Wyniki wyszukiwania - BazTech

1

Detection and identification of nonlinear contact dynamics at workpiece clamping positions

Feng Qi, Maier Walther, Braun Steffen, Möhring Hans-Christian

Journal of Machine Engineering

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2023

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Vol. 23, No. 1

114--122

EN

All mechanical systems behave nonlinearly to a certain extent since there are always reasons for nonlinearities, such as friction and slip effects, in the actual structures. It is important to detect and identify the nonlinearity due to friction and contact in order to investigate their effect on the global behavior of the workpiece-fixture system. That is a prerequisite for modeling the dynamic contact behavior at the interface between the workpiece and clamping elements. In this research, the workpiece-fixture system was excited with a shaker using the swept sine signal. The nonlinearities could be detected by comparing and analyzing the frequency responses of the structures in Bode plots. However, the nonlinearities behaved differently at various frequencies within the observation range. Different mechanisms such as nonlinear stiffness and damping, micro-slip friction, are responsible for that. Then the nonlinear contact behavior at the clamping positions was successfully identified by means of the Hilbert transform. In addition, the clamping force directly influenced the nonlinear stiffness of the workpiece-fixture system.

2

Detection of defects in a bearing by analysis of vibration signals

Bouaouiche Karim, Menasria Yamima, Khalifa Dalila

Diagnostyka

|

2023

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Vol. 24, No. 2

art. no. 2023203

EN

This work presents the analysis of vibration signals by an approach consists of several mathematical tools more elaborate such as the Hilbert transform, kurtogram, which allows the detection of vibration defects in a simple and accurate way. The steps or methods inserted in the process one complementary to the other as scalar indicators generally used in monitoring to follow the evolution of the functioning of a machine when an abnormal functioning it must make a diagnosis to detect the failing element through the use of a process. The determination of the defective organs at an optimal time is a very important operation in the industrial maintenance, which keeps the equipment in a good condition and ensures the assiduity of work. To see the effectiveness of fault detection by the proposed approach by analyzing the real vibration signals of a bearing type 6025-SKF available on the Case Western Reserve University platform.

3

Diffraction enhancement using the double sparse dictionary method

Wang Tao, Peng Suping, Lin Peng, Cui Xiaoqin, Zhou Jiawei

Acta Geophysica

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2023

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Vol. 71, no. 3

1259--1271

EN

Seismic diffraction delivers high-precision imaging of subsurface discontinuities and objects. As diffraction is characterised by weak energy, separating diffraction from full wavefields is an essential pre-imaging step. However, traditional diffraction separation methods generally produce unsatisfactory separation results for datasets with low signal-to-noise ratios. Accordingly, we propose a novel diffraction separation method that incorporates plane-wave destruction and the double sparse dictionary algorithm to improve separation quality. The plane-wave destruction method is used to suppress strong reflection, whereas the double sparse dictionary can simultaneously extract diffracted signals. A robust plane-wave destruction method using the Hilbert transform is employed to improve the stability and accuracy of slope estimation. The double sparse dictionary algorithm has better performance when sparsely representing seismic signals and can effectively extract weak diffraction with a high signal-to-noise ratio. Synthetic and field examples demonstrate the effectiveness of the proposed method in removing strong reflection and enhancing weak diffraction. Overall, the proposed method is conducive to detect small structures and offers a new resource for seismic structural interpretation.

4

On Strongly Orthogonal Martingales in Umd Banach Spaces

Yaroslavtsev Ivan S.

Probability and Mathematical Statistics

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2021

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Vol. 41, Fasc. 1

153--171

EN

In the present paper we introduce the notion of strongly orthogonal martingales. Moreover, we show that for any UMD Banach space X and for any X-valued strongly orthogonal martingales M and N such that N is weakly differentially subordinate to M, one has, for all 1 < p < 1, [formula] with the sharp constant χp;X being the norm of a decoupling-type martingale transform and lying in the range, [formula], where βp;X is the UMDp constant of X, hp;X is the norm of the Hilbert transform on Lp(R; X), [formula] are the Gaussian decoupling constants.

