Currently in the marketplace, one of the important goals is to improve quality, and reliability. There is great interest in the engineering community to develop a field calibration technique concerning piezoelectric pressure sensor to reduce cost and improve reliability. This paper summarizes the algorithm used to characterize and develop a model for a piezoelectric pressure transducer. The basic concept of the method is to excite the sensor using an electric force to capture the signature characteristic of the pressure transducer. This document presents the frequency curve fitted model based on the high frequency excitation of the piezoelectric pressure transducer. It also presents the time domain model of the sensor. The time domain response of the frequency curve fitted model obtained in parallel with the frequency response of the time domain model and the comparison results are discussed. Moreover, the relation between model parameters and sensitivity extensively is investigated. In order to detect damage and monitor the condition of the sensor on line the resonance frequency comparison method is presented. The relationship between sensitivity and the resonance frequency characteristic of the sensor extensively is investigated. The method of resonance monitoring greatly reduces the cost of hardware. This work concludes with a software implementation of the signature comparison of the sensor based on a study of the experimental data. The software would be implemented in the control system. / Master of Science

This thesis describes the design of a DSP based air detector system to prevent air embolism during Hemodialysis, which is a treatment option for kidney failure disease. Hemodialysis consists of removing blood from the body, filtering and treating the blood to remove toxic substances such as wastes and fluids, reestablishing proper chemical levels in the blood and returning the processed blood to the body. The functions of hemodialysis are performed through the use of a dialyzer, which is also known as an artificial kidney. During hemodialysis small air bubbles may infiltrate the tubing used during the therapy and combine to form larger air bubbles that are harmful to the patient. If an air bubble is large enough and enters the patient's circulatory system, the blood flow can be blocked and the patient can die by embolism. Most of the hemodialysis instruments in use today are equipped with air detection systems, which are based on analog design and digital microcontroll ers. This thesis presents a design method based strictly on DSP technology. The Motorola DSP 56824EVM was considered suitable for this biomedical application since its performance parameters include high-speed, multi-signal control capability, reliability and stability. These performance parameters are considered to be the most important when designing biomedical instruments dealing with human beings' life and safety. The objective of this research was the development and implementation of a DSP algorithm for the detection and measurement of the sizes of air bubbles in a fluid. In addition the algorithm had to possess the capability, when appropriate, to initiate protective and awareness measures such as triggering a tube clamp as well as activating visual and audio alarms. The air detection was accomplished by means of a commercial air detector module, which was based on piezo ceramic and ultrasound sensing. The function of the tubing clamp was to stop the fluid flow in the tubing and prevent an air bubble from entering the patient's circulatory system. A secondary goal of this research was to exploit the capability of the DSP 56824EVM and demonstrate its suitability for biomedical applications.

In this study, we discuss AlGaN/GaN high electron-mobility heterostructs grown by metal organic chemical vapor deposition technique. We analyzed the samples by optical and magnetoelectrical experiments to probe the dependence of the piezoelectric effect on the structural difference. We hope our results may be useful for the design of nitride heterostructures. The E-beam evaporator operation manual given in this thesis may be useful for future users.

Veeco Applied EPI 930 molecular beam epitaxy system equipped with a radio frequency plasma assisted nitrogen source has been introduced and the growth procedure and some specialized measurements are also described. The GaN thin films grown by RF-MBE have been talked about nitridation, low temperature GaN buffer layer, and GaN epilayer. The nitridation is a necessary for grown GaN on c-sapphire. From the result of the HRXRD symmetric (002) rocking curve, the magnitude of the FWHM of the GaN films without nitridation was larger than the films with nitridation. The growth temperature of the LT GaN buffer layer was the major factor on the quality of GaN epilayer which grown on the almost without nitridated sapphire substrate. The growth condition of high growth temperature, thin, low growth rate, and low N/Ga ratio of the LT GaN buffer layer can improve the sequent GaN epilayer quality. On the other hand, in the N/Ga flux ratio of GaN epitaxy layer experiment, we have found three interesting results. First, the narrowest peak width of PL spectrum appeared in a slight Ga-rich condition. Second, the smallest of HRXRD FWHM appeared in the nearly stoichiometry condition. Third, the highest electron mobility and less overall dislocations appeared in a slight N-rich condition. Finally, we report the results about AlGaN/GaN heterostructure grown by metalorganic chemical vapor deposition. The piezoelectric effect on the Alx-£_In£_Ga1-xN/GaN heterostructures was investigated and we found that a little In atom in the spacer (£_< 0.01 %) will substantially reduce the strain at interface due to the much larger size of the In atom in comparison to Al and Ga atoms. The electric field at the interface is reduced one order of magnitude smaller than that of the heterostructure without In atom. Two SdH oscillations beat each other due to the population of the lowest two subbands was been seen. Another two SdH oscillations beating have been observed in modulation-doped AlxGa1-xN/GaN heterostructures caused by the finite zero-filed spin splitting due to the inversion-asymmetry-induced bulk k3 term.

No description available.

The theoretical part of this thesis deals with principles and characteristics of the surface acoustic wave filter. It explained the principle of magnetostriction and piezoelectric effect, which uses a filter. In the practical part in the program Comsol Multiphysics are made three simple models of SAW filter. Some modes are founded and are compared to previously known results. In the next phase of project is further studied using the parametric analysis. In the last phase of project is applied global optimization PSO at admittance characteristic from simple 2D structure. The results are compared with the commercially produced devices.

