Wyniki wyszukiwania - BazTech

1

Analysis of the single stage cycloidal gearbox with lobe defects. Fault diagnosis attempts using coherence function and Morris minimum-bandwidth wavelets

Król Roman

Archive of Mechanical Engineering

|

2023

|

LXX, nr 3

409--431

EN

In this article, the frequency characteristics of the forces and torques in the various cycloidal gearbox designs were investigated. The aim of the article is the search for frequency patterns that could be used in the formulation of a fault diagnosis methodology. Numerical analysis was performed in the cycloidal gearbox without defects as well as in cycloidal gearboxes with lobe defects or with removed lobes. The results of the numerical analysis were obtained in the multibody dynamics model of the cycloidal gearbox, implemented in Fortran and using the 2nd-order Runge-Kutta method for the integration of the motion equations. The used model is planar and uses Hunt and Crossley’s nonlinear contact modelling algorithm, which was modified using the Heaviside function and backlash to fit cycloidal gearbox model convergence demands. In the analysis of fault diagnosis methods, the coherence function and Morris minimum-bandwidth wavelets were used. It is difficult to find a unique pattern in the results to use in the fault diagnosis because of the random characteristics of the torques at the input and output shafts. Based on obtained results, a promising, low-vibration cycloidal gearbox design with removed 7 lobes of the single wheel was studied using the FFT algorithm.

2

Monitoring of helicopter swash-plate wear using the FAM-C diagnosis method

Gębura Andrzej, Kowalczyk Henryk, Tokarski Tomasz, Handzel Kacper, Klimaszewski Sławomir Jerzy, Zgrzywa Franciszek

Diagnostyka

|

2022

|

Vol. 23, No. 1

art. no. 2022104

EN

Helicopter rotor dynamics (blade vibrations, ground resonance, influence of forward speed, etc.) play an important role in the wear and tear of the transmission system and power unit. Particularly fast wear of these components is to be expected in military helicopters in combat conditions, where the flight dynamics parameters are often exceeded. The FAM-C method developed at the Air Force Institute of Technology in Poland has been used to assess and monitor this wear. This method can be used to monitor damage to helicopter propulsion and transmission, where other "classical" methods are less effective due to a very complicated system of forces, variable as to the direction of amplitude and frequency, causing vibrations in closely spaced kinematic pairs. For this reason, vibroacoustic and thermal effects are created around these kinematic pairs, which interfere with each other. In a helicopter, the propulsion unit, including the power transmission unit, is at the same time the carrier unit. This has forced designers to construct a propulsion system with a much greater number of joints and bearing supports. This article presents the possibilities of the FAM-C method for monitoring of swash-plate main bearing wear. The swash-plates are not formally part of the helicopter's propulsion unit but are used to direct the thrust vector of the blades i.e., they direct the helicopter's power vector. Since during this process their components are observable by the FAM-C method, the authors found it necessary to include issues related to their diagnosis in this study. In the FAM-C method, the signal from the AC generator during the normal operation of the helicopter is processed. Analysis of this signal allows simultaneous monitoring of multiple engine and transmission components simultaneously. It does not require any separate sensors for this purpose - one "full-time" alternator or tachometer generator is - with proper collection and processing of the output voltage signal - the source of a whole range of diagnostic information. Thus, one generator is an observer of the technical condition of many elements of the power unit simultaneously. What's more, the signal can be collected from any place in the electrical network, which makes it possible to install the measuring system in safe locations, even while the power train is running. Some examples of diagnostic symptoms leading to wear detection are described. Research based on analysis of these findings with the use of the FAM-C method is described in the paper. In the FAM-C method, signal from the AC generator used in routine operation of the helicopter is processed. Signal analysis enables simultaneous monitoring of several engine and transmission elements. Some examples of diagnostic symptoms used to detect wear are described in the paper.

