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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

A Design Procedure for Flapping Wings Comprising Piezoelectric Actuators, Driver Circuit, and a Compliant Mechanism

Chattaraj, Nilanjan January 2015 (has links) (PDF)
Flapping-wing micro air vehicle (MAV) is an emerging micro-robotic technology, which has several challenges toward its practical implementation. Inspired by insect flight, researchers have adopted bio-mimicking approach to accomplish its engineering model. There are several methods to synthesize such an electromechanical system. A piezoelectric actuator driven flapping mechanism, being voltage controlled, monolithic, and of solid state type exhibits greater potential than any conventional motor driven flapping wing mechanism at small scale. However, the demand for large tip deflection with constrained mass introduces several challenges in the design of such piezoelectric actuators for this application. The mass constraint restricts the geometry, but applying high electric field we can increase the tip deflection in a piezoelectric actuator. Here we have investigated performance of rectangular piezo-actuator at high electric field. The performance measuring attributes such as, the tip deflection, block force, block moment, block load, output strain energy, output energy density, input electrical energy, and energy efficiency are analytically calculated for the actuator at high electric field. The analytical results suggest that the performance of such an actuator can be improved by tailoring the geometry while keeping the mass and capacitance constant. Thereby, a tapered piezoelectric bimorph cantilever actuator can provide better electromechanical performance for out-of-plane deflection, compared to a rectangular piezoelectric bimorph of equal mass and capacitance. The constant capacitance provides facility to keep the electronic signal bandwidth unchanged. We have analytically presented improvement in block force and its corresponding output strain energy, energy density and energy effi- ciency with tapered geometry. We have quantitatively and comparatively shown the per- formance improvement. Then, we have considered a rigid extension of non-piezoelectric material at the tip of the piezo-actuator to increase the tip deflection. We have an- alytically investigated the effect of thick and thin rigid extension of non-piezoelectric material on the performance of this piezo-actuator. The formulation provides scope for multi-objective optimization for the actuator subjected to mechanical and electrical con- straints, and leads to the findings of some useful pareto optimal solutions. Piezoelectric materials are polarized in a certain direction. Driving a piezoelectric actuator by high electric field in a direction opposite to the polarized direction can destroy the piezo- electric property. Therefore, unipolar high electric field is recommended to drive such actuators. We have discussed the drawbacks of existing switching amplifier based piezo- electric drivers for flapping wing MAV application, and have suggested an active filter based voltage driver to operate a piezoelectric actuator in such cases. The active filter is designed to have a low pass bandwidth, and use Chebyshev polynomial to produce unipolar high voltage of low flapping frequency. Adjustment of flapping frequency by this voltage driver is compatible with radio control communication. To accomplish the flapping-wing mechanism, we have addressed a compatible dis- tributed compliant mechanism, which acts like a transmission between the flapping wing of a micro air vehicle and the laminated piezoelectric actuator, discussed above. The mechanism takes translational deflection at its input from the piezoelectric actuator and provides angular deflection at its output, which causes flapping. The feasibility of the mechanism is investigated by using spring-lever (SL) model. A basic design of the com- pliant mechanism is obtained by topology optimization, and the final mechanism is pro- totyped using VeroWhitePlus RGD835 material with an Objet Connex 3D printer. We made a bench-top experimental setup and demonstrated the flapping motion by actuating the distributed compliant mechanism with a piezoelectric bimorph actuator.
52

Caracterização de uma microválvula fabricada usando o polímero piezoelétrico poli(fluoreto de vinilideno) (PVDF) integrada a saída de um microbocal sônico / Characterization of a microvalve using the piezoelectric polymer poly(viniyidene fluoride) (PVDF) integrated to a micronozzle end

