National Repository of Grey Literature 127 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Monitoring of dynamic systems with piezoelectric sensors
Svoboda, Lukáš ; Hadaš, Zdeněk (referee) ; Kšica, Filip (advisor)
The aim of this diploma thesis is to describe localization and calculation load identification of dynamic systems using piezoelectric sensors. Finding methods, which would allow us to evaluate loads on simple systems is the key to their application in the structural health monitoring of more complex systems. A theory necessary for understanding and application in aerospace, civil engineering, automobile industry, and train traffic of presented methods is given in the first part of the thesis. In these applications, the methods of wave propagation and different types of neural network methods are used to evaluate load identification. It is possible to evaluate loads by using a time reverse method, a method based on signal deconvolution, and a method based on a voltage amplitude ratio of the piezoelectric sensor. In the next part, the methods are described, the suitable place for gluing of a sensor, and the number of sensors for using method is given. These methods were verified and compared to a simple experimental system. In the following part, the model of the piezoelectric sensor is presented. It is possible to use the model for calculating voltage output from the strain. For methods verification, the problem of train passage in a specific place of the railway is chosen. The speed of the train and its load on the railway was calculated by using these methods.
Dynamika soustav těles s neurčitostním modelem vzájemné vazby
Svobodová, Miriam ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deal with evaluation of the impact in the scale of uncertaintly stiffness on the tool deviation during grooving process. By the affect of the insufficient stiffness in each parts of the machine, there is presented a mechanical vibration during the cutting process which may cause a damage to the surface of the workpiece, to the tool or to the processing machine. The change of the stiffness is caused in the result of tool wear, impact of setted cutting conditions and many others. In the first part includes teoretical introduction to field of the uncertainty and choosing suitable methods for the solutions. Chosen methods are Monte Carlo and polynomial chaos expansion which are procced in the interface of MATLAB. Both of the methods are primery tested on the simple systems with the indefinited enters of the stiffness. These systems replace the parts of the stiffness characteristics of the each support parts. After that, the model is defined for the turning during the process of grooving with the 3 degrees of freedom. Then the analyses of the uncertainity and also sensibility analyses for uncertainity entering data of the stiffness are carried out again by both methods. At the end are both methods compared in the points of view by the time consuption and also by precission. Judging by gathered data it is clear that the change of the stiffness has significant impact on vibration in all degrees of freedome of the analysed model. As the example a maximum and a minimum calculated deviation of the workpiece stiffness was calculated via methode of Monte Carlo. The biggest impact on the finall vibration of the tool is found by stiffness of the ball screw. The solution was developed for the more stabile cutting process.
Verification of operation of piezoelectric composite strain sensor
Kubiš, Juraj ; Ševeček, Oldřich (referee) ; Hadaš, Zdeněk (advisor)
The bachelor thesis deals with the use of piezoelectric elements as sensing elements in engineering practice. The work can be divided into three main parts. The first part describes the actual use of these elements in practice, either as sensing elements or as a source for energy harvesting. This section contains the selection of components for a given experiment, the creation of a model using FEM and the measurement process of the experiment. The third part is the evaluation of the obtained results and subsequent comparison with the obtained values from strain gauges and other sensors.
Analysis of model operation of multi-degree-of-freedom energy harvester
Witassek, Tomáš ; Rubeš, Ondřej (referee) ; Hadaš, Zdeněk (advisor)
The first part of this bachelor’s thesis is an overview of vibration energy harversters with multiple degrees of freedom. Several options of broadening the usefull frequency bandwidth thanks to multiple degrees of freedom are described in the overview. The following part is a model in Matlab & Simulink analyzing behaviour of a vibration-powered generator with a harmonic excitation and another one with a real excitation. The main focus is on the output electrical power and energy in relation to geometrical parameters and electromagnetic damping.
Design of vibration energy harvester with blade joint
Beňo, Martin ; Hadaš, Zdeněk (referee) ; Rubeš, Ondřej (advisor)
This bachelor thesis deals with the design of vibration generator with blade joint. Firstly, its main aim is to design a working vibration generator, and secondly is to entice the reader to continue on with reading. Such a vibration generator is a handy, inexpensive to manufacture, and especially very simple. The basic design element of the vibration generator is oscillating frame connected to the blade joint and is the carrier of the magnets. The electrical part of the generator consists of a magnetic circuit and coil on the static bracket. Oscillating frame with magnet creates a changing magnetic field and induces voltage in the coil. For the design of the construction was used the program Inventor. For the calculation of the magnetic circuit has been selected, the program FEMM controlled by MATLAB. For the calculation of the static and the dynamic analysis was chosen the program ANSYS.