5

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

Adamczyk Krzysztof, Polak Adam G.

Metrology and Measurement Systems

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2021

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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.

6

Asynchronous Demodulation Method for Four SSB arranged on Frequency Axis in Mobile Radio Path using Hilbert Transform

Daikoku Kazuhiro

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 3

445--450

EN

In this paper, an asynchronous demodulation method for a four-single sideband (SSB) signal arranged on the frequency axis is developed to support burst mode transmission in a mobile radio path and to achieve greater data throughputs. When a reduced pilot carrier is placed at the center of the 4-SSB signal, it is guarded by lower and upper sidebands, that is, this scheme is classified into a tone-in-band (TIB) system. Digital signal processing (DSP) processors are useful for implementing a Hilbert transform. However, we have for a long time neglected introducing it into the demodulation process of SSB signals.

7

Comparison of Amplitude Variations of Seasonal and Sub-Seasonal Oscillations in Length of Day and Total Solar Irradiance

Kosek Wiesław, Gabryszuk Justyna

Journal of Ecological Engineering

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2020

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Vol. 21, nr 7

52--57

EN

The aim of the study was to identify and compute oscillations in two different time series with similar amplitude variations using length of day data with tide model removed (LODR) and total solar irradiance (TSI) data. The combination of the Fourier transform band pass filter and Hilbert transform allows detecting amplitude variations as a function of the oscillation period. The amplitude variations in two different time series enable computation of frequency dependent or time-frequency correlation coefficients between them. It allows also identifying such oscillations in two time series which have similar amplitude variations. The method applied to LODR and TSI data, enable to detect a possible relationship between them. This comparison method can be applied to any time series which consist of oscillations with non-constant amplitudes.

8

Identyfikacja wybranych parametrów źródeł wahań napięcia z wykorzystaniem ulepszonej empirycznej transformaty falkowej

Kuwałek Piotr

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

|

2019

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Nr 66

33--36

PL

W artykule przedstawiono wyniki wstępnych badań dotyczących nowatorskiej metody pozyskiwania informacji o wybranych parametrach źródeł wahań napięcia z wykorzystaniem ulepszonej empirycznej transformaty falkowej. Dla przeprowadzonych badań założono, że oddziaływanie źródeł wahań napięcia można identyfikować jako modulację amplitudową sygnału napięcia. Uwzględniając to założenie, daną wejściową dla ulepszonej empirycznej transformaty falkowej była obwiednia sygnału napięciowego, wyznaczona z zastosowaniem transformaty Hilberta. Poprawność działania metody zweryfikowano w oparciu o wykonane symulacje numeryczne dla sygnału deterministycznego z wykorzystaniem programu MATLAB.

EN

The article presents the results of preliminary research on an innovative method of analysis of voltage fluctuation sources with the use of an enhanced empirical wavelet transform. For the tests, it was assumed that the influence of voltage fluctuation sources can be identified as the amplitude modulation of the voltage signal. Given this assumption, the input data for the enhanced empirical wavelet transform was a voltage signal envelope derived from the use of the Hilbert transform. The correctness of the method was verified on the basis of performed simulation tests for a deterministic signal using the MATLAB program.

9

An integrative approach to analyze EEG signals and human brain dynamics in different cognitive states

Davis J. J., Lin C. -T., Gillett G., Kozma R.

