Free vibration of composite piezoelectric transducers is analyzed by a modified two-dimensional axisymmetric finite element in this study. The modified finite element is formulated based on assumed displacement fields and electric potential, and is capable for three-dimensional analyses of vibration of axisymmetric composite piezoelectric structures. Different arrangements and radius of piezoelectric disk and metal ring, with various thicknesses will be considered and first radial vibration frequencies are derived and their mode shapes are demonstrated, which might be helpful for the design of radial composite transducers. Also, the results of the present study will be compared with those by other methods.

Orientador: Nobuo Oki / Banca: Aparecido Augusto de Carvalho / Banca: Tony Inácio da Silva / Resumo: Este trabalho descreve um sistema de extração de potência de power harvesting utilizando transdutores piezelétricos. Com o objetivo de extrair a máxima potência e assim ter um maior rendimento do sistema, foram projetados e testados alguns circuitos eletrônicos. Um circuito de controle com componentes discretos e de baixo consumo foi projetado para controle da chave do retificador chaveado e bias-flip. A energia extraída será utilizada para alimentar um sistema de aquisição de dados e um sensor de temperatura associado a este sistema. O sistema de power harvesting é constituído por uma estrutura mecânica, transdutor piezelétrico, circuito retificador e um conversor CC-CC. Na estrutura mecânica está localizado o transdutor piezelétrico e este transdutor proporciona a conversão de energia mecânica em energia elétrica. Para efeito deste estudo considera-se que o transdutor piezelétrico comporta-se como uma fonte de tensão alternada, que será retificada e armazenada em um supercapacitor, para depois ser utilizada na alimentação do sistema de aquisição de dados. Os conversores CC-CC são utilizados para maximizar a quantidade de energia obtida do transdutor piezelétrico e fornecer tensão ao supercapacitor. No entanto, uma das limitações desses sistemas é a baixa quantidade de energia gerada por esses dispositivos. Assim, para que haja uma minimização das perdas dos circuitos eletrônicos e possa se extrair a máxima potência possível do piezelétrico obtendo um melhor rendimento do sistema, este trabalho investigará a utilização dos circuitos retificadores em ponte, retificador em ponte chaveado, retificador bias-flip e o conversor buck-boost, além de utilizar a energia armazenada para alimentar um sistema de aquisição de dados associados a um sensor de temperatura... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work describes several circuits for power extracting of power harvesting systems using piezoelectric transducers. In order to extract the maximum power and to achieve the maximum performance of these systems some electronic circuits were projected and tested. A control circuit with discrete components and low power consumption is designed to control switch of the switch-only and bias-flip rectifier. The goal is that the energy extracted is used to supply power electronic devices. That will be, in this work, a temperature sensor that is placed in a difficult access area. The power harvesting system is composed by a mechanical structure, a piezoelectric transducers, a rectifier and a DC-DC converter. The piezoelectric transducers were placed in the mechanical structure, these transducers are responsible to convert mechanical energy into electrical energy. In this work the piezoelectric transducer was considered an AC voltage source. This voltage will be rectified and then stored in supercapacitor, to be used in electronic circuits. The DC-DC converters were used to achieve maximum power from piezoelectric transducer and to supply voltage to the supercapacitor. However, one of the limitations of these systems is the low amount of power generated by the transducer. This way, it is mandatory to reduce the losses at the electronic components and extract the maximum power possible from the piezoelectric to improve the performance. This work investigates the full-bridge rectifier, switch-only rectifier, bias-flip rectifier and buck- boost converter, besides it aims to use the stored energy to supply a temperature sensor. Using the flip-bias rectifier improves the power up to 200%, and the switch-only rectifier by 150% in relation to full-bridge rectifier. And the efficiency changed from 35% (full-bridge)... (Complete abstract click electronic access below) / Mestre

