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1

Noise effect on parameters of quiet sonar with code modulation

Salamon Roman, Marszal Jacek, Jedel Andrzej

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023109

EN

Earlier publications of the paper authors have shown that the use of code keying mixed with the CW FM sound signal allows the significant reduction in the distance measurement error, compared to classic silent CW FM sonar. In addition to the code modulation parameters, the magnitude of this error is influenced by the received input acoustic noise. The article shows the dependence of the input signal-to-noise ratio and the sound signal parameters on the target distance measurement error and the detection conditions, such as the output signal-to-noise ratio and the side lobe level. The results of the analysis were compared to the same parameters of the CW FM silent sonar without code modulation.

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

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2022

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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

Transmission Perspective on the Mechanism of Coarse and Fine Crackle Sounds

Lu Bing-Yuh, Hsueh Meng-Lun, Wu Huey-Dong

Archives of Acoustics

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2021

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Vol. 46, No. 2

289--300

EN

The possibility of a normal distribution indicates that few particles are in the same phase during a breath and their reflections can be observed on the chest wall, then a few explosive waves with relatively large power occurr occasionally. Therefore, the one-cycle sine wave which is simulated as a single burst of the explosive effect phenomenon penetrates through the chest wall and was analysed to explore the reason of the crackle sounds. The results explain the differences between the definitions of crackle proposed by Sovijärvi et al. (2000a). The crackles in the lungs were synthesised by a computer simulation. When the coarse crackles occur, the results indicate that higher burst frequency carriers (greater than 100 Hz) directly penetrate the bandpass filter to simulate the chest wall. The simulated coarse crackle sounds were low pitched, with a high amplitude and long duration. The total duration was greater than 10 ms. However, for a lower frequency carrier (approximately 50 Hz), the fundamental frequency component was filtered out. Therefore, the second harmonic component of the lower frequency carrier, i.e., the fine crackle, penetrated the chest wall. Consequently, it is very possible that the normal lung sounds may contain many crackle-shaped waves with very small amplitudes because of the filtering effects of the chest wall, environment noises, electric devices, stethoscopes, and human ears, the small crackles disappear in the auscultations. In addition, our study pointed out that some unknown crackles of the very low frequency under the bandwidth of the human ears cannot penetrate the airways and be detected by medical doctors. Therefore, it might be necessary to focus advanced electronic instrumentation on them in order to analyse their possible characteristics for diagnosis and treatment of the respiration system.

4

The wavelet as the evaluation tool of vehicles’ seat suspension system

Glowinski Sebastian, Blazejewski Andrzej

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020206

EN

In this paper, an innovative active seat suspension system for vehicles is presented. This seat suspension prototype is built with a shear guidance mechanism, an air spring, a hydraulic shock absorber and end-stop buffers. The acceleration particular signals are measured by using Inertial Measurement Units (IMUs) placed on the seat and the human head. As the excitation, the horizontal vibrations are applied. As an alternative to the classical Fourier approach, the Wavelet Transfer Function (WTF) is introduced to describe the effectiveness of particular seat suspension. In both of the system cases, the human head reaction is investigated by using the Matlab package.

5

Frequency modulation approach based on split-ring resonator loaded by varactor diode

Vovchuk Dmytro, Haliuk Serhii, Robulets Pavlo, Politanskyi Leonid

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2020

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T. 10, nr 3

74--77

EN

In the paper,anapproach tofrequency modulation is presented using a split-ring resonator (SRR) loaded by a varactor diode. The modulation occurs due to the continuous time variation of capacitance of the varactor diode via changing of its bias voltage by the signal which is necessaryto modulate. The modulation signal is used for bias voltage. As a source of a carrier signal,one more extra magnetic loop antenna is utilized whichis coupled withtheSRR via near-field interaction. Investigation of two types of signals (harmonic and chaotic) was performed for modulation in the paper. It is shownthatitis possibileto provide the frequency modulation with deviation Δfd= ±80MHz which covers the frequency range 0.95...1.11GHzfor a 1GHz carrier signal whena SMV1231varactor diode is used. The major advantages of the suggested approach are the very simple designand abilityto easily define the required values of frequency deviation through tuning of the bias voltage magnitude range of the varactor diode. Therefore, the presented investigation and results can be useful in themanufacturing of low-cost radio components.