Journal of Artificial Intelligence and Soft Computing Research

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2017

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Vol. 7, No. 4

287--299

EN

Electroencephalograph (EEG) data provide insight into the interconnections and relationships between various cognitive states and their corresponding brain dynamics, by demonstrating dynamic connections between brain regions at different frequency bands. While sensory input tends to stimulate neural activity in different frequency bands, peaceful states of being and self-induced meditation tend to produce activity in the mid-range (Alpha). These studies were conducted with the aim of: (a) testing different equipment in order to assess two (2) different EEG technologies together with their benefits and limitations and (b) having an initial impression of different brain states associated with different experimental modalities and tasks, by analyzing the spatial and temporal power spectrum and applying our movie making methodology to engage in qualitative exploration via the art of encephalography. This study complements our previous study of measuring multichannel EEG brain dynamics using MINDO48 equipment associated with three experimental modalities measured both in the laboratory and the natural environment. Together with Hilbert analysis, we conjecture, the results will provide us with the tools to engage in more complex brain dynamics and mental states, such as Meditation, Mathematical Audio Lectures, Music Induced Meditation, and Mental Arithmetic Exercises. This paper focuses on open eye and closed eye conditions, as well as meditation states in laboratory conditions. We assess similarities and differences between experimental modalities and their associated brain states as well as differences between the different tools for analysis and equipment.

10

An efficient wavelet-based automated R-peaks detection method using Hilbert transform

Rakshit M., Das S.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 3

566--577

EN

Machine-aided detection of R-peaks is becoming a vital task to automate the diagnosis of critical cardiovascular ailments. R-peaks in Electrocardiogram (ECG) is one of the key segments for diagnosis of the cardiac disorder. By recognizing R-peaks, heart rate of the patient can be computed and from that point onwards heart rate variability (HRV), tachycardia, and bradycardia can also be determined. Most of the R-peaks detectors suffer due to non-stationary behaviors of the ECG signal. In this work, a wavelet transform based automated R-peaks detection method has been proposed. A wavelet-based multiresolution approach along with Shannon energy envelope estimator is utilized to eliminate the noises in ECG signal and enhance the QRS complexes. Then a Hilbert transform based peak finding logic is used to detect the R-peaks without employing any amplitude threshold. The efficiency of the proposed work is validated using all the ECG signals of MIT-BIH arrhythmia database, and it attains an average accuracy of 99.83%, sensitivity of 99.93%, positive predictivity of 99.91%, error rate of 0.17% and an average F-score of 0.9992. A close observation of the simulation and validation indicates that the suggested technique achieves superior performance indices compared to the existing methods for real ECG signal.

11

Decomposition of mechanical vibration signals – the Hilbert- Huang Transform in the time domain and the Fourier Transform in the frequency domain

Gawędzki W.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 11

67--70

EN

The investigation results concerning comparisons of effects of the application of the Hilbert-Huang Transform (HHT), Fourier Transform (FT) and Short Time Fourier Transform (STFT) for the vibration signals decomposition, are presented in this paper. The record of the vibration accelerations signals of the electric torque tool was applied in investigations. It was shown that the FT transform, often applied in practice for vibration signals analysis can provide uncertain or erroneous information. Thus, it requires verifications by means of other methods, e.g. STFT or HHT.

PL

W artykule przedstawiono wyniki badań dotyczących porównania skutków zastosowania do dekompozycji sygnałów drgań transformacji Hilberta Huanga HHT, Fouriera FT oraz krótko-czasowej transformacji Fouriera STFT (Short Time Fourier Transform). Do badań wykorzystano zapis przykładowych sygnałów przyspieszeń drgań zakrętarki elektromechanicznej.

12

Budeanu’s concept of reactive and distortion power revisited

Jeltsema D.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 4

68--73

EN

Budeanu’s concept of reactive and distortion power for systems operating under nonsinusoidal conditions has been subject to criticism throughout the past decades, which finally led to its removal from the latest standards. Recently, some new results are presented that shed a different light on Budeanu’s reactive power and its compensation. In this paper, a further analysis is presented to reveal the possibility to endow Budeanu’s reactive and distortion powers with physical meaning. For linear and time-invariant systems it is shown that Budeanu’s reactive power is representing the mean value of the moving average of the difference between the total magnetic and the electric energy. Budeanu’s distortion power, after an appropriate decomposition, represents a measure of the power fluctuations around the active power and Budeanu’s reactive power.