Rodrigo Sérgio Wiederkehr 17 December 2007 (has links)
Este trabalho descreve a seqüência de fabricação de uma microválvula piezoelétrica posicionada na saída de um microbocal sônico. A técnica usada para fabricar os microbocais foi o jateamento utilizando pó de alumina e o substrato usado foi de vidro. As microválvulas são atuadores fabricados com o polímero poli(fluoreto de vinilideno) (PVDF) que é um material piezoelétrico. Os microbocais têm um formato convergente-divergente com diâmetro na entrada de 1 mm e com diâmetro na garganta em cerca de 240 microns. O atuador foi fabricado no modo bimorfo (duas folhas do polímero coladas com polarização opostas) com dimensões de 3 mm de largura por 6 mm de comprimento. Ambas as folhas do polímero são recobertas por um filme condutor de 200 nm de espessura usados como eletrodos. Aplicando uma voltagem entre os eletrodos uma folha expande enquanto a outra contrai gerando um movimento vertical do atuador. O movimento vertical pode ser maior ou menor dependendo do valor da tensão aplicada. Os dispositivos foram testados usando uma linha de gás, aplicando tensões DC e AC nos eletrodos do atuador. Para controle, também foram realizadas medidas em bocais sem atuadores. No caso onde foram aplicadas tensões DC nos atuadores, a pressão de entrada foi constante de 266 Pa. Aplicando uma tensão de +300 V DC nos eletrodos, o atuador teve um movimento vertical na direção oposta ao do microbocal de 20 microns (movimento de abertura). Neste caso o fluxo de gás medido, quando a razão de pressão entre a entrada e a saída atingiu 0,5, foi de 150 cm3/min. Aplicando uma tensão de -300 V DC (o que significa um movimento vertical de fechamento de 13 microns), o fluxo de gás medido, quando a razão de pressão foi de 0,5, foi de 134 cm3/min. Assim, existe uma faixa de fluxo entre 134 cm3/min e 150 cm3/min que pode ser controlada através do atuador. Em uma das medidas onde se aplicou uma tensão AC (200 V com 5 Hz de freqüência), foi utilizada uma pressão de entrada 13300 Pa. Neste caso, para uma razão de pressão de 0,5, onde o bocal se encontrava blocado, foi observado um fluxo de 847 cm3/min. Considerando que o fluxo do bocal sem atuador, nas mesmas condições de medida foi de 614 cm3/min, concluímos que o dispositivo no modo AC funciona como uma microbomba. A relevância deste trabalho está a utilização do poli(fluoreto vinilideno) (PVDF) na fabricação de um atuador para uso como microválvula. Este material que ainda não havia sido testado para esta finalidade. A fabricação dos microbocais foi feita em um substrato de vidro usando a técnica de jateamento também é inédita. Esta técnica é bastante usada na fabricação de microestruturas na superfície do vidro. Mas nunca tinha sido usada para a fabricação de microbocais que são canais em formato cônico que atravessam o substrato. / This work describes the fabrication and test of a microvalve integrated in a micronozzle. The technique used to fabricate the micronozzles was powder blasting using aluminum oxide powder and glass as substrate. The microvalves are actuators made from PVDF (poli(vinylidene fluoride)), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with diameter of 1mm at the entrance and throat around 240µm. The actuators were fabricated as a bimorph structure (two piezoelectric sheets were clamped together with opposite polarization) with dimensions 3 mm width and 6 mm length. Both sheets are recovered with a conductive thin film with 200 nm of thickness used as electrodes. Applying voltage between the electrodes one sheet expands while the other contracts and this generate a vertical movement to the entire actuator. If the voltage is changed, this movement can be higher or lower. The devices were tested in a gas line applying DC and AC voltages between the actuator\'s electrodes. Measurements were also realized using a micronozzle without actuator, for control. In the case where DC voltage was applied between the actuators electrodes, the inlet pressure was kept constant in 266 Pa. Applying +300V DC voltage between the electrodes, the actuator moved 20µm vertically in the opposite direction of the micronozzle (it opened). In this case the volume flux rate, for a pressure ratio (outlet / inlet) of 0.5, was 150 cm3/min. Applying -300V DC between the electrodes (that means it closed 13 microns in the micronozzle direction), for a pressure ratio of 0.5, the volume flux rate was 134 cm3/min. With these results, we conclude that it is possible to control the flow through the device in the range between 134 and 150 cm3/min. Flow measurements were also performed applying AC voltage (200V AC with frequency of 5 Hz) between the actuator electrodes and with the inlet pressure kept constant in 13300 Pa. In this case, with a pressure ratio (outlet / inlet) of 0.5, blocking the micronozzle, the flow rate measured was 847 cm3/min. Considering that the flow rate measured for the micronozzle without actuator was 614 cm3/min, in the same measurement conditions, we concluded that the device, in AC mode, was working as a micropump. The relevance of this work was the use of the poly(vinylidene) (PVDF) in the fabrication of the actuators and use it as a microvalve. The micronozzles were fabricated in a glass substrate using the powder blasting technique that was also new.
53

Recherche, développement et réalisation d'un contrôleur de Fabry-Perot de nouvelle génération / Research, development and realization of a new generation Fabry-Perot controller

