Wyniki wyszukiwania - Biblioteka Nauki

1

Acoustical Analysis of Enclosure as Initial Approach to Vehicle Induced Noise Analysis Comparatevely Using STFT and Wavelets

100%

Błażejewski A. , Kozioł P. , Łuczak M.

|

2014

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tom Vol. 39, No. 3

385--394

EN

It is assumed in the paper that the signals in the enclosure in a transient period are similar to a noise induced by vehicles, tracks, cars, etc. passing by. The components of such signals usually points out specific dynamic processes running during the observation or measurements. In order to choose the best method of analysis of these phenomena, an acoustic field in a closed space with a sound source inside is created. Acoustic modes of this space influence the sound field. Analytically, the modal analyses describe the above mentioned phenomena. The experimental measurements were conducted in the room that might comprise the closed space with known boundary conditions and the sound source Br¨uel & Kjær Omni-directional type 4292 inside. To record sound signals before the field’s steady state was reached, the microphone type 4349 and the 4-channel frontend 3590 had been used. The obtained signals have been analysed by using two approaches, i.e. Fourier and the wavelet analysis, with the emphasis on their efficiency and the capability to recognise important details of the signal. The results obtained for the enclosure might lead to the formulation of a methodology for an extended investigation of a rail track or vehicles dynamics.

2

Stator Winding Fault Detection of Permanent Magnet Synchronous Motors Based on the Short-Time Fourier Transform

88%

Pietrzak P. , Wolkiewicz M.

Power Electronics and Drives

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2022

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tom Vol. 7 (42)

112--133

EN

In modern drive systems, the high-efficient permanent magnet synchronous motors (PMSMs) have become one of the most substantial components. Nevertheless, such machines are exposed to various types of faults. Hence, on-line condition monitoring and fault diagnosis of PMSMs have become necessary. One of the most common PMSM faults is the stator winding fault. Due to the destructive character of this failure, it is necessary to use fault diagnostic methods that allow fault detection at its early stage. The article presents the results of experimental studies obtained from fast Fourier transform (FFT) and short-time Fourier transform (STFT) analyses of the stator phase current, stator phase current envelope and stator phase current space vector module. The superiority of the proposed method over the classical approach based on the stator current analysis using FFT is highlighted. The proposed solution is experimentally verified under various motor operating conditions. The application of STFT analysis discussed so far in the literature has been limited to the fault diagnosis of induction motors and the narrow range of the analysed motor operating conditions. Moreover, there are no works in the field of motor diagnostics dealing with STFT analysis for stator windings based on the stator current envelope and the stator current space vector module.

3

Comparison of multiband filtering, empirical mode decomposition and short-time fourier transform used to extract physiological components from long-term heart rate variability

75%

Adamczyk K. , Polak A. G.

Metrology and Measurement Systems

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2021

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tom Vol. 28, nr 4

643--660

EN

Heart rate is constantly changing under the influence of many control signals, as manifested by heart rate variability (HRV). HRV is a nonstationary, irregularly sampled signal, the spectrum of which reveals distinct bands of high, low, very low and ultra-low frequencies (HF, LF, VLF, ULF). VLF and ULF components are the least understood, and their analysis requires HRV records lasting many hours. Moreover, there are still no well-established methods for the reliable extraction of these components. The aim of this work was to select, implement and compare methods which can solve this problem. The performance of multiband filtering (MBF), empirical mode decomposition and the short-time Fourier transform was tested, using synthetic HRV as the ground truth for methods evaluation as well as real data of three patients selected from 25 polysomnographic records with a clear HF component in their spectrograms. The study provided new insights into the components of long-term HRV, including the character of its amplitude and frequency modulation obtained with the Hilbert transform. In addition, the reliability of the extracted HF, LF, VLF and ULF waveforms was demonstrated, and MBF turned out to be the most accurate method, though the signal is strongly nonstationary. The possibility of isolating such waveforms is of great importance both in physiology and pathophysiology, as well as in the automation of medical diagnostics based on HRV.

4

Analysis of vibration transmission in an air-operated demolition hammer

75%

Tabaszewski M. , Wojsznis M.