This study presents a high-performance ZnO piezoelectric transducer integrated with the flexible stainless steel substrate. The ZnO piezoelectric film of 1.08nm was deposited on the flexible stainless steel substrate using a RF magnetron sputtering system. The cantilever length of 1cm and the vibration area of 1cm2 were designed for low-frequency environment according to the Cantilever Vibration Theory. The effects of various sputtering parameters such as substrate temperature, RF power and sputtering pressure were investigated to improve the piezoelectric characteristics of ZnO thin films. It was also discussed the unit thickness of open voltage values, and then the optimal sputtering parameters were determined. The physical characteristics of ZnO thin films were obtained by the analyses of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) to discuss the surfaces, cross section and crystallization of ZnO thin films. The voltage analysis were measured the open and load voltage by the measurement system. The optimal deposition parameters for ZnO thin films are substrate temperature of 300¢J, RF power of 75W, sputtering pressure of 9 mTorr and oxygen concentration of 60%, which were determined by physical characteristics and voltage analysis. The study employs a precise mass loading of 0.57g on the cantilever to increase the vibration amplitude. The vibration source from 1~150Hz was provided to the piezoelectric transducer, and then the experimental results were showed resonance frequency of 75Hz by oscilloscope. When the optimal thickness of ZnO films is 1.08£gm and vibration amplitude is 1.19mm, the open circuit voltage of the power generator is 5.25V.After rectifying and flitting with a capacitor of 33nF,the maximum power of 1.0£gW/cm2 was achieved with the load resistance of 5M£[.

The piezoelectric transducer for vibration-energy harvesting is constructed of a piezoelectric layer, bottom electrode and a top electrode. In order to obtain an appropriate transducer for the low-frequency operating; environmentally-friendly and long-term, the flexible substrate, the piezoelectric layer, and the additional mass-loading (tip mass) have been investigated thoroughly. This study investigates the feasibility of a high-performance ZnO and AlN based piezoelectric transducer for vibration-energy harvesting applications. Firstly, the piezoelectric transducer is constructed of a Cu/ZnO/ITO/PET structure. Both scanning electron microscopy and X-ray diffraction indicate that, among the favorable characteristic of the ZnO piezoelectric film include a rigid surface structure and a high c-axis preferred orientation. Hence, an open circuit voltage of 1.87 V for the ZnO piezoelectric transducer at a vibration frequency of 100 Hz is obtained by an oscilloscope. After rectifying and filtering, the output power of the generator exhibits an available benefit of 0.07 £gW/cm2 with the load resistance of 5 M£[. Secondly, this investigation introduces novel means of integrating high-performance piezoelectric transducers using single-sided ZnO and AlN films with a flexible stainless steel substrate (SUS304). Hence, the SUS304 substrate exhibits the long-term stability under vibration. The single-sided ZnO and AlN transducers are deposited on the SUS304 substrate at a temperature of 300 oC by an RF magnetron sputtering system. Scanning electron microscopy and X-ray diffraction of piezoelectric films reveal a rigid surface structure and a high c-axis-preferred orientation. A mass loading at the front-end of the cantilever is critical to increase the amplitude of vibration and the power generated by the piezoelectric transducer. The open circuit voltage of the single-sided ZnO power generator is 10.5 V. After rectification and filtering through a capacitor with a capacitance of 33 nF, the output power of the single-sided ZnO generators exhibited a specific power output of 1.0 £gW/cm2 with a load resistance of 5 M£[. Finally, this investigation fabricates double-sided piezoelectric transducers for harvesting vibration-power. The double-sided piezoelectric transducer is constructed by depositing piezoelectric thin films on both the front and the back sides of SUS304 substrate. The titanium (Ti) and platinum (Pt) layers were deposited using a dual-gun DC sputtering system between the piezoelectric thin film and the back side of the SUS304 substrate. Scanning electron microscopy and X-ray diffraction of piezoelectric films reveal a rigid surface structure and highly c-axis-preferring orientation. The maximum open circuit voltage of the double-sided ZnO power transducer is approximately 18 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.3 £gW/cm2 is obtained from the double-sided ZnO transducer with a load resistance of 6 M£[. The variation of the power output of ¡Ó0.001% is obtained after 24-hour continuous test. The maximum open circuit voltage of the double-sided AlN power transducer is approximately 20 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.462 £gW/cm2 is obtained from the double-sided AlN transducer with a load resistance of 7 M£[.

Icing on aircraft wings is one of the leading causes of aircraft crashes. It is mainly caused due to accumulation of ice or snow on the wing surface due to impact with supercooled droplets when passing through clouds at high altitudes, causing loss of lift obtained by the wings. It was found that droplet impact characteristics are dependent on droplet size, surface roughness, surface material hydrophobicity, and droplet impact velocity. As a continuation of the study of droplet impact contact characteristics by varying surface roughness and impact velocity, this study focuses on droplets impacting the vibrating surface at frequencies between 2-7 kHz. Atomization (water drop splitting into smaller droplets and ejecting from the surface) has been observed at different rates for all frequencies. The first set of data is collected by keeping roughness constant and increasing the amplitude of the vibration to observe the critical amplitude at which atomization is initiated. The surface roughness is varied for the second set of experiments. The data is quantified using image processing of the high-speed videos to obtain the rate of ejection for each case. / Master of Science / Icing on aircraft wings is among the leading causes of crashes, which involves small freezing water drops sticking to the wing surface thus reducing the lift. This study is an investigation to experimentally observe how small water droplets interact with surfaces vibrating at high frequencies when impacted. Surface roughness, materials, droplet velocities, and frequency of vibration have been varied and the droplet was captured using high-speed photography to study their effect on the aforementioned interaction. Glass, PET-G. and aluminum having specific roughness were fabricated using laser and chemical etching. Atomization (water drop splitting into smaller droplets and ejecting from the surface) has been observed at different rates for all frequencies. A relation between the amplitude of the vibration and the rate of atomization was found. The effect of varying frequencies and surface roughness has also been documented.