PL

Teoria Budeanu dotycząca mocy w obwodach niesinusoidalnych była w ostatnich latach krytykowana i w rezultacie usunięta z norm. Obecnie wraca się do niektórych elementów tej teorii. W artykule zaprezentowano analizę wskazującą w jakich warunkach teoria Budeanu może być stosowana. Po odpowiedniej dekompozycji moc odkształcona jest miara˛ fluktuacji mocy wokół wartości średniej mocy czynnej i mocy biernej wg Budeanu.

13

Badanie dokładności rekonstrukcji powierzchni z interferogramu światła białego z wykorzystaniem metod bazujących na transformacie Hilberta

Wrzuszczak M., Khoma A.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 4

210--215

PL

W pracy opisano metody rekonstrukcji profilu powierzchni z interferogramu światła białego. Po krótkim wprowadzeniu do teorii sygnałów analitycznych, zaproponowano cztery metody rekonstrukcji profilu powierzchni wykorzystujące dyskretną transformatę Hilberta. Przedstawiono wyniki badań dokładności tych metod na przykładzie rekonstrukcji powierzchni płaskiej pochyłej oraz kulistej.

EN

The paper describes methods of surface profile reconstruction from the white light interferogram. The theoretical basis for a theory of analytical signals are given. Four methods for the reconstruction of the surface profile using a discrete Hilbert transform are offered. The accuracy analyses of these methods are presented on an example of the slant planar surface and spherical surface reconstruction.

14

P-wave interaction with a pair of rigid strips embedded in an orthotropic strip

Basu S., Mandal S. C.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 2

579--592

EN

The present paper is concerned with the problem of scattering of the P-wave by two co- -planer finite rigid strips placed symmetrically in an infinitely long orthotropic strip. Using the Hilbert transform technique, the mixed boundary value problem has been reduced to the solution of dual integral equations which has finally been reduced to the solution of a Fredholm integral equation of the second kind. Solving this integral equation numerically, stress intensity factors have been calculated at the inner and outer edges of the rigid strips, and the vertical displacement outside the strips has been calculated and plotted graphically to show the effect of material orthotropy.

15

Identification of modal parametrs of transmission towers

Lech Ł., Iwaniec M., Iwaniec J.

Diagnostyka

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2016

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Vol. 17, No. 4

33--38

EN

The paper presents theoretical basis for identification of nonlinear systems using the method based on Hilbert transform. Discussed method was verified by analyzing the synthesized signals of known parameters. Developed and verified mathematical tools were used for analysis of dynamic responses of the real object: a laboratory (physical) model of the transmission tower. For the considered laboratory model it was possible to simulate damages of individual truss elements and observe changes in system dynamic characteristics. Results of the carried out research proved that the first natural frequency and damping factor change in the observable extent as a result of damage presence.

PL

W pracy przedstawione zostały teoretyczne podstawy identyfikacji układów nieliniowych z wykorzystaniem transformaty Hilberta. Omówioną metodę zweryfikowano przeprowadzając analizę syntezowanych sygnałów o znanych parametrach. Opracowany aparat matematyczny zastosowano do analizy odpowiedzi dynamicznych obiektu rzeczywistego: modelu laboratoryjnego (fizycznego) przemysłowej konstrukcji wsporczej znajdującej się w ciągłej eksploatacji. Rozpatrywany model laboratoryjny umożliwił symulowanie uszkodzeń poszczególnych elementów kratownicy i badanie ich wpływu na zmianę parametrów dynamicznych. W pracy wykazano, że w wyniku uszkodzenia układu wartości pierwszych częstotliwość drgań własnych oraz tłumienia zmieniają się w stopniu obserwowalnym.

16

Metody rekonstrukcji powierzchni z interferogramu światła białego bazujące na transformacie Hilberta

Khoma A., Manske E.