3

Investigations on an influence of the material properties on vibrations of active rocker-bogie suspension

Sokół Krzysztof, Pierzgalski Maciej

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2022

|

Vol. 70, nr 1

art. no. e138239

EN

Unmanned vehicles are often used in everyday life, mostly by rescue teams or scientists exploring new terrains. In those constructions, the suspension has constant dimensions, which leads to many disadvantages and limits the application area. The solution to these problems can be creating a six-wheeled mobile platform that can dynamically change the wheelbase in relation to the area of action or terrain inclination angle. The active change in location of the center of gravity gives a possibility to access sloppy obstacles not available with classical suspensions. The main scope of this study is to investigate the influence of material properties on vibration frequency at different lengths of suspension members. The obtained results will allow finding the optimum material for producing a prototype unit.

4

Free vibration analysis of imperfect functionally graded sandwich plates: analytical and experimental investigation

Njim E.K., Bakhy S.H., Al-Waily M.

Archives of Materials Science and Engineering

|

2021

|

Vol. 111, nr 2

49--65

EN

Purpose: This paper develops a new analytical solution to conduct the free vibration analysis of porous functionally graded (FG) sandwich plates based on classical plate theory (CPT). The sandwich plate made of the FGM core consists of one porous metal that had not previously been taken into account in vibration analysis and two homogenous skins. Design/methodology/approach: The analytical formulations were generated based on the classical plate theory (CPT). According to the power law, the material properties of FG plates are expected to vary along the thickness direction of the constituents. Findings: The results show that the porosity parameter and the power gradient parameter significantly influence vibration characteristics. It is found that there is an acceptable error between the analytical and numerical solutions with a maximum discrepancy of 0.576 % at a slenderness ratio (a/h =100), while the maximum error percentage between the analytical and experimental results was found not exceeding 15%. Research limitations/implications: The accuracy of analytical solutions is verified by the adaptive finite elements method (FEM) with commercial ANSYS 2020 R2 software. Practical implications: Free vibration experiments on 3D-printed FGM plates bonded with two thin solid face sheets at the top and bottom surfaces were conducted. Originality/value: The novel sandwich plate consists of one porous polymer core and two homogenous skins which can be widely applied in various fields of aircraft structures, biomedical engineering, and defense technology. This paper presents an analytical and experimental study to investigate the free vibration problem of a functionally graded simply supported rectangular sandwich plate with porosities. The objective of the current work is to examine the effects of some key parameters, such as porous ratio, power-law index, and slenderness ratio, on the natural frequencies and damping characteristics.

5

Planning of the experiment for the defining of the technical state of the transformer by using amplitude-frequency characteristic

Rubanenko Oleksandr, Grishchuk Maksim, Rubanenko Olena

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 3

118--124

EN

The article analyzes existing methods of diagnosing power transformers (PTs). The technique of experiment planning using D-optimal plans is investigated. According to the results of the study, a D-optimal plan of the frequency response measurements was created, which defines the algorithm of the studies. On the example of PT type TMG 1000/10 it is determined that 13 measurements are required to evaluate the condition of the PT during the interpretation of the results of the frequency response measurements. The method of determining the average frequency characteristic of PT is given. This amplitude-frequency characteristic can be used to check the PT status and to detect damage at an early stage of their development.

PL

Artykuł analizuje istniejące metody diagnozowania transformatorów mocy (TM). Badana jest technika planowania eksperymentu z wykorzystaniem planów optymalnych. Zgodnie z wynikami badań opracowano optymalny D-plan pomiarów odpowiedzi częstotliwościowej, który określa algorytm badań. Na przykładzie TM typu TMG 1000/10 ustalono, że do oceny stanu TM podczas interpretacji wyników pomiarów odpowiedzi częstotliwościowej potrzeba 13 pomiarów. Podano metodę wyznaczania charakterystyki średniej częstotliwości TM. Ta charakterystyka amplitudowo-częstotliwościowa może być u żywana do sprawdzania stanu TM i wykrywania uszkodzeń na wczesnym etapie ich rozwoju.

6

Monitoring of electric arc furnace supply voltage frequency using phasor analysis

Barczentewicz Szymon, Duda Krzysztof, Bień Andrzej

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 5

51--54

EN

This paper presents the results of measurement experiment conducted in the operating steel plant. Frequency analysis of measured signals revealed an interesting phenomenon, as it happened that after switching off the electric arc furnace, the frequency of the supplying voltage and current increased slightly instead of decreasing, as we would normally expect. This abnormal frequency behaviour was identified by phasor analysis and also confirmed by the DTFT (Discrete Time Fourier Transform) analysis, and the MatrixPencil analysis.