PL

W pracy zaproponowano zasadę modulacji częstotliwości z wykorzystaniem rezonatora z dzielonym pierścieniem (SRR) obciążonego diodą pojemnościową.Proces modulacji zachodzi poprzez ciągłą zmianę pojemności diody pojemnościowej, która z kolei następujepoprzez zmianę napięcia polaryzacji. Sygnał modulujący służy jako napięcie polaryzacji.Źródłem sygnału nośnego jest dodatkowa antena magnetyczna, która oddziałuje poprzez bliskie pole magnetyczne z SRR. W pracy przeprowadzono badaniaw których jako sygnał modulującyzostały wykorzystane dwa rodzaje sygnałów: harmoniczny i deterministyczny chaotyczny.Wykazano, że przy zastosowaniu diody pojemnościowej SMV1231 i częstotliwości sygnału nośnego 1 GHz możliwe jest zapewnienie modulacji częstotliwości z odchyleniem Δfd= ±80MHzw paśmie częstotliwości 0,95... 1,11 GHz.Zaletami proponowanej metody modulacji są bardzo prosta konstrukcja i możliwość łatwego ustawienia żądanej wartości odchylenia częstotliwości poprzez dostosowanie zakresu wartości napięcia przyłożonego do diody pojemnościowej.Przedstawione badania i uzyskane wyniki mogą być przydatne w produkcji tanich komponentów radiowych.

6

Badanie rezonansów lokalnych i złożonych w lotniczych zespołach napędowych z wykorzystaniem metod FAM-C i FDM-A

Lewitowicz Jerzy, Szelmanowski Andrzej, Gębura Andrzej, Pazur Andrzej, Franczuk Edyta

Przegląd Elektrotechniczny

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2019

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R. 95, nr 11

59--62

PL

W artykule przedstawiono zagadnienia związane z badaniami lotniczych zespołów wirnikowych, a w szczególności ich łożysk tocznych i elementów przekładni zębatych. Opisano również podstawy teoretyczne badań i analizy zjawisk rezonansowych, identyfikowanych przy pomocy metod diagnostycznych FAM-C i FDM-A. Metody te oparte są na analizie modulacji napięcia wyjściowego prądnic i zapewniają monitorowanie zjawisk dynamicznych wszystkich podzespołów występujących w lotniczym zespole napędowym.

EN

The article presents the issues related to the research of aerodynamic rotor assemblies, in particular their rolling bearings and toothed gear components. The theoretical foundations of research and analysis of resonance phenomena, identified using the FAM-C and FDM-A diagnostic methods are also described. These methods are based on the analysis of generator output voltage modulation and provide monitoring of dynamic phenomena of all components found in the aviation power unit.

7

Selected problems of diagnosing toothed gears in the aspect of developing hums system

Gębura A., Stokowski M.

Journal of KONES

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2018

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Vol. 25, No. 4

517--524

EN

A diagnostic FDM-A method, based on the measurement of modulation of constituent frequency of direct current (DC) generator pulsation as well as FAM-C method, established on the measurement of frequency modulation of alternating current (AC) generator, were developed in the Air Force Institute of Technology [3, 9-10]. The essence of their accuracy lies in "natural" synchronizing of sampling with angular speed of the observed kinematic pair – if the dynamic processes of the observed object accelerate, the sampling becomes faster too [9-10]. At the same time, around the "synchronization points", due to the clearance in the power transmission there is a certain natural oscillation between the observed kinematic pair and generator’s rotor − vibrations are created. These vibrations are called jitter [9, 23] and they constitute an additional supplement to this method, because they provide more information on resolution and accuracy. Moreover, the abovementioned method enables to define the level of subassembly abrasive wear and its location in the time of normal operation of the powerplant [9-10]. This method allows also detecting resonances of elements on the basis of observation of shape and relative position of characteristic sets, which i.e. enable to calculate the mechanical quality factor of kinematic pair − it is possible to establish the operation time of kinematic pair until entering the resonance degradation. Other numerous parameters associated with the assembly of power unit rotor were also outlined: rotor skew angle, level of frictional wear of bearing cage − lack of contact of bearing components, bearing assembly ovalisation.