Zeszyty Naukowe Politechniki Rzeszowskiej. Elektrotechnika

|

2015

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z. 34 [292], nr 4

71--75

PL

W pracy zaprezentowano oparte na transformacie Hilberta metody rekonstrukcji profilu powierzchni nieliniowej na podstawie interferogramu światła białego. Zbadano dokładność tych metod na przykładzie rekonstrukcji powierzchni kulistej. Badania obejmowały rekonstrukcję powierzchni na podstawie modelu matematycznego interferogramu oraz oszacowanie błędu rekonstrukcji profilu. Największą dokładność uzyskano dla metody estymacji chwilowej fazy interferogramu.

EN

The paper presents methods for nonlinear surface profile reconstruction from the white light interferogram based on Hilbert transform. The accuracy of these methods was analyzed on the example of a spherical surface reconstruction. The method investigation included surface and interferogram synthesis based on the mathematical model and estimation the profile reconstruction error. The method of estimating the instantaneous phase of the interferogram showed the greatest accuracy.

17

Zastosowanie transformacji Hilbert Vibration Decomposition do analizy sygnałów parasejsmicznych w dziedzinie czasu

Gawędzki W., Serzysko B.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 8

7--10

PL

W artykule przedstawiono wyniki badań dotyczących zastosowania transformacji HVD (ang. Hilbert Vibration Decomposition) do analizy sygnałów parasejsmicznych. Przeprowadzono dekompozycję sygnałów na sumę quasi-harmonicznych składowych (modów), których amplitudy oraz częstotliwości są parametrycznymi funkcjami czasu. W przeciwieństwie do stosowanych aktualnie w diagnostyce transformacji Fouriera DFT oraz STFT nadaje się ona do analizy zjawisk o charakterze zarówno nieliniowym jak i niestacjonarnym.

EN

The article reports on investigation results of Hilbert Vibration Decomposition transformation (HVD) utilization for a paraseismic signals. The main HVD parameters are considered in the explored area. We performed signals decomposition for a sum of a quasi harmonic components that amplitudes and frequencies are parametric time functions. In contrast to commonly used in diagnostic’s DFT and STFT transformations, proposed method is suitable for non-stationary and nonlinear phenomenon’s.

18

Dekompozycja sygnałów EEG w dziedzinie czasu przy zastosowaniu transformacji Hilberta-Huanga HHT

Gawędzki W., Socha M., Sławik P.

Przegląd Elektrotechniczny

|

2015

|

R. 91, nr 5

33-36

PL

Do dekompozycji sygnałów EEG w dziedzinie czasu zastosowana została empiryczna metoda EMD (ang. Empirical Mode Decomposition), która w wersji rozszerzonej o transformację Hilberta funkcjonuje pod nazwą transformacji HHT (ang. Hilbert-Huang Transform). Transformacja ta umożliwia poprawną dekompozycję sygnału EEG na sumę quasi-harmonicznych składowych, których amplitudy oraz częstotliwości są parametrycznymi funkcjami czasu. W przeciwieństwie do stosowanych aktualnie w diagnostyce transformacji Fouriera DFT oraz STFT nadaje się ona do analizy zjawisk o charakterze zarówno nieliniowym jak i niestacjonarnym.

EN

An Empirical Mode Decomposition method extended with the Hilbert transform (Hilbert-Huang Transform) was used for EEG decomposition in time domain. This transformation allows for proper EEG signal decomposition into quasi-harmonic components that amplitudes and frequencies are time dependence functions. In contrast to commonly used in diagnostic’s DFT and STFT transformations, proposed method is suitable for non-stationary and nonlinear phenomenon’s.

19

Badania symulacyjne metod estymacji czasu opóźnienia sygnałów losowych wykorzystujących transformatę Hilberta

Hanus R., Zych M., Petryka L.