PL

Artykuł prezentuje wyniki eksperymentu wykonanego w hucie stali. Analiza częstotliwości ujawniła ciekawe zjawisko, w którym po wyłączeniu pieca łukowego częstotliwości napięcia i prądu w wewnętrznej części huty zmniejszyła się zamiast zwiększyć, jak można by się spodziewać. To nieoczekiwane zjawisko zostało zarejestrowane z pomocą PMU i potwierdzone przez transformację Fouriera dla sygnałów dyskretnych oraz analizę MatrixPencil.

7

The fractional Fourier transform as a biomedical signal and image processing tool: A review

Gómez-Echavarría Alejandro, Ugarte Juan P., Tobón Catalina

Biocybernetics and Biomedical Engineering

|

2020

|

Vol. 40, no. 3

1081--1093

EN

This work presents a literature review of the fractional Fourier transform (FrFT) investiga-tions and applications in the biomedical field. The FrFT is a time-frequency analysis tool that has been used for signal and image processing due to its capability in capturing the nonstationary characteristics of real signals. Most biomedical signals are an example of such non-stationarity. Thus, the FrFT-based solutions can be formulated, aiming to enhance the health technology. As the literature review indicates, common applications of the FrFT involves signal detection, filtering and features extraction. Establishing adequate solutions for these tasks requires a proper fractional order estimation and implementing the suitable numeric approach for the discrete FrFT calculation. Since most of the reports barely describe the methodology on this regard, it is important that future works include detailed information about the implementation criteria of the FrFT. Although the applications in biomedical sciences are not yet among the most frequent FrFT fields of action, the growing interest of the scientific community in the FrFT, supports its practical usefulness for developing new biomedical tools.

8

Monitorowanie częstotliwości pieca łukowego wykorzystujące technikę fazorową

Barczentewicz Szymon, Duda Krzysztof, Bień Andrzej

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

|

2019

|

Nr 67

115--118

PL

Artykuł prezentuje wyniki eksperymentu wykonanego w hucie stali. System pomiarowy wykorzystany do przeprowadzenia pomiarów jest oparty na systemie czasu rzeczywistego z układem FPGA, który pozwala na wykonanie pomiarów sygnałów analogowych. Trzy fazy napięcia i prądu zostały zmierzone w trzech wybranych punktach sieci zasilającej. Analiza częstotliwości ujawniła ciekawe zjawisko, w którym po wyłączeniu pieca łukowego częstotliwości napięcia i prądu w wewnętrznej części huty zmniejszyła się zamiast zwiększyć, jak można by się spodziewać. To nieoczekiwane zjawisko zostało zarejestrowane z pomocą PMU i potwierdzone przez analizę MatrixPencil. Przeprowadzone pomiary potwierdziły zasadność monitorowania częstotliwości napięcia zasilania pieców łukowych za pomocą analizy fazora.

EN

This paper presents the results of measurement experiment conducted in the operating steel plant. The measurement system was built with real time system with FPGA module, capable of measuring analog signals. Three phase voltages and currents were acquired in three selected points of supplying power network. Frequency analysis of measured signals revealed an interesting phenomenon, as it happened that after switching off the electric arc furnace, the frequency of the supplying voltage and current increased slightly instead of decreasing, as we would normally expect. This abnormal frequency behavior was identified by phasor analysis and also confirmed by DTFT (Discrete Time Fourier Transform) analysis, and MatrixPencil analysis. Performed measurements proved phasor analysis to be a useful application for electric arc furnace frequency monitoring.

