Piezoelectric composites have been investigated for use in a variety of areas, including flow control, structural control, energy harvesting, and fuel ignition systems. While many of the investigations conducted in these areas have utilized traditional piezo actuation systems, such as unimorphs or stack actuators, a growing number of research groups are examining the increased performance derived from the mechanical advantage, and enhanced domain rotation, found in prestressed unimorph designs. Prestressed devices, like Thunder® and LIPCA, have been shown well suited for a number of applications; however, the price associated with these devices can often prevent them from being implemented. In an effort to produce a low cost unimorph device that possesses a performance-enhancing curved form, the present investigation presents a novel technique for manufacturing prestressed piezoelectric actuators that are capable of meeting the same high displacement and load bearing capabilities exhibited by conventional prestressed devices. The newly proposed mechanically prestressed composite device, or MPC, is similar in form and function to well-documented thermally prestressed devices like Thunder®. However, rather than deriving its characteristic curved form from a thermally induced stress, the present class of devices relies on the resorting force incited in the piezoelectric ceramic upon adhesion to a mechanically deformed substrate to provide both the performance-enhancing prestress and final form of the device. To aid in refinement of the newly proposed design, beam theory was used to model the stress developed within the device. The model allowed designers to investigate the limitations imposed on the performance-enhancing curved form of the device by the stresses developed in the ceramic as a result of the curvature. Findings derived from the model were experimentally verified before a finalized design was specified for the composite, and a number of devices were manufactured. An initial characterization of the device was carried out based on the composite's response to mechanical and electrical loading. By determining the slope of the electrically and mechanically induced displacement response of the device, the investigation was able to define the center displacement constant and effective spring constant of the unimorph. These parameters not only allow designers to predict the displacement that will occur in response to a given electric field or tensile load, but also to allow for comparison with various devices. In the present investigation, the performance characteristics of mechanically prestressed composites were assessed as a function of substrate thicknesses and adhesive properties. With composites constructed using substrates approximately 9.2cm in length, devices were found to have typical center displacement constants on the order of 1.59 to 7.78kV/mm2 while retaining an effective stiffness between 4.5 to 7.5N/mm. These values were found to be similar to the .71 to 3.85kV/mm2 center displacement constants demonstrated by similarly sized and shaped Thunder® devices, which posses an effective stiffness in the range of 10 to 16.3N/mm. A comprehensive presentation of the test methods and procedures used to determine these values, along with other performance characteristics, are provided.

In this study, a modified two-dimensional axisymmetric finite element model is used to analyze the deflections of the piezoelectric actuator of valveless micropump after being driven by applied voltage. And the volume change of the pump chamber caused by the deformation of the piezoelectric actuator is calculated. We expect these analyses will help the design of piezoelectric valveless micropump. This model is able to analyze the piezoelectric materials which can transform the mechanical energy to electric energy and vice versa by properly assuming the three displacement fields and including the electrical potential as the fourth degree of freedom. Comparisons of some examples are made between the present work and those available in the literature to validate the exactitude and the feasibility of the present work. Furthermore, the inspections of the variations of the deflections will be carried out by changing the geometrical dimensions of the piezoelectric actuators under the same driven voltage.

This thesis deals with the design and experimental validation of Deformable Mirror Electronics (DME) for Extremely Large Telescope (ELT) Adaptive Optics (AO) applications. Modern ground based telescopes achieve their best possible imaging resolution through the application of AO. However, due to the fundamental diffraction of optical elements, the next generation of ELTs will employ primary mirrors of an increasingly large diameter as the final means of improving imaging resolution further. The corresponding increase in diameter and actuator count of the Deformable Mirrors (DMs) in these systems has led to the rapid development of high order DM technology. A significant challenge to operating these multi-thousand channel DMs is related to the DM Electronics (DME), which are required to be highly efficient so-as to operate within practical budgetary constraints. This thesis develops a DME reference design based on the requirements for the Thirty Meter Telescope’s next generation AO system, the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which operates two DMs with a total of 7673 piezoelectric actuators. The basis of the DME is the DM actuator driver, which has been developed to be suitable for very high order reproduction by optimization of its size, power, cost and reliability. A complication is that the piezoelectric actuators in NFIRAOS DMs require high voltage drive signals of ±400 V to obtain the rated stroke and must be current limited to avoid damage. Candidate amplifiers are evaluated in simulation and hardware based on a combination of performance, physical and functional criteria; with the most suitable circuit chosen for a multi-channel prototype implementation and testing with a DM breadboard prototype. The development and optimization of an amplifier capable of meeting NFIRAOS performance criteria and budgetary constraints is demonstrated. / Graduate / 0544 / 0606