Aujourd’hui, avec l’envolée mondiale du prix du pétrole, la question énergétique est devenue un sujet d’importance et la possibilité d’exploiter l’énergie ambiante connaitun regain d’attention. Ainsi dans cette thèse, nous nous intéressons aux dispositifs de récupération d’énergie piézoélectrique de vibration dont l’objectif final est de réaliser un réseau de capteurs sans fil (WSN) autonome de faible consommation d’énergie. L’idée est dans un premier temps de prolonger la durée de vie de la batterie, puis dans un second temps de rendrele capteur totalement autonome d’un point de vu énergétique. Les dispositifs actuels étant basés sur la vibration d’une poutre (résonateur mécanique), ils ne sont efficaces qu’à la résonance, avec une faible bande-passante. Ainsi dans ce travail, nous avons tout d’abord proposé une technique de décalage de la fréquence de résonance à l’aide de capacités commutées, cette techniqueréalise un ajustement de la fréquence de résonance en fonction de la fréquence de la source d’excitation et ainsipermetune augmentation de la puissance de sortie. Cette technique a été implémentée avec succès sur un module de capteur WSN avec transmissiond’un signal RF. Toujours dans l’objectif d’agrandir la bande-passante, un résonateur hybride (piézoélectrique/magnétique) bistable associé à une interface électrique (SSHI) a été proposé.Cenouveau et intéressant concept de combiner le résonateur hybride avec une interface à commutation de la tension piézoélectrique a montré, à l’aide de résultats expérimentaux et de simulation,que la puissance est augmentée sur une large bande passante.De plus, afin de rendre le système totalement autonome et de commander les interrupteurs de l’interface électriqueaux instants optimaux, une technique de détection du passage par zéro de la vitesse de vibration a été proposée. Les résultats montrent de bonnes performancesde cette méthode sur toutes lesinterfaces et résonateurs.Contrairement à la méthode classique de détection de la tension crête, la détection du passage par zéro de la vitesse est plus précise. La récupération d’énergie piézoélectrique engendrant un amortissement de la source vibrante, il est possible d’utiliser les mêmes interfaces électriques pour réaliser l’amortissement semi-passif de vibrations de structures mécaniques. Il s’agit d’extraire le maximum d’énergie de la structure en vibration à l’aide de l’élément piézoélectrique. Ainsi, afin de rendre les interfaces électriques pour l’amortissement (SSHD) totalement autonomes, nous avons proposé d’associer la récupération d’énergie piézoélectrique à l’amortissement de structure. L’avantage majeur est qu’il est seulement nécessaire de sacrifier légèrementles performances de l’amortissement pour rendre le système totalement autonome. Les performances ainsi que les limites de cette technique ont été analysées. / Nowadays with the world oil price soaring, the energy issue is becoming a significant topic and the possibility of harvesting ambient energy receiving much attention. In this dissertation, the main topic surrounds improving the piezoelectric energy harvesting device in several aspects and the final objective is to integrate it with low power consumption device, for example a wireless sensor network (WSN) node to extend the battery lifetime and further supply the energy to device directly. Based on the high mechanical quality factor of the structure, the output power of the piezoelectric energy harvesting device will decrease rapidly when the exciting frequency is out of the resonant frequency range. The tunable resonant frequency technique is proposed to broaden the resonant frequency range and increase the output power effectively. Then this technique is successfully combined with a WSN module to transmit the RF signal. To broaden resonant frequency another method is proposed, based on a bistable vibrating cantilever beam and a switching-type interface circuit (SSHI). It's a new and interesting concept to combine these two techniques. The magnets are used to make mechanical behavior non-linear and increase the output power at non-resonance. The SSHI technique through zero-velocity detection can work well when system is driven in non-linear system. The experimental and simulation results through work-cycles discussion show good performance of combining these two techniques. In the interface circuit design, synchronized switching harvesting on an inductor (SSHI) have been verified a successful technique to increase output power in low-coupling system. In order to make use of the SSHI technique in the real application, the velocity control self-powered SSHI (V-SSHI) system is proposed. Unlike the conventional peak detector technique, the zero-velocity detection is used to make the switching time more accurate. The energy flow is separated into three paths to construct the V-SSHI and the experimental results show good performance. When the system is not low-coupled, the SSHI technique will damp vibration.This technique is called SSDI (synchronized switching damping on an inductor). Based on the self-powered technique and zero-velocity detection used in the V-SSHI, these techniques are further applied in structural damping to construct a self-powered SSDI (SP-SSDI). The major advantage is that it is only necessary to sacrifice a small amount of damping performance to make the system fully self-powered. The theoretical analysis and experiment results of time domain comparison and frequency response testing show the limit and performance of the SP-SSDI technique. The SP-SSDI system is a like a feedback loop system and when the displacement is over the limit the SP-SSDI will effectively damp the vibration.