Ouattara, Issa 25 June 2015 (has links)
L’équipe Physique des Galaxies du Laboratoire d’Astrophysique de Marseille a développé un nouveau type d'interféromètre de Fabry-Perot, équipé de trois actionneurs piézoélectriques amplifiés et de trois capteurs capacitifs permettant le contrôle de l'espacement et du parallélisme des lames de verres de l'ordre de 200 µm avec une précision de positionnement du nm.L'objectif visé de ce manuscrit, composé de 3 parties, est le pilotage de cet interféromètre. La première partie, composée des chapitres 1 et 2, présente les généralités sur l'interférométrie de Fabry-Perot puis décrit les instruments 3DNTT et BTFI où seront installés l'interféromètre de nouvelle génération et son contrôleur associé. La conception et la réalisation d'un amplificateur hybride en vue de la réduction des non-linéarités des actionneurs piézoélectriques mettent fin à cette partie.La deuxième partie, chapitres 3 et 4, décrit le développement et la réalisation du contrôleur. Pour cela, une démarche basée sur le concept du Co-design a été adoptée.Le contrôleur ainsi réalisé est composé d'une carte de développement Microzed dont le cœur est un système sur puce de la série Zynq 7000 EPP et d'une carte d'interfaçage comportant des convertisseurs 3 ADC et 3 DAC et des circuits d'alimentation. La troisième et dernière partie, chapitres 5 et 6, traite de la modélisation d'état de l’interféromètre de Fabry-Perot et de son contrôle : un contrôle classique basé sur la régulation PID et un contrôle robuste et optimal basé sur le filtrage de KALMAN. Cette dernière partie conclut sur les perspectives pouvant découler des contributions de ce travail sur le contrôle et la commande Fabry-Perot. / The Physics of Galaxies Team of Laboratoire d'Astrophysique de Marseille (LAM) has developed a new type of Fabry-Perot, with three amplified piezoelectric actuators and three capacitive sensors to control the spacing and parallelism of mirror plates of approximately 200 µm with a positioning accuracy of 3 nm.The purpose of this manuscript, consisting of 3 parts is the control of this interferometer.The first part, consisting of Chapters 1 and 2 presents the general interferometry Fabry-Perot and then describes 3DNTT and BTFI instruments which will be installed the next generation interferometer and its associated controller. The design and implementation of a hybrid amplifier to reduce non-linearities of the piezoelectric actuators (hysteresis and creep) end this first part.The second part, Chapters 3 and 4, describes the development and implementation of the controller.For this, an approach based on codesign concept was adopted. The thus achieved controller consists of a Microzed development board whose heart is a system on chip of the 7000 series Zynq EPP (FPGA + Dual-Core ARM Cortex A9) and an interface card with converters (3 ADC and 3 DAC) and power supply circuits.For the finalization of the controller, two steps are necessary: hardware design in Xilinx Vivado and software design in Xilinx SDK.The third and final section, chapters 5 and 6 deals with the Fabry-Perot space-state modeling and its control: a classic control based on PID control and a robust and optimal control based on KALMAN filtering. This last part concludes the outlook may result from contributions of this work on the monitoring and control of the Fabry-Perot.
54

[pt] IDENTIFICAÇÃO NÃO LINEAR CAIXA-PRETA DE SISTEMAS PIEZOELÉTRICOS / [en] NONLINEAR BLACK-BOX IDENTIFICATION OF PIEZOELECTRIC SYSTEMS

MATHEUS PATRICK SOARES BARBOSA 10 September 2021 (has links)
[pt] Atuadores baseados em materiais piezelétricos apresentam características ideais para aplicações como transmissão acústica e micromanipulação. No entanto, não-linearidades inerentes a estes atuadores, como histerese e fluência, aumentam o desafio de controla-los. Além disso, a crescente necessidade de atuadores mais precisos e rápidos aliada a frequentes mudanças nas condições ambientais e operacionais agravam ainda mais o problema. Modelagens analíticas são específicas ao sistema ao qual foram feitas, o que significa que elas não são facilmente escalonáveis e eficientes para todos os tipos de sistemas. Adicionalmente, com o aumento da complexidade, os fenômenos que regem a física do sistema não são totalmente conhecidos, tornando difícil o desenvolvimento destes modelos. Este trabalho investiga esses desafios do ponto de vista da metodologia de identificação de sistemas e modelos baseados em dados para atuadores piezelétricos. A abordagem de modelagem caixa preta foi testada com dados experimentais adquiridos em um ambiente de laboratório para os estudos de caso de micromanipulação e transmissão acústica. Sinais de uso geral foram empregados como entrada de excitação do sistema de modo a acelerar a aquisição e estimação dos parâmetros. Parte dos modelos desenvolvidos foram validados com um conjunto de dados separado. Em ambos os casos foi necessário pré-processamento para otimização da quantidade de dados. Os modelos testados incluem a Média Móvel AutoRegressiva com entradas eXógenas (ARMAX), AutoRegressiva Não Linear com entradas eXógenas (NARX) com uma estrutura de rede neural artificial e Média Móvel AutoRegressiva Não Linear com entradas eXógenas (NARMAX). Os resultados mostram uma boa capacidade de prever as não-linearidades do micro manipulador e, portanto, a histerese em diferentes frequências de entrada. O sistema de transmissão acústica foi modelado com sucesso. Embora os resultados mostrem que ainda há espaço para melhorias, eles fornecem informações importantes sobre possíveis otimizações para o sistema uma vez que os modelos apresentados são uteis para janelas de predição curtas. / [en] Actuators based on piezoelectric materials have ideal characteristics for applications such as acoustic transmission and micromanipulation. However, the inherent nonlinearities of those actuators, such as hysteresis and creep, greatly increase the challenge to control such devices. Furthermore, the increasing need for more precise and faster actuators, allied with frequent changes in the environmental and operational conditions, further worsens the problem. Analytical models are application-specific, meaning that they are not easily and efficiently scalable to all systems. Also, with increased complexity, the understating of underlying phenomena is not fully documented, making it difficult to develop such models. This work investigates those challenges from the perspective of the system identification methodology and data-driven models for piezoelectric actuators. The black-box approach is tested with experimental data acquired in a laboratory setting for micromanipulator and acoustic transmission case studies. In some datasets, general-purpose signals were employed as the excitation input of the system to accelerate the data acquisition of the whole system dynamic and estimation process. Additionally, some models were validated on a separate dataset. In both cases, preprocessing was employed to optimize the amount of data. The tested models include the AutoRegressive Moving Average with eXogenous inputs (ARMAX), Nonlinear AutoRegressive with eXogenous inputs (NARX) with an artificial neural network structure, and Nonlinear AutoRegressive Moving Average with eXogenous inputs (NARMAX). The results show a good ability to predict the nonlinearities of the micromanipulator and, therefore, the hysteresis at different input frequencies. The acoustic transmission system was successfully modeled. Although the results show that there is still room for improvements, it provides insights into possible optimizations for the setup as the models here devised are useful for short prediction windows.
55