Vibrations in Physical Systems

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2016

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tom Vol. 27

385--390

EN

The paper presents an analysis of vibrations of a ram, body and handle of a heavy, air-operated demolition hammer. The research was conducted in order to determine the character of dynamic inputs and resulting vibrations at the tool handle which were necessary to build a structural model of local influences on an operator taking the hammer design into account. The experiment was carried out on a test stand without participation of an operator, which guaranteed repeatability of measurements and elimination of ontogenetic characteristics. The displacements of selected structural elements of the tool were recorded by means of a camera and the accelerations at the handle were recorded by means of a standard measuring apparatus. The recorded signals were subjected to the spectral analysis and the short-time Fourier transform (STFT) using dedicated software in MATLAB environment.

5

Krótkoczasowa transformata Fouriera impulsów ultraszerokopasmowych UWB

75%

Garbaruk M. , Litwińczuk N.

Przegląd Elektrotechniczny

|

2015

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tom R. 91, nr 1

95-98

PL

W artykule przedstawione zostało zastosowanie krótkoczasowej transformaty Fouriera (STFT) do analizy ultraszerokopasmowych impulsów falkowych. Pokazano wybrane okna czasowe wykorzystywane w analizie STFT oraz ich wpływ na wyznaczone spektrogramy Fouriera impulsów UWB. Spektrogramy Fouriera pokazane zostały w formie poziomicowej oraz jako rysunki trójwymiarowe 3D.

EN

A short-time Fourier transform (STFT) applied to ultrawideband wavelet pulses was presented in the paper. Different window functions of STFT were shown and used to calculate Fourier spectrograms of wavelet UWB pulses. Fourier spectrograms were presented as 2D and 3D figures.

6

Comparison of multiband filtering, empirical mode decomposition and short-time fourier transform used to extract physiological components from long-term heart rate variability

75%

Adamczyk K. , Polak A. G. , Adamczyk K. , Polak A. G.

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nr 4

7

Short-time Fourier transform of ultrawideband signals

75%

Garbaruk M. , Litwińczuk N.

Przegląd Elektrotechniczny

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2016

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tom R. 92, nr 2

26--28

EN

The paper presents theoretical bases concerning the usage of a short-time Fourier transform for the analysis of UWB pulses. In the article there was shown the analysis of Fourier spectrograms of a base UWB wavelet interfered with other signals of different forms: UWB wavelets, an UWB Gaussian pulse and a continuous sine signal. 2D and 3D spectrograms of signals were calculated and compared to the results obtained using a normal Fourier transform.

PL

W artykule omówiono wykorzystanie krótkoczasowej transformaty Fouriera do analizy sygnałów ultraszerokopasmowych UWB. Jako przykład rozpatrzono impuls falkowy UWB zakłócony innymi sygnałami o różnych formach: impulsami UWB oraz ciągłym sygnałem sinusoidalnym. Przedstawiono porównanie wyników analizy sygnałów uzyskanych za pomocą transformaty STFT i klasycznego przekształcenia Fouriera.

8

A continuous wavelet transform treatment of surface electromyographic (EMG) signals obtained from patients with low back pain before and after rehabilitation

75%

Panagiotacopulos N. , Amos M. , Panayotakopoulos D.

Image Processing & Communications

|

2002

|

tom Vol. 8, no 2

113-120

EN

In this article we present the results of a study based on continuous wavelet transforms (CWT) of surface EMG signals. This analysis provides the distribution of the energy of the signal in the time-scale plane (scalogram). The data used in this study were signals obtained from patients with low back problems, and the analysis showed that there exist visual differences between the muscle responses before and after rehabilitation, as it can be seen in the associated scalograms.

9

Analysis of the flame pulsation signals using a short-time Fourier transform

75%

Grądz Ż.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

|

2018

|

tom T. 8, nr 3

51--54

EN

The main aim of the diagnostics of combustion process is ensuring its stability and efficiency. The most important aspect related to the monitoring of the combustion process is a non-invasive acquisition of information from flame and subsequently subjecting it for further processing. Such method of research allows to evaluate the course of the process and determine the characteristic conditions under which the combustion process is stable or not. The article presents the application of short-time Fourier transform for the analysis of flame pulsation signals. The aim of the research was to find an area especially sensitive to the change of combustion process conditions.