8

Analiza sygnałów niskiej częstotliwości do zastosowań sodarowych

Knioła M., Rogala T.

Elektronika : konstrukcje, technologie, zastosowania

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2018

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Vol. 59, nr 8

33--37

PL

Wysoka rozróżnialność w odległości i częstotliwości stanowią istotny problem zarówno w aplikacjach radarowych (RADAR, ang. Radio Detection and Ranging), jak i sodarowych (SODAR, ang. Sound Detection and Ranging). Pomimo wielu wspólnych cech systemów radarowych i sodarowych, duża różnica w zakresie częstotliwości pracy wymusza dokładną analizę emitowanych sygnałów sondujących. W artykule przedstawiono wyniki badań mających na celu określenie parametrów sygnałów złożonych odpowiedzialnych za uzyskanie odpowiedniej rozdzielczości zasięgu oraz częstotliwości przy użyciu sygnałów o niskiej częstotliwości dla aplikacji sodarowych.

EN

High range and Doppler resolution is a significant issue in both RADAR (Radio Detection and Ranging) and SODAR (Sound Detection and Ranging) applications. Despite the many common features of the RADAR and SODAR systems, a very large difference in the frequency of the signal forces a thorough analysis of the emitted probing signals. This article presents the results of research aimed at determining parameters of complex waveforms responsible for obtaining suitable range/Doppler resolution using low frequency signals for SODAR applications.

9

Monitoring the helicopter transmission using the FAM-C diagnostic method

Gębura A., Stefaniuk M.

Diagnostyka

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2017

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Vol. 18, No. 2

75--85

EN

Dynamics of the helicopter rotor (blade vibrations, ground resonance, influence of forward speed etc.) plays a significant role in wear of transmission and engine systems. Particularly severe wear of these elements can be expected on military helicopters operating in battlefield conditions, where exceedances of dynamic flight parameters and harsh maneuvers occur more frequently. The “FAM-C” diagnostic method, developed by the Air Force Institute of Technology in Poland, has been used for assessing and monitoring a fatigue wear. Particularly, this method may be applied to monitor defects of power plant and helicopter transmission system, where other “classical” methods are less efficient due to the very complex variable system as for the direction and frequency, system of forces generating vibrations in kinematic pairs situated close to each other. Due to this reasons certain vibroacoustic and thermal effects develop around these pairs and they interfere with each other. In a helicopter, a power plant, including a power transmission system is also a carrying assembly. It forced designers to construct a power plant with increased number of joints and bearing supports. This article depicts possibilities of FAM-C method regarding wear of the main bearing of helicopter rotor, wear of surface of teeth contact, clearances between axles of gear wheels in gear and the evaluation of circumferential clearances on splined connections. 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 at the same time. It doesn’t require any separate sensors – one permanent electric generator or tachometer generator is - by the appropriate way of picking up and converting the output voltage signal - a source of the whole gamut of diagnostic information.

PL

Dynamika wirnika śmigłowca (drgania łopat, rezonans przyziemny, wpływ prędkości postępowej itp.) odgrywają istotną rolę w zużywaniu systemu transmisji i zespołu napędowego. Szczególnie szybkie zużycie tych elementów należy oczekiwać śmigłowcach wojskowych w warunkach bojowych, w których to często występują przekroczenia parametrów dynamiki lotu. Metoda FAM-C opracowana w Instytucie Technicznym Wojsk Lotniczych w Polsce została użyta do oceny i monitorowania tego zużycia. W szczególności metoda ta może być używana do monitorowania uszkodzeń zespołu napędowego i transmisji śmigłowca, gdzie inne „klasyczne” metody są mniej skuteczne z uwag na bardzo skomplikowany układ zmiennych co do kierunku amplitudy i częstotliwości układ sił wywołujący wibracje w blisko siebie położonych parach kinematycznych. Z tego powodu tworzą się wokół tych par kinematycznych efekty wibroakustyczne i termiczne , które się wzajemnie zakłócają. W śmigłowcu zespół napędowy w tym zespół transmisji mocy jest jednocześnie zespołem nośnym. Wymusiło to na konstruktorach konstruowanie układu napędowego ze znacznie większa liczbą przegubów i podpór łożyskowych. W tym artykule przedstawiono możliwości metody FAM-C dotyczącej zużycia głównego łożyska wirnika nośnego, zużycia płaszczyzny styku zębów, luzów pomiędzy osiami kół zębatych w przekładni oraz oceny luzów obwodowych na połączeniach wielowypustowych. W metodzie FAM-C przetwarzany jest sygnał z generatora prądu przemiennego w czasie normalnej eksploatacji śmigłowca. Analiza tego sygnału umożliwia jednoczesne monitorowanie wielu elementów silnika i przekładni jednocześnie.