The master’s thesis deals with the proposal of microactuator based on SMART material. The thesis opens with the comparison of SMART materials which are suitable for actuator construction from the point of view of a reaction on stimulation in form of deformation. Subsequent part of the thesis is the report theory of piezoelectric effect, it also describes direct and indirect effects and it concerns about the description of piezoelectric materials. The thesis focuses on several principles of piezoactuators and motors. The last part of the thesis includes modeling and simulation of piezoelectric material in program ANSYS 13.0 and dimensioning geometric of actuator with evaluation of impact of parameters on final motion.

Piezoelectricity crystal is used in different area in industry, such as downhole oil, gas industry, and ballistics. The piezoelectricity crystals are able to create electric fields due to mechanical deformation called the direct piezoelectric effect, or create mechanical deformation due to the effect of electric field called the indirect piezoelectric effect. In this thesis, piezoelectricity effect is the core part. There are 4 parts in the frequency output pressure transducer: two crystal oscillators, phase-locked loop (PLL), mixer, frequency counter. Crystal oscillator is used to activate the piezoelectricity crystal which is made from quartz. The resonance frequency of the piezoelectricity crystal will be increased with the higher pressure applied. The signal of the resonance frequency will be transmitted to the PLL. The function of the PLL is detect the frequency change in the input signal and makes the output of the PLL has the same frequency and same phase with the input signal. The output of the PLL will be transmitted to a Mixer. The mixer has two inputs and one output. One input signal is from the pressure crystal oscillator and another one is from the reference crystal oscillator. The frequency difference of the two signal will transmitted to the frequency counter from the output of the mixer. Thus, the frequency output pressure transducer with a frequency counter is a portable device which is able to measure the pressure without oscilloscope or computer.

L’objectif du présent travail a été de concevoir et de fabriquer des dispositifs sur silicium pour convertir de l’énergie thermique en une énergie électrique en utilisant le changement de phase liquide-gaz dans le but de générer une variation subite de pression suivie d’une conversion d’énergie mécanique vers une énergie électrique à l’aide d’un piézoélectrique. La construction des dispositifs a dû rester simple, avec des matériaux courants et en respectant des limites dimensionnelles. Empreinte inférieure à un diamètre de 20 mm et une épaisseur en dessous des 2 mm.Les prototypes fabriqués sont composés de 3 plaques en silicium, contenant une chambre d’évaporation, une chambre de condensation et un canal réunissant les deux. Un transducteur piézoélectrique a été reporté sur la chambre de condensation et assure l’étanchéité ainsi que la génération d’énergie électrique.Le processus de conception inclut plusieurs étapes, dont la définition de la géométrie et du type de fluide de travail utilisé en tant qu’agent thermique. Le travail effectué a permis de sélectionner le type de piézoélectrique, sa taille ainsi que sa méthode d’intégration. Une étude a également été conduite pour déterminer la méthode optimale d’assemblage des plaques en silicium.La réalisation pratique des dispositifs a été orientée vers la sélection des meilleurs procédés technologiques pour la fabrication des structures. Toutes les expériences ont été conduites en salle blanche avec utilisation de l’oxydation humide, la photolithographie, la gravure KOH, ainsi que d’une technique d’assemblage des plaques silicium avec utilisation de la résine SU-8 comme couche intermédiaire. En plus, quelques outils spécifiques ont été conçus lors du présent travail, pour faciliter la fabrication des dispositifs, dont un système sous vide dédié à l’assemblage des plaques en silicium.Les dispositifs ont été testés afin d’établir leur mécanisme d’oscillation thermique ainsi que leurs propriétés électriques. L’influence tu taux de remplissage et de la température de surface chaude sur le signal en sortie ont également été étudiées. Le calcul de l’énergie générée a aussi été effectué. Dans la dernière partie de l’étude, des étapes d’optimisation pour les dispositifs développés dans le présent travail sont proposées. / The goal of the present work was to design and fabricate a fully silicon oscillating device that converts thermal energy into electricity, applying phenomena of liquid to gas phase-change and piezoelectricity. It should be characterized by simplicity of construction, small size, and ease of manufacture. The diameter should not exceed 2 cm, while the thickness should be within 2 mm.The device was composed of three Si wafers comprising evaporation and condensing chambers, and the channel connecting these two elements. A PZT-based transducer mounted on top of the structure was applied to ensure energy conversion.The design process included the establishment of the device geometry, the type of the working fluid enclosed inside the system, a type, size and assembly technique of a piezoelectric element, as well as a bonding method of several silicon elements of the device.The practical realization of the designed prototypes was aimed at selecting the most suitable technological processes for structure fabrication. All the experiments had been performed in a clean room environment and employed wet oxidation, photolithography, a well-known, easily available wet chemical etching in KOH solution, and a silicon bonding technique with the use of SU-8 photoresist as an intermediate layer. Additionally, during the practical work a few tools have been designed and developed to enhance the device fabrication, amongst which a vacuum pump dedicated to bond the three silicon wafers as structural elements of the prototypesThe fabricated prototypes were tested in terms of oscillation mechanism and electrical properties. The influence of the filling ratio and the hot temperature value on the generated signal was established. Additionally, the power range of the prototypes has been evaluated. In the last part of the study, optimization steps for the devices developed in the present work have been proposed.

科学研究費補助金 研究種目:一般研究(C) 課題番号:01560182 研究代表者:祖父江 信夫 研究期間:1989-1990年度