PL

Głównym celem stawianym diagnostyce procesu spalania jest zapewnienie stabilności i efektywności przebiegu procesu. Najważniejszym aspektem monitorowania procesu spalania jest pozyskiwanie w sposób bezinwazyjny informacji z płomienia, a następnie poddanie jej dalszemu przetwarzaniu. Taki sposób badań pozwala na ocenę przebiegu procesu i daje możliwość wyznaczania charakterystycznych stanów, w których proces przebiega stabilnie lub nie. W artykule przedstawiono wykorzystanie krótkoczasowej transformaty Fouriera do analizy sygnałów pulsacji płomienia. Celem badań było znalezienie obszaru szczególnie wrażliwego na zmianę warunków w procesie spalania.

10

Zastosowanie krótkoczasowej transformaty Fouriera oraz sztucznej inteligencji do wykrywania uszkodzeń uzwojeń stojana silnika synchronicznego o magnesach trwałych

75%

Pietrzak P. , Wolkiewicz M.

Przegląd Elektrotechniczny

|

2023

|

tom R. 99, nr 4

22--29

PL

W artykule przedstawiono możliwość wykorzystania krótkoczasowej transformaty Fouriera sygnału prądu fazowego stojana oraz modułu wektora przestrzennego prądów stojana do ekstrakcji symptomów uszkodzeń uzwojeń stojana silnika synchronicznego o magnesach trwałych. Dodatkowo, zaproponowano możliwość automatyzacji procesu wnioskowania o stanie uzwojenia stojana przy zastosowaniu wybranych algorytmów bazujących na sztucznej inteligencji: maszyny wektorów nośnych oraz perceptronu wielowarstwowego. System diagnostyczny rozszerzono o możliwość lokalizacji uszkodzonej fazy. Badania eksperymentalna potwierdzają wysoką skuteczność opracowanego rozwiązania.

EN

This paper presents the possibility of using the short-time Fourier transform of the stator phase current and stator current space vector module in the process of permanent magnet synchronous motor stator winding fault symptoms extraction. Additionally, the automatization of the stator winding condition inference process which the use of selected artificial intelligence based algorithms: Support Vector Machine and MultiLayer Perceptron is proposed. The developed diagnostic system has been extended with the functionality of locating the damaged phase. Experimental studies confirmed the high effectiveness of the developed method.

11

Comparison of the EEG Signal Classifiers LDA, NBC and GNBC Based on Time-Frequency Features

63%

Szuflitowska B. , Orłowski P.

Pomiary Automatyka Robotyka

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2017

|

tom R. 21, nr 2

39--45

EN

EEG signals are non-stationary and used to study the activities of the brain in pathology. Epilepsy belongs to the most common neurological diseases. In the paper, real EEG sequences described by a doctor as normal and epileptic (ictal and interictal) are used. In classification process these sequences are divided into training and testing subsets. The classification are performed using Short-Time Fourier Transform. Based on obtained spectrum four features have been extracted. The study presents experiments based on the analysis and classification of EEG signals using various methods, including Linear Discriminant Analysis, Naive Bayes Classifier and Gaussian Naive Bayes Classifier. The results indicated that used techniques a potential to be applied within an automatic neurologic diseases diagnosis system and could thus further increase the number of correct diagnoses.

PL

Sygnały EEG są z definicji niestacjonarne i stosowane do badania aktywności mózgu w patologii. Epilepsja należy do najczęstszych chorób neurologicznych. W pracy użyto rzeczywistych sekwencji EEG określonych przez lekarza jako stan normalny oraz padaczka (stany napadowe oraz międzynapadowe). W procesie klasyfikacji sygnały zostały podzielone na dwa podzbiory – uczący oraz testujący. Klasyfikacja została przeprowadzona za pomocą krótkotrwałej transformaty Fouriera. Na podstawie otrzymanego widma dokonano ekstrakcji czterech cech. Badanie przedstawia eksperymenty oparte na analizie i klasyfikacji sygnałów EEG za pomocą różnych metod, w tym Liniowej Analizy Dyskryminacyjnej, Naiwnego Klasyfikatora Bayesa oraz Naiwnego Klasyfikatora Bayesa dla rozkładu Gaussa. Wyniki pokazują, że użyty algorytm może być potencjalnie stosowany w automatycznej diagnostyce schorzeń neurologicznych i może w przyszłości zwiększyć liczbę poprawnie stawianych diagnoz.

