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Electrical characterization of flexible nanofiber piezoelectric materials
Pokorná, Romana ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This bacherol thesis is focused on piezoelectric nanofibrous materials. The first part describes the formation, use and possible aplications of nanofibers. It further analyze the principle of piezoelectric effect. It is a conversion of mechanical energy into electric energy and conversely. The second part is focused on design of experimental workplace for measurement of functional material properties. The last section of the thesis is dedicated to the electrical characterization of PVDF nanofibers and to the measurement of the piezoelectric charge constant.
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Nonlinear Energy Harvesting Devices
Rubeš, Ondřej ; Singule, Vladislav (referee) ; Maga, Dušan (referee) ; Hadaš, Zdeněk (advisor)
This thesis is focused on vibration energy harvester, which is a device converting kinetic energy of vibrations into electrical energy. The approximate dimensions of the device are ten centimeters, and the output power is in milliwatts. A device that generates such amount of power can function as a power source for communication modules and can be used for wireless sensors, which can be utilized for example in the Internet of Things. Existing devices are based on a simple linear oscillator, but they have a narrow operating frequency bandwidth, where they can operate effectively. The bandwidth extension of vibration energy harvesters using nonlinear characteristics is the main aim of this thesis. It leads to a design of a nonlinear device with wide operating frequency bandwidth that provides higher implementation in industry.
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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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Measurement of energy harvesters
Kašpárek, Ondřej ; Pikula, Stanislav (referee) ; Kunz, Jan (advisor)
Over recent years the power outputs of piezoelectric energy harvesters have increased to the point where they rival other types of energy harvesting and therefore their sufficient parameterization is necessary. Four piezoelectric PVDF films - DT1-028KL, DT1-052K, DT2-028K a LDT2-028K made by SENZOR SOLUTIONS TE Connectivity were parametrized by two created systems of measurement with force strain. Power outputs of these films when pressed with harmonic force signal with 3 Nrms amplitude are in nW and transferred energies after force impulse with size 300 N are between hundreds and tenths of fJ. Furthermore, values of quality factor, resonance frequency, optimal load resistance and maximal power stability were determined.
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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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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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Piezoelectricity in technical practice
Škarabelová, Lenka ; Frk, Martin (referee) ; Kazelle, Jiří (advisor)
Bachelor's thesis is dedicated to the study of the principle and possibilities of use of the piezoelectric effect. Since the use of piezoelectric effect in electrical engineering is very extensive, the main focus is placed on the ability to exploit this effect in the field of ultrasonic and piezoelectric resonators. Next aim of this work is practically and theoretically to get acquainted with the measurement of small changes in weight, using electrochemical quartz crystal microbalance (EQCM), also with an ultrasonic equipment from company Olympus and ultrasonic defectoscopy for detection of possible imperfections in the material and their evaluation.
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Fabrication of ceramic materials for piezoelectric applications
Karkuszová, Karina ; Spusta, Tomáš (referee) ; Částková, Klára (advisor)
The content of this thesis is about preparation and processing of lead-free piezoceramic materials with perovskite structure. Potassium sodium niobate (KNN) powder was prepared by solid state reaction (SSR) and liquid phase reaction (sol-gel reaction). The powders were formed by uniaxial and isostatic pressing and further sintered. The density, grain size and morphology were determined on the sintered samples. The powder, synthesised by SSR and sintered in a conventional furnace, was chosen as a standard. The maximum density achieved on samples after optimization of sintering cycle was 93 %TD. The sintering optimization involved a homogenization step at 950 °C, which promotes the correct development of the phase composition and microstructure, followed by sintering at 1120 °C. The same approach and sintering cycle were used for sintering the samples, prepared by sol-gel synthesis. The maximum density of the samples prepared by sol-gel reaction and sintered in a conventional way, was 92 %TD. For further comparison, both of the synthesised powders were sintered using SPS (spark plasma sintering), which increased their final density up to 97 %TD. The approximate value of the piezoelectric coefficient d33 (pC/N) has been measured on selected SSR samples with pure phase composition ((K0,5Na0,5)NbO3). The best measured value of d33 was around 100 pC/N.
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Piezoelectric vibration energy harvester
Klásek, Matyáš ; Rubeš, Ondřej (referee) ; Hadaš, Zdeněk (advisor)
The first goal of this bachelor’s thesis is to give an overview of piezoelectric materials and their utilization in energy harvesting applications. The second goal is to examine the effect of altering model parameters on generated power and natural frequency of the system using analytical model of a bimorph piezoelectric cantilever beam in MATLAB/Simulink.
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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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