O projeto de transdutores piezelétricos envolve modelagens matemáticas e verificações experimentais, que são necessárias para validá-los. Através das análises dos transdutores verificam-se as influências das condições de contorno experimentais e as dificuldades para modelá-las. No entanto, na literatura atual este ponto não é discutido de forma abrangente. Além disso, as propriedades elétricas, piezelétricas e mecânicas dos materiais devem ser conhecidas com precisão para que o modelo represente um transdutor físico. Estas propriedades são fornecidas pelos fabricantes em valores aproximados, porém algumas delas, como por exemplo, o amortecimento mecânico, não são fornecidas, o que dificulta a modelagem. Por estes motivos, este trabalho trata do desenvolvimento de técnicas de verificações experimentais de transdutores piezelétricos, visando esclarecer efeitos relacionados às variações nas condições de contorno devido à fixação de pequenos espelhos e a fixação do próprio transdutor num suporte, e propor formas de incorporar esses efeitos nos modelos matemáticos. Além disso, propõe-se uma metodologia para a determinação do coeficiente de amortecimento das cerâmicas piezelétricas. São apresentadas as técnicas ópticas utilizadas na medição dinâmica e estática de deslocamentos de transdutores piezelétricos, os problemas das influências mecânicas, como vibrações ambientes, nas análises ópticas e as respectivas soluções adotadas. As análises numéricas foram conduzidas com o software de elementos finitos ANSYS e os resultados comparados com as verificações experimentais. Os materiais analisados são piezocerâmicas PZT-5A, piezoatuadores flextensionais, projetados pelo método de otimização topológica e um piezoatuador bilaminar. Nos resultados apresentados são mostrados os desvios e os comentários sobre as possíveis causas. / Piezoelectric transducer design is done by using numerical method and experimental analysis, which are needed to validate it. Transducers analysis allow us to verify the influence of experimental boundary conditions and the difficulties to model them. However, in the current literature this point is not discussed in a comprehensive way. In addiction, electrical, piezoelectric and mechanical material properties must be known with accuracy, to represent a real transducer. Approximately values of these properties are provided by manufacturers, however other property values are not provided, such as for example, mechanical damping, which causes difficulties for modelling. Therefore, this work is about the development of experimental techniques to analyze piezoelectric transducers, aiming to understand the effects related to boundary conditions changes due to stick of small mirrors and the way the transducer is held, and suggest of way to incorporate these effects in mathematical model. In addiction, suggests a methodology to determine the piezoceramics damping coefficient. It is described optical techniques used for displacement measurements of piezoelectric transducer in dynamic and static operation, problems related to mechanical influences in optical analysis, such as environment vibration, and respective applied solutions. Numerical analysis are conducted by using finite element software, ANSYS, and the results are compared with experimental verification. The materials analyzed are piezoceramic PZT-5A, flextensional piezoactuators, designed by using topology optimization and a bimorph pizoactuator. In the present results is shown the deviation and comments about possible cause.

