiques, bobines plates...). La modélisation des capteurs souples nécessite aussi l'implantation d'une technique permettant d'imposer correctement les courants dans un inducteur de forme arbitraire. Une technique a été sélectionnée et programmée, d'abord pour des bobines classiques (volumiques) déformées puis pour des bobines plates flexibles. Afin de valider les développements réalisés, différentes configurations de test ont été traitées et les résultats comparés avec des solutions de référence analytiques ou expérimentales.

Eddy current (EC) based testing and measurement methods are well known in non-destructive testing (NDT) world. EC sensors are extensively studied and used for material health monitoring and its property measurement. Target displacement measurement is one of the well-known applications of EC method. The main advantage of EC sensor is its working capability in harsh environment like humidity, contamination etc. It is non-contact, rugged and requires less maintenance. The range and sensitivity of target displacement is mainly determined by the probe geometry and its construction method. Also displacement measurement depends upon geometry and electromagnetic (EM) properties of the target plate. Any variation of ambient temperature alters the EM properties of the probe as well as EM properties of the target. Thus, many parameters like geometry, EM properties and temperature involved in target displacement measurement. Hence, while using EC sensor for displacement measurement, it demands careful design and measurement procedure to achieve high sensitivity and high precision with low temperature drift. To achieve these, we present the following. 1) A temperature compensation technique 2) Optimization of probe geometry and its construction method to increase the range and sensitivity 3) Selection of suitable probe measurement parameter (Z, R, X) based on target material properties 4) Making the displacement measurement less sensitive to tolerance in probe construction parameter. A temperature compensation technique for target displacement measurement, using a self-running LC oscillator has been presented. A sensing coil is energized by a Hartley oscillator. The oscillator voltage is maintained at a constant level by a closed loop feedback circuit and the average feedback current to the oscillator is measured for target displacement detection. The temperature drift of the feedback current is compensated by applying temperature compensation function (TCF) and this is verified experimentally. Cold rolled mild steel (carbon steel) is taken as a target material and the sensor is tested over a temperature range of 20 °C – 80 °C. It shows that the temperature drift is less than ±30 ppm/°C over 3 mm target displacement. To match all the sensor modules in mass production, components selection procedure is presented. To avoid mismatch across sensors in manufacturing process, the transistor based oscillator is modified with operational trans-conductance amplifier (OTA). The same temperature compensation formula (TCF) is applied to compensate the temperature drift of feedback current and achieved intended accuracy. Geometry and construction parameters of the eddy current sensing probe is optimized for target displacement measurement using Ansoft Maxwell, electromagnetic design software. EC probe with different geometry are analyzed in search of suitable geometry for target displacement measurement. Four shapes of commercially available core have been chosen for probe construction. For each shape of sensing probe, the radius and height of the probe is increased by 0 mm to 9 mm to find the effect of them on sensitivity and range of target displacement measurement. It has been observed that the probe with less height and maximum diameter has shown better performance. In addition to that, the probe geometry is optimized to achieve more sensitivity and range within the space available for probe mounting. It helps to utilize the available space effectively for probe design. Coil winding and mount-ing it inside the core window also important parameter in probe design. It has been observed that de-pressing the sensing coil inside the core window from sensing face by 3 mm decreases the sensitivity by 40 %. Hence, it is recommended to place the coil on the extreme end of the sensing face of the core. To know the effect of core permeability, it is varied from 1000 to 15000. It has been observed that it has no effect on sensitivity and measurement range. Only optimizing the probe geometry and its construction method is not adequate for target displacement measurement. We know that the EC based displacement measurement is also target material dependent. Generally probe impedance is measured and then the temperature drift of the sensing coil resistance is compensated to know the target displacement. Most of the temperature compensation techniques use this compensation technique and it is shown that those are suitable for high conductivity targets like copper. Choosing Z for displacement measurement may not be only best choice for all target materials. The displacement can be measured also through either R or X of the probe. Choosing the proper probe parameter for a given target material will provide a less temperature drift for target displacement measurement. To know about this, a simulation has been made for target displacement measurement with target metal of μr = 1, relative permittivity εr =1, and temperature coefficient of resistivity ∝ = 0.004 K-1. The conductivity (σ) of the target is varied from 1×106 S/m to 62×106 S/m in the temperature range of 20 ℃ – 80 ℃. Now the simulation has been repeated by fixing  as a constant and varying target μr. The metal plate with  = 1×106 S/m, εr=1 and ∝ = 0.004 K – 1 is taken as a target and μr is varied from 100 to 10000. For both conductivity and permeability sweep analysis, the target displacement is measured as a function of Z, R and X independently. The temperature drift in displacement measurement is also analysed for the above temperature range. An experiment has been conducted with copper, stainless steel and mild steel as target metal in the temperature range of 20 ℃ – 80 ℃. The temperature drift is calculated when the displacement is measured as function of Z, R and X. Based on the results, we have identified that the target material relative permeability determines the selection of probe measurement parameter for target displacement measurement. Hence, knowing tar-get r alone suffice to select the probe measurement parameter (Z or R or X) for displacement measurement. Optimizing the probe geometry, selecting the proper probe measurement parameter and temperature compensation technique suffice to provide a good sensitivity, range and low temperature drift for a single probe. But in general, one of the mass produced probes is selected as a reference probe and it is calibrated against the ambient temperature and target displacement. And the calibration curves are loaded to all the probes. Matching the probe construction parameters to each other across the production patches is not possible in mass production. This makes the temperature compensation function and displacement calibration are different for every individual probes for displacement measurement. This degrades the measurement accuracy. A simulation has been performed with pot core with commercial tolerance. Using this, we have obtained 24 probes due to variations in 1) Individual and few combinational variations in core and coil dimensions 2) Core permeability variation and 3) relative position of the coil with respect to core. Finally, we have quantified the displacement error for each probe. We have identified the important probe dimensional parameters that have to be controlled precisely in mass production to improve the measurement accuracy. It shows error of 0.86 % in the displacement measurement when the relative reactance and relative displacement is used for measurement. In practice, error in displacement measurement due to both the ambient temperature drift and the tolerance in probe construction parameter exist simultaneously. Hence, the combined error is computed for the target displacement range of 0 mm – 3 mm for the temperature range of 0 °C – 100 °C. The total error of less than 1 % is achieved for commercial standard probe tolerance. Finally, we have provided general factory production procedure and user calibration procedure of probe design to achieve cost effective displacement measurement with sensitivity and range with low temperature drift.