9

Advanced time-frequency representation in voice signal analysis

Mika Dariusz, Józwik Jerzy

Advances in Science and Technology. Research Journal

|

2018

|

Vol. 12, no 1

251--259

EN

The most commonly used time-frequency representation of the analysis in voice signal is spectrogram. This representation belongs in general to Cohen’s class, the class of time-frequency energy distributions. From the standpoint of properties of the resolution, spectrogram representation is not optimal. In Cohen class representations are known which have a better resolution properties. All of them are created by smoothing the Wigner-Ville’a distribution characterized by the best resolution, however, the biggest harmful interference. The used smoothing functions decide about a compromise between the properties of resolution and eliminating harmful interference term. Another class of time-frequency energy distributions is the affine class of distributions. From the point of view of readability of analysis of the best properties are known so called Redistribution of energy caused by the use of a general methodology referred to as reassignment to any time-frequency representation. Reassigned distributions efficiently combine a reduction of the interference terms provided by a well adapted smoothing kernel and an increased concentration of the signal components.

10

Stratigraphic absorption compensation based on multiscale shearlet transform

Liu C., Wang D., Sun J., Li Y., Yang F.

Acta Geophysica

|

2018

|

Vol. 66, no. 4

575--584

EN

Seismic waves propagating through viscoelastic media experience stratigraphic absorption and attenuation effects, which directly affect the imaging resolution in seismic exploration. Without stratigraphic absorption, the ratio of deep reflection energy to shallow reflection energy (attenuation ratio) is invariable at different frequencies. If a seismogram is decomposed into different frequency bands, these signals will show similar time–energy distributions. Therefore, the attenuation ratios should be similar across different frequency bands, except for frequency-variable weights. Nevertheless, the frequencyvariable weights for different frequency bands can be obtained by benchmarking against the time–energy distributions of low-frequency information because the loss of low-frequency information is relatively insignificant. In this light, we obtained frequency-variable weights for different frequencies and established a stratal absorption compensation (SAC) model. The anisotropic basis of the shearlet enables nearly optimal representation of curved-shape seismic signals, and shearlets at different scales can represent signals for different frequency bands. Then, we combined the SAC model with the shearlet transform and established the new compensation method. As the signal and noise have different distributions in the shearlet domain, we selectively compensated the signals using a thresholding algorithm. Hence, it was possible to avoid noise enhancement. This is the prominent advantage of the proposed method over other compensation methods.

11

Trend i szum w częstotliwościowej analizie sygnałów pomiarowych

Łucyk C.

Wiadomości Elektrotechniczne

|

2013

|

R. 81, nr 9

12--16

PL

Przedstawiono oryginalną metodę identyfikacji składników harmonicznych sygnału pomiarowego oraz określono estymaty i niepewności pomiaru harmonicznych sygnału.

EN

The paper presents an original method for identification of harmonic components of measurement signal, estimates and measurement uncertainty are determined.

12

Frequency analysis of composite annular membranes

Zamorska I., Kukla S., Siedlecka U.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2012

|

Vol. 11, nr 1

129-135

EN

In this paper, the free vibration of an annular membrane consisting of three concentric segments is considered. The frequency equation and mode shapes are obtained by the use of the Green's function method. A numerical example to vibration problem of nonhomogeneous annular membrane is presented.

13

Frequency Analysis with Cross-Correlation Envelope Approach

Kotowski A.

Acta Mechanica et Automatica

|

2012

|

Vol. 6, no. 4

27-31

EN

A new approach for frequency analysis of recorded signals and readout the frequency of harmonics is presented in the paper. The main purpose has been achieved by the cross$correlation function and Hilbert transform. Using the method presented in the paper, there is another possibility to observe and finally to identify single harmonic apart from commonly used Fourier transform. Identification of the harmonic is based on the effect of a straight line of the envelope of the cross$correlation function when reference and signal harmon$ ic have the same frequency. This particular case is the basis for pointing the value of the frequency of harmonic component detected.

14

Application of Green's function method in frequency analysis of axisymmetric vibration of annular plates with elastic ring supports

Kukla S., Szewczyk M.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2005

|

Vol. 4, nr 1

79-86

EN

The paper concerns the axisymmetric vibration of annular plates with concentric elastic ring supports. The formulation and solution to the problem take into account the plates with one edge clamped and another one free and arbitrary number of circular supports. The Green's function method is applied to obtain the exact solution of the problem in an analytical form. Presented numerical examples show the influence of the parameters characterizing the system on its free vibration frequencies.