With the ability to generate fine displacements with a resolution down to sub-nanometers, piezoelectric actuators (PEAs) have found wide applications in various nano-positioning systems. However, existence of various effects in PEAs, such as hysteresis and creep, as well as dynamics can seriously degrade the PEA performance or even lead to instability. This raises a great need to model and control PEAs for improved performance, which have drawn remarkable attention in the literature. Sliding mode control (SMC) shows its potential to the control of PEA, by which the hysteresis and other nonlinear effects can be regard as disturbance to the dynamic model and thus rejected or compensated by its switching control. To implement SMC in digital computers, this research is aimed at developing novel discrete models and discrete SMC (DSMC)-based control schemes for PEAs, along with their experimental validation. The first part of this thesis concerns with the modeling and control of one-degree of freedom (DOF) PEA, which can be treated as a single-input-single-output (SISO) system. Specifically, a novel discrete model based on the concept of auto-regressive moving average (ARMA) was developed for the PEA hysteresis; and to compensate for the PEA hysteresis and improve its dynamics, an output tracking integrated discrete proportional-integral-derivative-based SMC (PID-SMC) was developed. On this basis, by making use of the availability of PEA hysteresis models, two control schemes, named “the discrete inversion feedforward based PID-SMC” and “the discrete disturbance observer (DOB)-based PID-SMC”, were further developed. To illustrate the effectiveness of the developed models and control schemes, experiments were designed and conducted on a commercially available one-DOF PEA, as compared with the existing ones. The second part of the thesis presents the extension of the developed modeling and control methods to multi-DOF PEAs. Given the fact that details with regard to the PEA internal configurations is not typically provided by the manufacturer, a state space model based on the black box system identification was developed for the three-DOF PEA. The developed model was then integrated in the output tracking based discrete PID-SMC, with its effectiveness verified through the experiments on a commercially available three-DOF PEA. The superiority of the proposed control method over the conventional PID controller was also experimentally investigated and demonstrated. Finally, by integrating with a DOB in the discrete PID-based SMC, a novel control scheme is resulted to compensate for the nonlinearities of the three-DOF PEA. To verify its effectiveness, the discrete DOB based PID-SMC was applied in the control experiments and compared with the existing SMC. The significance of this research lies in the development of the discrete models and PID-based SMC for PEAs, which is of great help to improve their performance. The successful application of the proposed method in the control of multi-DOF PEA allows the application of SMC to the control of complicated multi-inputs-multi-outputs (MIMO) systems without details regarding the internal configuration. Also, integration of the inversion based feedforward control and the DOB in the SMC design has been proven effective for the tracking control of PEAs.

Piezoelectric effect was discovered in the 19th century, but the applications of piezoelectric effect were realized until the 20th century. In this paper, piezoelectric actuators, which are made based on piezoelectric effect, are employed to establish a three-degree-of-freedom micro-manipulator. The mechanism of this micro-manipulator is designed as a parallel-type mechanism. The kinematics of the micro-manipulator is also analyzed. In addition, a remote control framework is implemented with a control system and this achievement can be a demonstration for future feasibility of application of this micro-manipulator to robotic systems.