碩士
國立臺灣大學
機械工程學研究所
90
The aim of this thesis is to develop a reliable and precise eddy-current displacement sensor which can meet the need of general displacement sensing, and use it to establish the multi-degrees displacement sensing system. First of all, the design guidelines of an eddy-current displacement sensor were built up through literature survey and theoretical analysis. The eddy-current sensor consists of two parts — a sensing coil and a sensing circuit. According to the analytical and empirical testing results, the sensing coil is decided to use the wrapping flat coil. On the other hand, an amplitude-modulated circuit and a differential bridge circuit are made as sensing circuits according to different sensing concepts. These two different types of eddy-current displacement sensors are then proceeded different static and dynamic performance testings. Besides, a novel concept of planar coil matrix arrangement based on the modulated sensor is constructed and is tested for proving its adaptability to the multi-degrees displacement sensing system.

碩士
國立高雄第一科技大學
系統資訊與控制研究所
98
In this thesis, an eddy current displacement sensor consisted of stacked coil with a block width of 1 mm is developed by MEMS (Micro-Electro-Mechanical System) technology. The features of coil are small volume, heat resistance and moisture resistance. The performances of developed sensor are verified through experimental results. The sensor coils are formed by four basic patterns, which are made of LTCC (Low Temperature Co–fired Ceramics). The shape of basic pattern is like a three quarters circle, and four basic patterns are combined together to form a spiral structure. A coaxial cable is used to connect the basic patterns, and the sensor head consisting of spiral coils is installed into an experimental fixture. The sensor head is excited by a 5 MHz oscillation signal generated by a quartz resonator. A special circuit is implemented to detect the variation of coil impedance, and then converted into voltage signal. The accuracy of the eddy current displacement sensor is ± 0.1 μm in a measuring range of 100 μm. In addition, for further sensor design, a study is performed for demonstrating the effects of coil patterns to the quality factor by simulation method. This eddy current displacement sensor developed in this thesis can be used for detecting the thickness of lubricant in rotating machinery operated in liquid environment.