Przegląd Elektrotechniczny

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2015

|

R. 91, nr 8

15--18

PL

W artykule przedstawiono wyniki badań czterech korelacyjnych metod estymacji czasu opóźnienia, w których zastosowano transformatę Hilberta. W symulacjach wykorzystano wybrane modele wzajemnie opóźnionych sygnałów stochastycznych. Uzyskane wyniki porównano z wynikami otrzymanymi dla klasycznej korelacji wzajemnej.

EN

The article presents the research results of the four correlation time delay estimation methods, in which the Hilbert Transform is applied. In the simulations selected models of mutually delayed stochastic signals were used. The obtained results were compared with the classical crosscorrelation procedure.

20

Hilbert-Twin – A Novel Hilbert Transform-Based Method To Compute Envelope Of Free Decaying Oscillations Embedded In Noise, And The Logarithmic Decrement In High-Resolution Mechanical Spectroscopy HRMS

Magalas L. B., Majewski M.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2A

1091--1098

EN

In this work, we present a novel Hilbert-twin method to compute an envelope and the logarithmic decrement, δ, from exponentially damped time-invariant harmonic strain signals embedded in noise. The results obtained from five computing methods: (1) the parametric OMI (Optimization in Multiple Intervals) method, two interpolated discrete Fourier transform-based (IpDFT) methods: (2) the Yoshida-Magalas (YM) method and (3) the classic Yoshida (Y) method, (4) the novel Hilbert-twin (H-twin) method based on the Hilbert transform, and (5) the conventional Hilbert transform (HT) method are analyzed and compared. The fundamental feature of the Hilbert-twin method is the efficient elimination of intrinsic asymmetrical oscillations of the envelope, aHT (t), obtained from the discrete Hilbert transform of analyzed signals. Excellent performance in estimation of the logarithmic decrement from the Hilbert-twin method is comparable to that of the OMI and YM for the low- and high-damping levels. The Hilbert-twin method proved to be robust and effective in computing the logarithmic decrement and the resonant frequency of exponentially damped free decaying signals embedded in experimental noise. The Hilbert-twin method is also appropriate to detect nonlinearities in mechanical loss measurements of metals and alloys.

PL

W pracy przedstawiono nową metodę Hilbert-twin, opartą na dyskretnej transformacie Hilberta, do obliczeń obwiedni wykładniczo tłumionych sygnałów odkształceń sprężystych zawierających w sobie szum oraz do estymacji logarytmicznego dekrementu tłumienia. Przeanalizowano i porównano wyniki obliczeń uzyskane z pięciu różnych metod: (1) metoda parametryczna OMI (Optimization in Multiple Intervals), dwie metody bazujące na interpolowanej dyskretnej transformacie Fouriera (IpDFT): (2) metoda Yoshida-Magalas (YM) i (3) klasyczna metoda Yoshidy (Y), (4) nowa metoda Hilbert-twin (H-twin), którą po raz pierwszy przedstawiono w niniejszej pracy oraz (5) klasyczna metoda obliczeń obwiedni z transformaty Hilberta (HT). Zaletą i fundamentalną cechą charakterystyczną metody H-twin jest skuteczne usunięcie typowych dla dyskretnej transformaty Hilberta asymetrycznych oscylacji obwiedni. Z tego właśnie względu metoda H-twin zapewnia bardzo dobrą estymację logarytmicznego dekrementu tłumienia, która jest porównywalna z metodami OMI i YM zarówno dla niskich, jak i wysokich poziomów tłumienia. Metoda H-twin jest niewrażliwa na szum i jest wyjątkowo skuteczna w precyzyjnym wyznaczaniu logarytmicznego dekrementu tłumienia oraz częstotliwości rezonansowej wykładniczo tłumionych drgań swobodnie tłumionych zawierających szum eksperymentalny. Metoda H-twin może również służyć do detekcji i analizy efektów nieliniowych występujących w trakcie pomiarów rozpraszania energii mechanicznej w metalach i stopach metali badanych metodą spektroskopii mechanicznej.