12

Wykorzystanie STFT w identyfikacji stanu technicznego amortyzatorów badanych metodą drgań swobodnych

63%

Gardulski J. , Konieczny Ł. , Burdzik R.

Zeszyty Naukowe. Transport / Politechnika Śląska

|

2005

|

tom z. 57

107-114

PL

W pracy przedstawiono wyniki analiz wibroakustycznych sygnałów drganiowych generowanych przez zawieszenie samochodu osobowego pobudzone do drgań wymuszeniem impulsowym. Do analizy sygnału wykorzystano krótkoczasową transformatę Fouriera (Short Time Fourier Transform) z zastosowaniem okna Hamminga z 75% nakładaniem się okien. Badania obejmowały amortyzatory z zaprogramowanymi usterkami w postaci ubytku uszczelnienia tłoczka oraz ubytku płynu amortyzatorowego, które zostały zabudowane w samochodzie marki Skoda Fabia.

EN

The paper presents the results of vibration signals analysis generate by car suspension stimulate to vibration impulse signal. Signal analysis used Short Time Fourier Transform with Hamming window superimpose to 75%. Research range shock absorber with programmed fault form as loss throng seal and as loss shock absorber fluid, built in Skoda Fabia passenger car.

13

Bearing estimation using double frequency reassignment for a linear passive array

63%

Czarnecki K. , Leśniak W.

Polish Maritime Research

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2017

|

tom nr 3

26--35

EN

The paper demonstrates the use of frequency reassignment for bearing estimation. For this task, signals derived from a linear equispaced passive array are used. The presented method makes use of Fourier transformation based spatial spectrum estimation. It is further developed through the application of two-dimensional reassignment, which leads to obtaining highly concentrated energy distributions in the joint frequency-angle domain and sharp graphical imaging. The introduced method can be used for analysing, a priori, unknown signals of broadband, nonstationary, and/or multicomponent type. For such signals, the direction of arrival is obtained based upon the marginal energy distribution in the angle domain, through searching for arguments of its maxima. In the paper, bearing estimation of three popular types of sonar pulses, including linear and hyperbolic frequency modulated pulses, as well as no frequency modulation at all, is considered. The results of numerical experiments performed in the presence of additive white Gaussian noise are presented and compared to conventional digital sum-delay beamforming performed in the time domain. The root-mean-square error and the peak-to-average power ratio, also known as the crest factor, are introduced in order to estimate, respectively, the accuracy of the methods and the sharpness of the obtained energy distributions in the angle domain.

14

Detection of Arrhythmia using Neural Network

63%

Mohapatra S. K. , Palo H. K. , Mohanty M. N.

Annals of Computer Science and Information Systems

|

2018

|

tom Vol. 14

97--100

EN

There is an increase in cardio logical patients all over the world due to change in modern life style. It forces the medical researchers to search for smart devices that can diagnosis and predict the onset of cardiac problem before it is too late. This motivates the authors to predict Arrhythmia that can help both the patients and the medical practitioners for better healthcare services. The proposed method uses the frequency domain information which can represent the ECG signals of Arrhythmia patients better. Features representing the MIT-BIH Arrhythmia are extracted using the efficient Short Time Fourier Transform and the Wavelet transform. A comparison of these features is made with that of normal human being using Neural Network based classifier. Wavelet based features has shown an improvement of Accuracy over that of STFT features in classifying Arrhythmia as our results reveal. A Mean Square Error (MSE) of with wavelet transform has validated our results.

15

The time and power spectrum density analysis of different lightning components based on electric field waveforms from 2014 thunderstorm season recorded in the south-eastern part of Poland

63%

Karnas G. , Barański P. , Masłowski G. , Sobolewski K.