Este trabalho teve por objetivo desenvolver e caracterizar um conjunto transdutor piezelétrico de potência e pinça laparoscópica para cortes homeostáticos, o qual constitui parte fundamental do projeto do Bisturi Ultrassônico Nacional. O transdutor, do tipo Langevin, é composto por quatro cerâmicas piezelétricas que convertem energia elétrica em deslocamento mecânico. Um componente importante do transdutor é o amplificador mecânico, cuja finalidade é aumentar a amplitude do deslocamento. O transdutor e o amplificador foram desenvolvidos através de um modelo axissimétrico de elementos finitos implementado no software ANSYS e a lâmina foi desenvolvida através de um modelo tridimensional em elementos finitos. Para cada associação, entre os componentes, os resultados numéricos da resposta em frequência da impedância elétrica e do coeficiente de acoplamento eletromecânico, foram comparados com os resultados experimentais. Também foi desenvolvido um mecanismo inovador de acionamento da pinça laparoscópica. O resultado desta pesquisa proporcionou uma inovação tecnológica na área médica, contribuindo assim para o progresso tecnológico do país. / The aim of this work was to develop and characterize a high power piezoelectric transducer coupled to a laparoscopic forceps for homeostatic cuts, which is a fundamental part of the National Ultrasonic Scalpel Project. The Langevin type transducer consists of four piezoelectric ceramics that convert electrical energy into mechanical displacement. An important component of the transducer is the mechanical amplifier, which increases the amplitude of displacement. The transducer and amplifier have been developed through an axisymmetric finite element model, implemented in ANSYS, and the blade was developed using a three-dimensional finite element model. For each association between the components, the numerical results of the frequency response of the electrical impedance and electromechanical coupling coefficient were compared with the experimental results. An innovative drive mechanism was developed for the laparoscopic forceps. The result of this research provided a technological innovation in the medical field, thus contributing to the technological progress of the country.

<p>Implantable biomedical devices have been widely used to treat a variety of diseases for many decades. If allowed by the size and form factor, batteries have been the power source of choice in implantable devices (e.g., cardiac pacemakers). Batteries are, however, still big and come in shapes that are not ideal for minimally invasive deployment. Inductive powering is another commonly used energy source in which two well-aligned coils allow a transmitter to power the implanted receiver (e.g., cochlear implants). Once the receiver coil becomes small (mm-scale), the inductive powering link becomes very inefficient and sensitive to slight misalignment between the coils. Hence, it becomes increasingly difficult to power small devices implanted deep (>5 cm) within the tissue using inductive powering. Ultrasonic powering is an attractive alternative for powering miniature devices since it can penetrate deep into the tissue, it has greater efficiency at mm-scale receiver size, it can be omni-directional, and it is more amenable to miniaturization.</p> <p>In this dissertation, I describe the use of ultrasonic waves to power and control mm-scale implantable devices. After a detailed look at ultrasonic transmission link, I will discuss factors affecting the power transfer efficiency. These include the effect of receiver aspect ratio and size on the resonant frequency and factors related to acoustic and electrical matching. A 3D printed acoustic matching layer in then described. I will discuss two applications using ultrasound to power and control implantable devices. The first is a low-power on-off acoustic control scheme to reduce the standby power consumption in implantable devices. The second is an ultrasonically powered electrolytic ablator with an on-board micro-light-source for the treatment of cancer.</p>

Este trabalho apresenta um estudo do processo de corte de pequenas placas de piezocerâmicas usadas na fabricação de materiais piezocompósitos pelo processo de corte e preenchimento. Foi feito o projeto de uma máquina de corte com disco adiamantado de acordo com as necessidades do processo de corte e preenchimento para produzir piezocompósitos que requerem cortes tão finos quanto 30µm. A máquina utiliza um \"spindle\" com mancais aerostáticos com rotação de até 60.000 rpm para cortes com lâminas de 2 polegadas de diâmetro. Os piezocompósitos são os elementos principais na fabricação de transdutores de ultra-som, com freqüências até 10 MHz, para aplicações médicas e industriais. O estudo do corte com discos adiamantados com pequenas espessuras é baseado no modelo cinemático usado para modelar o processo de retífica por abrasão e em verificações experimentais de corte de pequenas placas de piezocerâmicas. Os resultados experimentais do corte de piezocerâmica tipo PZT com disco adiamantado são analisados com o auxílio de um microscópio óptico. São medidas as imperfeições superficiais dos cortes. / This work presents a study of the diamond blade dicing of piezoceramic slabs to fabricate piezocomposites by dicing and fill process. A diamond blade dicing machine is designed according the needs of the dicing and fill process to produce piezocomposites which requires dicing with diamond blades as thin as 30µm. The dicing machine has a high speed (up to 60.000 rpm) spindle with aerostatic bearings for 2 inches diameter dicing blades. The piezocomposites with frequency up to 10 MHz are the main part of ultrasonic transducers for medical and industrial applications. The study of thin diamond blade dicing is based in the kinematic model for grinding and experimental work. The results of diamond blade dicing of PZT piezoceramic slabs are analysed with an optical microscope and the measurements of superficial cracks are presented.