Design and Development of Piezoelectric Stack Actuated Trailing Edge Flap for Helicopter Vibration Reduction

Mallick, Rajnish January 2014 (has links) (PDF)
This research investigates on-blade partial span active plain trailing edge flaps (TEFs)with an aim to alleviate the helicopter vibrations. Among all the available smart materials, piezoelectric stack actuator(PEA)has shown its strong candidature for full scale rotor systems. Although, PEAs are quite robust in operation, however, they exhibit rate dependent hysteresis phenomenon and can generate only very small displacements. Dynamic hysteresis is a complex phenomenon which, if not modeled, can lead to drift in the vibration predictions. In this research, a comprehensive experimental analysis is performed on a commercially available piezostack actuator, APA-500L, which is well suited for full scale applications. Rate dependent hysteresis loops are obtained for helicopter operational frequencies. Nonlinear rate-dependent hysteresis loops are modeled using conic section approach and the results are validated with experimental data. Dynamic hysteresis exhibited by the PEA is further cascaded with the helicopter aeroelastic analysis and its effect on helicopter vibration predictions is investigated. PEAs generate high force but are limited by small translational motions. A linear to rotary motion amplification mechanism is required to actuate the TEF for vibration alleviation. A smart flap is designed and developed using computer-aided-design models. A rotor blade test section is fabricated and a lever-fulcrum mechanism (AM-1) is developed for a feasibility study. Smart flap actuation is demonstrated on the rotor blade test section. The conventional motion amplification devices contain several linkages, which are potential sites for structural failure. A novel pinned-pinned post-buckled beam linear-to-rotary motion amplifier (AM-2) is designed and developed to actuate the flaps. A new design of linear-to-linear amplification mechanism (LX-4) is developed and is employed in conjunction with AM-2 to increase the flap angles by an order of magnitude. An analytical model is developed using Mathieu-Hill type differential equations. Static and dynamic tests are conducted on a scaled flap model. Helicopter aeroelastic simulations show substantial reduction in hub loads using AM-2 mechanism. To further enhance the flap angles, an optimization study is performed and optimal beam dimensions are obtained. A new technique is also proposed to actively bias the flaps for both upward and downward motion. Critical flap design parameters, such as flap span, flap chord and flap location influences the flap power requirement and vibration objective function significantly. A comprehensive parametric investigation is performed to obtain the best design of TEFs at various advance ratios. Although, parametric study equips the designer with vital information about various critical system parameters, however, it is a computationally expensive exercise especially when used with large comprehensive helicopter aero elastic codes. A formal optimization procedure is employed to obtain the optimal flap design and location. Surrogate models are developed using design of experiments based on response surface methodology. Two new orthogonal arrays are proposed to construct the second order polynomial response surfaces. Pareto analysis is employed in conjunction with a newly developed computationally efficient evolutionary multi-objective bat algorithm. Optimal flap design and flap locations for dual trailing edge flaps are obtained for mutually conflicting objectives of minimum vibration levels and minimum power requirement to actuate the flaps.
56

Investigating the Application and Sustained Effects of Stochastic Resonance on Haptic Feedback Sensitivity in a Laparoscopic Task

Wilcox, Kara Liane 08 June 2023 (has links)
No description available.

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