Przegląd Elektrotechniczny

|

2016

|

tom R. 92, nr 2

144--147

EN

This paper is focused on the Power Spectrum Density analysis of the lightning electric field signatures collected in Subcarpathian part of Poland, in 2014. Lightning records were carried out in two different ways. The slow electric field sensor (TLF-ELF), the mill, was used for observation of lightning activity during entire thunderstorm lifetime. The second recording mode was the acquisition of fast electric field changes (0.3 Hz to 3 MHz) associated with different types of cloud-to-ground (CG) and inter-, intra-cloud (IC) type discharges. The registration process was synchronized with microsecond time precision. This allowed to relate lightning stroke detections to these reported by the LINET, the commercial lightning location system. Different lightning stroke components, as e.g. the preliminary breakdown (PB), the return stroke (RS) and the continuing current (CC) were identified with application of the Short-Time Fourier Transform. The spectral analysis might be adapted to improve in future some detection algorithms used in lightning location systems. Such lightning CG stroke discrimination is not applied as yet by any lightning location system routinely operated in Europe.

PL

W artykule skupiono się na analizie spektrogramów widmowej gęstości mocy wyznaczonych dla różnych przebiegów piorunowego pola elektrycznego zebranych w południowo-wschodniej części Polski w 2014 roku. Dane zostały zebrane z wykorzystaniem dwóch sensorów pola elektrycznego. Sensor pola elektrycznego pracujący w zakresie TLF-ELF umożliwił obserwację aktywności burzowej w długofalowym okresie czasu. Drugi typ rejestracji obejmował akwizycję szybkich zmian pola elektrycznego (0.3 Hz do 3 MHz) pochodzących of różnych typów wyładowań doziemnych oraz wewnątrz-, między-chmurowych. Proces rejestracji został zsynchronizowany z mikrosekundową precyzją. Pozwoliło to na porównanie własnych rejestracji z detekcjami LINET-u – komercyjnego systemu lokalizacji wyładowań. Różne składowe wyładowania takie jak wyładowania wstępne, udar główny oraz prąd długotrwały zostały zidentyfikowane z wykorzystaniem krótkoczasowej transformaty Fouriera. Analiza spektralna może w przyszłości zostać wykorzystana w usprawnieniu algorytmów detekcji wyładowań. Taki rodzaj identyfikacji wyładowań doziemnych nie został jak dotąd zaimplementowany w żadnym systemie lokalizacji wyładowań atmosferycznych pracującym regularnie w obszarze Europy.

16

Analiza spalania stukowego w silniku tłokowym za pomocą charakterystyk czasowo-częstotliwościowych

63%

Szwaja S.

Silniki Spalinowe

|

2009

|

tom R. 48, SC2

306--315

PL

W artykule zaprezentowano analityczną metodę opisu intensywności stuku za pomocą charakterystyk czasowo-częstotliwościowych składowej zmiennej ciśnienia spalania w cylindrze silnika tłokowego pracującego ze stałą prędkością obrotową i zasilanego wodorem lub benzyną. Składową zmienną ciśnienia spalania uzyskano w wyniku odfiltrowania jej z przebiegu ciśnienia w cylindrze za pomocą filtra górno-przepustowego o częstotliwości granicznej nieco mniejszej od częstotliwości pierwszej składowej harmonicznej (ok. 3,5kHz). Następnie, tak uzyskaną składową zmienną ciśnienia poddano okienkowej (krótko-czasowej) transformacji Fouriera (STFT), w wyniku, czego uzyskano zbiór charakterystyk widma amplitudowego dla kolejno po sobie następujących chwil czasu. Następnie, za pomocą tak skonstruowanych charakterystyk czasowo-częstotliwościowych dokonano porównania przebiegu spalania stukowego w silniku zasilanym wodorem i benzyną.

EN

An analytical method based on time-frequency representations for examining combustion knock in an internal combustion engine is described in this paper. Combustion knock was examined by high frequency component of an in-cylinder pressure acquisitied during combustion of hydrogen and gasoline in the CFR engine working at constant rotational speed. The high frequency component of the in-cylinder pressure was obtained by filtering the in-cylinder pressure using for this purpose the digital high-pass Butterworth filter with cut-off frequency of 3.5kHz, which was a bit lower than the basic frequency mode of the high frequency pressure component. Next, this high frequency component of the in-cylinder pressure was used as input data for the short time Fourier transform. As result of computing set of frequency responses were determined. Further, timefrequency representation (TFR) was built on this set of frequency responses. Finally, comparisons between TFRs for hydrogen and gasoline combustion knock were done.