Bearings today need to be able to run at very high speed, providing high positional accuracy for the structure that it supports, and requiring very little or no maintenance. For this to happen, bearings must have tight tolerances and very low or zero friction during operation. This pushes many traditional contact-type bearings to their limits as they often fail due to friction, generating heat and causing wear. By comparison, existing non-contact bearings fare better because of their very low or zero friction. But some have their own problem too. For example, the fact that aerostatic bearings require an air supply means having to use a separate air compressor and connecting hoses. This makes the installation bulky. Aerodynamic and hydrodynamic bearings cannot support loads at zero speed. Both hydrodynamic and hydrostatic bearings may cause contamination to the work-pieces and the work environment because of the use of lubricating fluid. A potential solution to the above-mentioned problems is the new squeeze film air bearing. It works on the rapid squeeze action of an air film to produce separation between two metal surfaces. This has the benefit of being compact with a very simple configuration because it does not require an external pressurized air supply, can support loads at zero speed and is free of contamination. For this research, two squeeze film air journal bearings, made from material of Al 2024 - T3 and Cu - C101 with the same geometry, were designed. The bearing is in the shape of a round tube with three fins on the outer surface and the journal, a round rod. When excited at a certain normal mode, the bearing shell flexes with a desirable modal shape for the squeeze film action. The various modes of vibration of Al bearing were obtained from a finite-element model implemented in ANSYS. Two Modes, the 13th and 23rd, at the respective frequencies of 16.320 kHz and 25.322 kHz, were identified for further investigation by experiments with respect to the squeeze film thickness and its load-carrying capacity. For Cu bearing, the two Modes are also 13th and 23rd at the respective frequencies of 12.184 kHz and 18.459 kHz. In order to produce dynamic deformation of the bearings at their modes, a single layer piezoelectric actuator was used as a driver. The maximum stroke length and the maximum blocking force of the single layer piezoelectric actuator were determined using manual calculation and ANSYS simulation. In the coupled-field analysis, the single layer piezoelectric actuator was mounted on the outside surface of the bearing shell and loaded with an AC and a DC voltage in order to produce the static and dynamic deformation. For the static analysis, the maximum deformation of Al bearing shell is 0.124 μm when the actuators are driven at the DC of 75 V. For the dynamic analysis, the actuators are driven at three levels of AC, namely 55, 65 and 75V with a constant DC offset of 75V and the driving frequency coincided with the modal frequency of the bearing. The maximum dynamic deformation of Al bearing shell is 3.22μm at Mode 13 and 2.08μm at Mode 23 when the actuators were driven at the AC of 75 V and the DC of 75 V. Similarly, the FEA simulation was used for analyzing Cu bearing. Furthermore, the dynamic deformation of both Al and Cu bearing at Mode 13 and 23 are validated by experiments. This research developed two theoretical models that explain the existence of a net pressure in a squeeze film for the levitation. The first model uses the ideal gas law as first approximation whilst the second uses the CFX simulation to provide a more exact explanation. In terms of the load-carrying capacity, Mode 13 was identified to be better than Mode 23 for both bearings. However, at Mode 13, Al bearing has a higher load-carrying capacity than Cu bearing. This is due to Al bearing having a higher modal frequency and amplitude. Finally, the coupled-field analysis for fluid solid interaction (FSI) was studied at both Mode 13 and 23 for Al bearing. The findings are that: a) the fluid force in the squeeze film can affect the dynamic deformation of the bearing shell, especially at high oscillation frequency, more at Mode 13 than at Mode 23 due to the relatively high pressure end-leakage in the latter; b) the dynamic deformation of the bearing shell increases with the gap clearance in a logarithmic manner at Mode 13; and c) the micron levels of gap clearance provide a damping effect on the dynamic deformation of the bearing shell at Mode 13 and at Mode 23, though much less dominant.

The Equipment Controls and Electronics section (EN-STI-ECE) at CERN is developing a high precision piezo-actuated rotational stage for the UA9 crystal collimation project. This collaboration is investigating how tiny bent crystals can help to steer particle beams used in modern hadron colliders such as the Large Hadron Collider (LHC). Particles are deflected by following the crystal planar channels, "channeling" through the crystal. For high energy particles the angular acceptance for channeling is very low, demanding for a high angular precision mechanism, i.e. the rotational stage. Several control-related issues arising from the complexity and operational environment of the system make it difficult to design a controller that achieves the desired performance. This thesis investigates different control approaches that could be used to improve the tracking capability of the rotational stage. It shows that the IRC method could be used to efficiently control the rotational stage. Moreover it shows that a harmonic cancellation method could be used to increase the tracking accuracy by canceling known harmonic disturbances. The harmonic cancellation method (the RFDC) was implemented in this thesis and proposed as an add-on to the present control algorithm.