碩士
國立高雄應用科技大學
機械與精密工程研究所
98
In this study , the design of the highly linear eddy-current displacement detector is investigated. The sensor head is a LC resonating circuit consists of a ferrite-cored wire-wound inductor and a ceramic capacitor. The driving circuit is an ac impedance measurement circuit constructed from several elements, including crystal oscillator, analog mixer, etc. According to the fitting results of theoretical and experimental resonance curves, the distance of conducting target affects both the inductance and the parasitic resistance of the sensor. For the reducing target distance, the change in inductance alters the resonance frequency, which results in the change in impedance of LC circuit under the fixed excitation frequency. The linearity of the sensor can be optimized by tuning the capacitance in parallel. The developed sensor is capable of dynamic measurement of the distance for conducting and magnetic targets, which is important for automation and motion control applications.

碩士
國立臺北科技大學
機械工程系機電整合碩士班
107
This research aims to develop and design a simple low-power, low-cost eddy current and capacitance displacement sensor circuit. The main features are small size, high precision, low cost, and the combination of processing circuit and probe. It is divided into three parts. The first part is to explore the design and verification of the circuit, to detect the system power consumption or leakage current through the circuit of the smart parking system (PKS), and to plan a complete inspection process architecture, which will be provided to the laboratory designers. Second part, a capacitance sensor. Using the principle of parallel plate capacitance to design a low-cost, small-sized sensor, and accurately calculate the electrode area of the probe and guardring size through the capacitance formula. The third part is the eddy current displacement sensor, which uses the principle of eddy current and electromagnetic induction, is composed of an excitation coil and a conductive object, and the measuring coil is fabricated by using a PCB(Print circuit board) technology. The concept of small size and low cost is realized. Both of the objectives are applied to the CNC(Computer numerical control) to measure the displacement error of the cutting and various components to realize the application of the future intelligent tool machine.

碩士
正修科技大學
電機工程研究所
100
For normal operation of the rotating machinery system, detecting and preventing the incipient faults of the machinery is an important task, especially in the production lines of the high-technology industry. If the incipient fault cannot be detected in its early stage, then it will lead to the serious faults. The close coupling of the machinery leads to the cause of its vibration faults more diverse and complicated; however, the vibration status is still a vital indicator for identifying whether the machinery operates normally or not. Therefore, rotating machines’ vibration monitoring and fault diagnosis method is not only significant in productivity and economic benefits of high-technology industry, but also an important research topic in the field of electrical engineering. Vibration faults of rotating machinery are with diverse characteristics. Although the traditional error back-propagation neural network can be used to diagnose the vibration faults, it is with a long training time and its parameters are difficult to be determined. Therefore, to solve the vibration signal measurement and fault diagnosis of rotating ma-chinery, this study first used the eddy current displacement to measure vibration signals, then the Particle Swarm Optimization (PSO) tuned Radial Basis Function Neural Net-work (RBFNN) model diagnosed the vibration faults. This study has proposed PSO to adjust the parameter of the RBFNN, and model performances of the optimal diagnosis model obtained were compared with those of the traditional neural networks. Test results have shown that the proposed methods are with less model constructing time and higher diagnosis accuracy than those of the traditional methods. Therefore, this study has con-firmed the feasibility of the proposed approach to practical system applications. Keywords: Radial Basis Function Neural Network (RBFNN), Particle Swarm Optimiza-tion (PSO) Algorithm, Fault diagnosis.