15

Przestrzenny model przenośnika taśmowego masy formierskiej

Strzałko J., Grabski J.

Archiwum Odlewnictwa

|

2005

|

R. 5, nr 17

459--464

PL

W pracy jest przedstawiony przestrzenny model pozwalający na analizę odkształceń w elementach przenośnika taśmowego do masy formierskiej. Umożliwia on analizę drgań własnych układu złożonego z taśmy, bębna napędowego, bębna napinającego i krążników.

EN

In the work two discrete model of belt conveyor are presented. First one (multibody model) allows steady state and transient analysis of the conveyor planar motion. Second model (FEM) is used in the free vibration analysis.

16

Frequency analysis of a non-uniform rod by using the green’s function method

Zamojska I., Kukla S.

Vibrations in Physical Systems

|

2004

|

Vol. 21

431--434

17

An analysis of the roughness of flat surfaces generated by end-milling cutters

Miko E.

Metrology and Measurement Systems

|

2004

|

Vol. 11, nr 3

245-257

EN

This paper is concerned with the influence of the cutting speed on the longitudinal and lateral irregularities of flat surfaces sculptured with a CNC milling machine. A scanning microscope was used for registering and analyzing the morphology of milled surfaces. SEM photographs of surfaces with longitudinal and lateral profiles are included and analyzed. The measurements and the complex profile analyses discussed here were performed on a computer-aided test stand. It has been established that the effect of the cutting speed on the roughness of surface profiles is significant. The parameters related to the roughness height and shape are greater for a longitudinal profile than for a lateral one.

PL

Przedstawiono wpływ prędkości skrawania na chropowatość wzdłużną i poprzeczną powierzchni płaskich obrobionych frezami palcowymi na frezarce CNC. Przedstawiono zdjęcie morfologii powierzchni frezowanej wykonane na mikroskopie skaningowym oraz dokonano jego analizy. Umieszczono również zdjęcie skaningowe powierzchni wraz z jego profilami wzdłużnymi i poprzecznymi oraz dokonano ich analizy częstotliwościowej. Przeprowadzone badania za pomocą skomputeryzowanego stanowiska badawczego do pomiaru i kompleksowej analizy profili powierzchni wykazały istotność wpływu prędkości skrawania na chropowatość powierzchni. Otrzymano większe parametry wysokościowe i parametry opisujące kształt nierówności profilu wzdłużnego jak poprzecznego.

18

Voltage-current equations of power electronic matrix converters in frequency domain

Sobczyk T. J.

Archives of Electrical Engineering

|

2002

|

Vol. 51, nr 1

105-114

EN

The paper presents an analysis of voltages and currents in the matrix converter, which directly (without any intermediate DC link) transforms the N-phase system with frequency f1 to the M-phase system with frequency f2. Relations between input and output voltages and currents have been investigated in the frequency domain, using the symmetrical component approach. For a chosen control strategy of switching of converter semiconductor elements, the Fourier spectra of input and output voltages and currents have been determined and relations between them have been found. It has been proved that the voltages and currents on both sides of the converter are symmetrical, which is the main result of the paper.

PL

W pracy jest przedstawiona analiza napięć i prądów przekształtnika macierzowego, którego celem jest bezpośrednie (bez pośrednictwa prądu stałego) przekształcanie N-fazowego układu napięć i prądów o częstotliwości f1 w układ M-fazowy o częstotliwości f2. Aby opisać związki między napięciami i prądami na wejściu i wyjściu przekształtnika, przeprowadzono analizę w dziedzinie częstotliwości, używając do opisu wielofazowych składowych symetrycznych. Dla wybranej strategii przełączania półprzewodnikowych elementów przekształtnika dokonano analizy widm Fouriera napięć i prądów na wejściu i wyjściu oraz podano związki pomiędzy nimi. Najważniejszym rezultatem pracy jest wykazanie, że przy tej strategii sterowania napięcia i prądy po obu stronach zachowują symetrię.