Flow control can lead to saving millions of dollars in fuel costs each year by making an aircraft more efficient. Synthetic jets, a device for active flow control, operate by introducing small amounts of energy locally to achieve non-local changes in the flow field with large performance gains. These devices consist of a cavity with an oscillating diaphragm that divides it, into active and passive sides. The active side has a small opening where a jet is formed, whereas and the passive side does not directly participate in the fluidic jet.Research has shown that the synthetic jet behavior is dependent on the diaphragm and the cavity design hence, the focus of this work. The performance of the synthetic jet is studied under various factors related to the diaphragm and the cavity geometry. Four diaphragms, manufactured from piezoelectric composites, were selected for this study, Bimorph, Thunder®, Lipca and RFD. The overall factors considered are the driving signals, voltage, frequency, cavity height, orifice size, and passive cavity pressure. Using the average maximum jet velocity as the response variable, these factors are individually studied for each actuator and statistical analysis tools were used to select the relevant factors in the response variable. For all diaphragms, the driving signal was found to be the most important factor, with the sawtooth signal producing significantly higher velocities than the sine signal. Cavity dimensions also proved to be relevant factors when considering the designing of a synthetic jet actuator. The cavities with the smaller orifice produced lower velocities than those with larger orifices and the cavities with smaller volumes followed the same trend. Although there exist a relationship between cavity height and orifice size, the orifice size appears as the dominant factor.Driving frequency of the diaphragm was the only common factor to all diaphragms studied that was not statistically significant having a small effect on jet velocity. However along with waveform, it had a combined effect on jet velocity for all actuators. With the sawtooth signal, the velocity remained constant after a particular low frequency, thus indicating that the synthetic jet cavity could be saturated and the flow choked. No such saturation point was reached with the sine signal, for the frequencies tested. Passive cavity pressure seemed to have a positive effect on the jet velocity up to a particular pressure characteristic of the diaphragm, beyond which the pressure had an adverse effect. For Thunder® and Lipca, the passive cavity pressure that produced a peak was measured at approximately 20 and 18kPa respectively independent of the waveform utilized. For a Bimorph and RFD, this effect was not observed.Linear models for all actuators with the factors found to be statistically significant were developed. These models should lead to further design improvements of synthetic jets.

Bombas de fluxo são dispositivos importantes em áreas como a Bioengenharia, Medicina, Farmácia, entre outras aplicações clássicas de Engenharia. Princípios para o bombeamento de fluidos baseados em atuadores piezelétricos estão sendo estudados no Departamento de Engenharia Mecatrônica e de Sistemas Mecânicos da Escola Politécnica, que permitem a construção de bombas de fluxo de pequena escala, ou seja, bombas de fluxo de pequena potência para deslocamento de pequenos volumes de fluido com baixo consumo de energia. O presente trabalho estuda bombas de fluxo piezelétricas de diafragma do tipo valve-less para geração de vazão. A bomba de fluxo piezelétrica de diafragma utiliza cerâmica piezelétrica como atuador para mover uma membrana (diafragma) para cima e para baixo como um pistão, que causa uma seqüência de aumento e diminuição do volume da câmara da bomba, forçando a entrada e a saída do fluido na bomba. A direção do fluxo é garantida por válvulas que privilegiam o fluxo em apenas um sentido. O objetivo deste trabalho é o estudo da metodologia de desenvolvimento de uma bomba de fluxo piezelétrica de diafragma de baixo custo do tipo valve-less. Para tanto, será utilizado a modelagem por Método dos Elementos Finitos (MEF) para a realização de análises de sensibilidade dos parâmetros geométricos e construtivos da bomba de fluxo. Serão realizadas simulações de escoamento de fluido pelo Método de Volumes Finitos (MVF) para a realização de análises de sensibilidade dos parâmetros geométricos dos elementos difusor/bocal e o levantamento das curvas características da bomba de fluxo. Por fim, protótipos serão construídos e caracterizados para validação dos resultados computacionais. Serão apresentadas a metodologia empregada e a discussão dos resultados obtidos, de forma a analisar o princípio proposto e os fenômenos físicos em questão. / Flow pumps act as important devices in areas as Bioengineering, Medicine, Pharmacy, among other areas of Engineering. Principles for pumping fluids based on piezoelectric actuators have been studied in the Department of Mechatronic and Mechanical Engineering of Escola Politécnica da Universidade de São Paulo, that allow the construction of small flow pumps, in other words, pumps for displacement of small fluid volumes with low power consumption. The present work studies valveless piezoelectric diaphragm flow pumps for flow generation. The piezoelectric diaphragm flow pump uses a piezoelectric ceramic as actuator to move a membrane (diaphragm) up and down as a piston. Consequently, there is a sequence of increase and decrease in the chamber volume that will force the fluid in and out of the pump. The direction of the flow is guaranteed by valves that privilege the flow in just one pumping direction. The main objective of this work is the study of a methodology to develop a low cost valve-less piezoelectric diaphragm flow pump. A sensitivity analysis is carried using computational simulation through the Finite Element Method (FEM) to study how construction parameters and assembly affect diaphragm flow pump performance. Using CFD simulations through the Finite Volume Method (FVM), a sensitivity analysis is done around nozzle/diffuser element geometrical parameters and pump characteristic curves are obtained. Finally, computational results are validated by prototype construction and characterization. The text presents methodologies employed and discusses the obtained results, analyzing the principle and the related physical phenomena.