Design of electronic subsystem for reduced gravity impact simulator
Ostrý, Lubomír ; Hadaš, Zdeněk (referee) ; Věchet, Stanislav (advisor)
The focus of this thesis is development of an electronic subsystem for reduced gravity impact simulator. The research part of this thesis firstly covers methods used for simulation of microgravity or reduced gravity and compares them. Another part of research focuses on three selected potential approaches to creating the electronic subsystem for this device. The second, practical, part of this thesis describes the design and development of the electronic subsystem. The foundation of the electronic subsystem is a control unit which has been developed on the basis of an STMicroelectronics microcontroller. Using the control unit, the electronic subsystem measures pressure, position, acceleration and force in the system. Another task of the control unit is control of a stepper motor. Integration of individual elements into the electronic subsystem is described both in terms of software and hardware. Furthermore, a graphic user interface program for PC has been developed as a means to interact with the system. In the final part of the thesis, the operation of the electronic subsystem is described and lastly, the electronic subsystem is evaluated.
Design of tester of piezoelectric PVDF layers
Sijková, Simona ; Rubeš, Ondřej (referee) ; Hadaš, Zdeněk (advisor)
The diploma thesis deals with a design of a tester device, a selection and verification of a suitable method for comparing the piezoelectric properties of tested PVDF samples. In the introduction, a basic overview of the theory is important to understand the issue and the various branches of use of PVDF in the field of energy harvesting. The tester device includes a unimorph piezoelectric cantilever beam with tip mass, whose properties are described by three models: a model with N degrees of freedom reduced to one degree of freedom (NDOF), a single degree of freedom model (SDOF), both created in Matlab and a model for verifying results in FEM ANSYS Workbench program. The voltage time response and the voltage frequency response of the models is compared with each other. For two different PVDF samples, the voltage response to harmonic excitation is measured using a tester device, and the piezoelectric properties of one of them are determined using the NDOF and SDOF models.
Development of PVDF nanofibers sensor
Klásek, Matyáš ; Tofel, Pavel (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deals with the feasibility of using PVDF nanofibers as an active sensor layer generating electrical signal. PVDF and related electromechanical effects are described. A research study is conducted regarding existing PVDF nanofiber applications and based on it, an event sensor design utilizing triboelectric effect and electrostatic induction is proposed. The electrical response of the layers is experimentally investigated and a pulse detection algorithm is conceived and implemented. Finally, a way of integrating the sensor into a rail track is proposed.
Analysis of SMART Material Usage in case of Active Vibration Sensing
Rabčan, Jakub ; Věchet, Stanislav (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deals with the possibility of vibration sensing and vibrodiagnostics based on the use of so-called "SMART" materials such as piezoelectric layers or structures. Research studies have examined the general overview of vibrodiagnostic methods and their analysis of the possibility of sensing vibration by piezoelectric structures. This was followed by measuring and evaluating the results using various vibro-diagnostic methods. The results were compared with those obtained by sensing vibration using an accelerometer. We also dealt with the problem of detecting the deformation of the device by sensing vibration with piezoelectric structures. The last part was programming the "Myrio" to capture and evaluate the vibration using Labview.
Analysis of walking as energy source for biomedical applications
Cieslar, Filip ; Kovář, Jiří (referee) ; Hadaš, Zdeněk (advisor)
This paper deals with measurements and statistical processing of the acceleration data measured in the area of the human head. Types, principles of biomedical applications are shown, and problems pointed to its power supply. There are efforts to earn energy from surroundings of devices and extend its lifespan. Kinetic energy harvesters require such levels of acceleration for their excitation, that could possibly be obtained from human movements. 30 different people with different characteristics were thus measured during walking in order to find the common frequencies and relevant magnitudes created through vibrations during walking. Energy efficiency is evaluated using generator and use of this source to supply biomedical devices.

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