17

Zastosowanie krótkoczasowej transformaty Fouriera w diagnostyce zawieszeń pojazdów samochodowych

63%

Gardulski J. , Warczek J.

Zeszyty Naukowe. Transport / Politechnika Śląska

|

2002

|

tom z. 44

23-29

PL

W artykule przedstawiono metodę diagnozowania stanu technicznego elementów zawieszeń samochodowych opartą na krótkoczasowej transformacie Fouriera. Obiekt badawczy to samochód osobowy, w którego przednim zawieszeniu wprowadzono usterki. Wyniki analiz w postaci widm czasowo-częstotliwościowych wykazują czułość zastosowanej metody w zakresie wykrywania wprowadzonych do układu zawieszenia uszkodzeń.

EN

The paper presents diagnostics method of technical state part of car suspension based in Short Time Fourier Transform. Research object it's passenger car, which front suspension have faults. A results of analysis to reveal sensitivity used method for detects to bring faults.

18

Application of theory of wavelets for analysis of EKG signal

63%

Ciepłucha M. , Jóźwik K.

Mechanics and Mechanical Engineering

|

2000

|

tom Vol. 4, nr 1

31--38

EN

Application of Wavelet Theory for detection of P-wave, reduction of floating izoelectric line, monitoring of changes in EKG signal and compression of EKG signal is presented. Signals of biologic origin, like EKG signal, are wideband signals and methods such as Short Time Fourier Transform (STFT), utilizing narrowband basis functions, are not suitable for representation of these signals. Wavelet Theory, which provides for wideband representation of signals, uses a special analysis window, called mother wavelet, to analyze local spectral information of the EKG signal. The mother wavelet is either compressed or dilated to give multiresolution signal representation. Results of application of Continues Wavelet Transform (CWT) and Discrete Wavelet Transform (DWT) shows good efficiency in P-wave detection in noisy EKG signal and benefits of multiresolution analysis in eliminating unwanted frequency components, monitoring of EKG changes and reduction of redundant samples in e EKG signal.

19

Infrared devices and techniques (revision)

51%

Rogalski A. , Chrzanowski K.

Metrology and Measurement Systems

|

2014

|

tom Vol. 21, nr 4

565--618

EN

The main objective of this paper is to produce an applications-oriented review covering infrared techniques and devices. At the beginning infrared systems fundamentals are presented with emphasis on thermal emission, scene radiation and contrast, cooling techniques, and optics. Special attention is focused on night vision and thermal imaging concepts. Next section concentrates shortly on selected infrared systems and is arranged in order to increase complexity; from image intensifier systems, thermal imaging systems, to space-based systems. In this section are also described active and passive smart weapon seekers. Finally, other important infrared techniques and devices are shortly described, among them being: non-contact thermometers, radiometers, LIDAR, and infrared gas sensors.

20

Diagnosis of ITSC fault in the electrical vehicle powertrain system through signal processing analysis

51%

Ouamara D. , Boukhnifer M. , Chaibet A. , Maidi A.

Diagnostyka

|

2023

|

tom Vol. 24, No. 1

art. no. 2023113

EN

The three-phase induction motor is well suited for a wide range of mobile drives, specifically for electric vehicle powertrain. During the entire life cycle of the electric motor, some types of failures can occur, with stator winding failure being the most common. The impact of this failure must be considered from the incipient as it can affect the performance of the motor, especially for electrically powered vehicle application. In this paper, the intern turn short circuit of the stator winding was studied using Fast Fourier transform (FFT) and Shor-Time Fourier transform (STFT) approaches. The residuals current between the estimated currents provided by the extended Kalman filter (EKF) and the actual ones are used for fault diagnosis and identification. Through FFT, the residual spectrum is sensitive to faults and gives the extraction of inter-turn short circuit (ITSC) related frequencies in the phase winding. In addition, the FFT is used to obtain information about when and where the ITSC appears in the phase winding. Indeed, the results allow to know the faulty phase, to estimate the fault rate and the fault occurrence frequency as well as their appearance time.