Atuadores piezelétricos são dispositivos que permitem a conversão de energia elétrica em energia mecânica. Dentre os atuadores piezelétricos, destacam-se os bilaminares, que consistem em duas piezocerâmicas de polarização oposta (ou excitadas com cargas de sinal contrário) com um substrato entre elas. Os atuadores piezelétricos também podem ser miniaturizados, alcançando a escala de MEMS (Micro-Electric-Mechanical System). Este trabalho tem por objetivo desenvolver uma metodologia utilizando o Método de Otimização Topológica (MOT) para o projeto de atuadores piezelétricos com múltiplos graus de liberdade baseados no princípio bilaminar. A fase de projeto consiste na utilização do MOT para a determinação de uma configuração de atuadores que maximizem o deslocamento numa direção e sentido especificados para uma restrição na quantidade de material utilizado em cada camada, considerando a polarização da cerâmica piezelétrica presente nessa configuração e o acoplamento e simetria entre as camadas. Para a simulação do atuador é utilizado o Método dos Elementos Finitos (MEF) através de um elemento de placa piezelétrica isoparamétrico de oito nós expandido. O MOT, neste trabalho, utiliza o modelo de material denominado PEMAP-P (Material Piezelétrico com Penalização e Polarização). A técnica de projeção é utilizada junto ao MOT para a obtenção de um resultado com uma geometria bem definida. O problema de otimização é resolvido através de Programação Matemática Sequencial (PMS) através do algoritmo GCMMA (Globally Convergent Method of Moving Asymptotes). Como exemplo é estudado o projeto de um atuador piezelétrico para microespelhos. Dentre as configurações obtidas pelo MOT, uma é fabricada utilizando as técnicas de corte a laser e colagem e, posteriormente, é caracterizada. Finalmente, é realizada a comparação entre os resultados de simulação e experimentais do protótipo. / Piezoelectric actuators are devices that allow the conversion of electric energy to mechanical energy. Among the piezoelectric, the bimorph stands. It consists of two piezoceramic plates with opposite polarization (or excited with opposite sign charges) with a substrate between them. The piezoelectric actuators can also be miniaturized in a MEMS scale. This work aims the design of a methodology using the Topology Optimization Method (TOM) for the design of piezoelectric actuators with multiple degrees of freedom using the bimorph principle. The design phase applies the TOM to determine an optimized configuration of actuators that maximizes the output displacement in a specified direction and orientation for a constraint in the amount of material used at each layer, by considering the polarization of the piezoelectric ceramic present on this configuration and the coupling and symmetry between layers. The Finite Element Method (FEM) is applied for actuator simulation through an extended piezoelectric plate isoparametric element with 8 nodes. The TOM in this work employs a material model called PEMAP-P (Piezoelectric Material with Penalization and Polarization). The projection technique is implemented with TOM to obtain a result with a well-defined geometry. The optimization problem is solved by using Sequential Mathematical Programming (SMP) through the GCMMA algorithm (Globally Convergent Method of Moving Asymptotes). As an example, the design of a piezoelectric actuator for micromirrors is studied. Among the configurations obtained by the TOM, one is manufactured using laser cutting and bonding techniques and it is tested. Finally, a comparison between the simulated and experimental results from prototype is performed.