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Measurement of Parameters of Piezoelectric Active Elements for Acoustic Emission Sensors
Fialka, Jiří ; Erhart,, Jiří (referee) ; Sedlák, Petr (referee) ; Beneš, Petr (advisor)
The doctoral thesis discusses the measurement of parameters of piezoelectric (PZT) materials and the influence of temperature on their stability. In the introductory sections, the author briefly explains the piezoelectric effect and its use; simultaneously, methods for the preparation of piezoelectric materials and the measurement of their properties are presented to illustrate the analyzed problem. The experimental part of the thesis describes the procedure of measuring and calculating the complete matrix of material coefficients from samples of PZT ceramics. The applied set of piezoelectric samples complying with relevant European and world standards was made in the form of thin plates, thin discs and cylinders, via gradual modification of the large disc. The NCE51 and/or the older PCM51 ceramics obtained from the company Noliac Ceramics were used in determining the complete matrix and describing the measurement method. Both these types are soft piezoceramics composed from a solid solution of lead zirconate and lead titanate with the general chemical formula of Pb(Zr1-x,Tix)O3. The real crystallographic structure and chemical composition of the samples were confirmed by X-ray diffraction spectroscopy and energy dispersive spectroscopy (EDS), respectively. The frequency method was used for the measurement and calculation of all material coefficients. An Agilent 4294A impedance analyzer and a set of measuring tweezers marketed as “Tweezers Contact Test Fixture 16334A” were used in the process. Fast determination of the entire matrix of coefficients without any special requirement for the preparation of the samples to be measured was tested and verified. The charge coefficients of the piezoelectric material were confirmed by direct methods including the laser interferometer technique, the vibrometric method, and the procedure utilizing changes of the force applied to the sample. The advantages and disadvantages of the methods were compared and defined based on measurements and their results. The main part of thesis was focused on the behavior of piezoelectric material at high temperatures near the Curie point. Depolarization performed by means of a high temperature approaching the Curie point constitutes a significant yet hardly measurable material property of PZT ceramics. Commonly available vibrometric methods (d33-meters) do not appear to be suitable for the measurement of temperature dependencies, and for that reason the frequency technique was used. The piezoelectric charge coefficient, whose value can be effectively measured via the above-discussed frequency method, was selected as the indicator showing the depolarization state in the applied piezoelectric ceramics. The accuracy of the procedure was verified via comparison of the vibrometric method in cylinders of the NCE51 ceramics with different sizes, which are designed for the longitudinal length mode. The result is an optimized measurement methodology which facilitates accurate determination of the Curie temperature, namely phase transition to the cubic crystallographic structure. The experiment also proved the applicability of progressive, controlled depolarization of PZT ceramics via high temperature, and it also enabled us to define the temperature limits at which there occur irreversible changes of the piezoelectric properties of piezoceramics. In the measured NCE51 and PCM51 materials, the limit for the irreversible changes was equal to 95% of the Curie temperature.
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Modelling and Verification of Piezoelectric Generator
Lán, Radek ; Singule, Vladislav (referee) ; Hadaš, Zdeněk (advisor)
This master's thesis deals with the development and verification of the model of the piezoelectric generator, incl. determination of its parameters. This mathematical model should be used as a tool for development of new devices, especially for analysis of applicability of available energy source (vibration) and for design of device itself. At first the review of energy harvesting is described deeply. Subsequently piezoelectric generators and the ways how we can model them, are depicted in details. The methodology of parameters estimation and model development is presented in state space or in MATLAB/Simulink environment and applied on the commercial generator Midé V21BL. A device has been made within the scope of the thesis, which can be used as an universal tool in experiments with generator. Finally the model is applied on the analysis of energy yield from man's walk and there is also brief introduction to model modifications.
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Proposal of Microactuator Based on SMART Material
Hradil, Aleš ; Houška, Pavel (referee) ; Hadaš, Zdeněk (advisor)
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.
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Piezomotor control
Robotka, Jan ; Richter, Miloslav (referee) ; Macho, Tomáš (advisor)
This thesis aims to propose and implement a control system for a new type of piezomotor with the action elements of MPA for the purpose of measuring characteristics of this piezomotor needed for its use in practice. At the beginning the text processes theoretical data needed for design the control system. The author describes the principle of piezoelectric effect and deals with issues of piezomotors, which are based on this principle. Primarily theoretical knowledge relating to the piezomotor is processed. He also describes the characteristic of microcontroller C8051F015 based on processor core 8051, which is main element of whole control system. His peripherals, which are used in control system, are described more. One of the main parts of the text is design of analog board, which create sawmill course of voltage on piezocrystals of piezomotor. Images are used for description its individual parts. The circuit is controlled by digital and analog outputs of the microcontroller. Another part of the work is focused on communication between microcontroller and PC, which transmits instructions from user using the serial line. Further options of proposed application are shown and important used software components are described. Equally important is program for the microcontroller, which processes incoming messages from PC and manages its digital and analog outputs. In the next chapter is shown design of piezomotor and implementation of prototype the control system. Conclusion of work is devoted to measurement of piezomotor characteristics that shows resolution dependence on frequency, voltage amplitude and vertical pressure. The outgrowth of project, which is elaborated in this work, is the functional control system for the piezomotor with possibility of control through user application on PC. Obtained characteristics of piezomotor will be used for implementation into practice.
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PiezoLegs motor in medical aplication
Plass, Petr ; Koláčný, Josef (referee) ; Ondrák, Tomáš (advisor)
The Bachelor’s thesis is focused to explain of basic conceptions of piezoelectric motors including principles of piezoelectric effect. It is analysed velocities of movement of PiezoWave motor during loading and he is valued supply voltage of used demo driver. Then it is considered of drive with stepper motor and DC motor, it is compared them with piezoelectric motor and chosen the best alternate for the drive of a pump of the artificial heart. Then it is introduced with working in a program i-Speed 2 to analyzing of shots catch by the high speed video camera and it is given a basic manual to connecting, setting and programming of the drive connected to the EPOS P driving unit.
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Microposition control device
Kokeš, Ondřej ; Bajer, Arnošt (referee) ; Kadlec, Jaroslav (advisor)
Presented thesis analyses a function of the particular type of the nanopositioner with aim to suggest and construct an electronic device suitable for control of the nanopositioner slider. In presented material there is a description of the control signals and possibility of their generating in the respect of slider movement accuracy. The main goal of the thesis is to describe electronic units ranging from power supply, control processor unit part to end part that directly joint nanopositioner. There is also programme equipment for microcontroller and computer, communication description, movement measuring and calibration and draft for the close-up of the control loop for additional increase of the movement accuracy.
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Surface acoustic wave filter
Tichý, Jakub ; Dědková, Jarmila (referee) ; Raida, Zbyněk (advisor)
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.
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Study of Electromechanical Power Generator for Energy Harvesting Use
Adámek, Pavel ; Singule, Vladislav (referee) ; Hadaš, Zdeněk (advisor)
This work deals with complex information about state-of-the-art harvesting electric energy from mechanical energy. Particular constructional and physical principles of electromechanical conversion are shown. Further, it presents a proposal of generator, which the owner would be able to carry always without being troubled by it (e.g. generator electric energy in shoe) and which would feed energetically simple devices.
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