10

Diagnostic testers operating on the basis of the FAM-C method

Gębura A., Pietnoczko B., Tokarski T.

Diagnostyka

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2016

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Vol. 17, No. 3

87--94

EN

The article discusses the design and principles of operation of three diagnostic testers constructed by the authors of this study, intended for three, different aircraft propulsion units. These design have one common way of processing the original diagnostic signal - they use one FAM-C method. This method is based on natural processing of the rotational speed fluctuations of individual kinematic cells of the propulsion unit, by the on-board generator into frequency modulations. The method, thanks to its properties, is extremely beneficial for the automatic digital diagnostic processing. The tester can be connected at any, convenient for the crew, location of the power grid, away from dangerous zones of the aircraft.

PL

W artykule omówiono konstrukcję i zasadę działania trzech testerów diagnostycznych skonstruowanych przez autorów niniejszego opracowania przeznaczonych do trzech różnych lotniczych zespołów napędowych. Konstrukcje te łączy jeden wspólny sposób przetwarzania pierwotnego sygnału diagnostycznego - wykorzystują one metodę FAM-C. Metoda ta bazuje na naturalnym przetwarzaniu wahań prędkości obrotowej poszczególnych ogniw kinematycznych zespołu napędowego przez prądnicę pokładową na modulacje częstotliwości. Metoda dzięki swym szczególnym właściwościom jest wyjątkowo korzystna dla cyfrowego automatycznego przetwarzania diagnostycznego. Tester może być przyłączony w dowolnym, dogodnym dla obsługi miejscu sieci elektroenergetycznej, z daleka od niebezpiecznych stref statku powietrznego.

11

Selected problems of transmission wear of the Mi-24 helicopter

Gębura A., Zientalski K.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2015

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nr 37

25--44

EN

The hypothesis of mutual, destructive impact of the worn upper bearing of the WR-24 transmission on the Mi-24 helicopter's gearbox was stated. The Mi-24 is the only helicopter operated in Poland, in which the gearbox is mounted outside the main transmission – in the centre of the transmission shaft, between the main gearbox and the tail rotor. Damage to the gears in the gearbox of power generators is equivalent to termination of the tail rotor's drive. Such a termination immediately causes rotation of the body in the direction opposite to the direction of rotation of the main rotor. It is associated with the loss of lift and steering. It may lead to a disaster. Such an incident occurred in January 2011 in Afghanistan – both authors participated in its investigation. The authors, taking into account very good, almost legendary combat properties of the Mi-24, and their research of the specifics of wear and tear of the transmission elements, they think that, first, funds for development and implementation of the drive unit monitoring system should be made available specially for this helicopter. For this purpose, the authors propose to use the FAM-C method. It is characterised with significant ergonomics. Thank to this, multiple kinematic pairs can be observed simultaneously, and, therefore, the relationships between them as well.

12

Selected aspects of wear affecting keyed joints and spline connections during operation of aircrafts

Gębura A., Szymczak J.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2014

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nr 35

85—103

EN

The paper deals with selected deficiencies of spline connections, such as angular or parallel misalignment (eccentricity) and excessive play. It is emphasized how important these deficiencies are for smooth operation of the entire driving units. The aim of the study is to provide a kind of a reference list with such deficiencies with visual symptoms of wear, specification of mechanical measurements for mating surfaces, mathematical description of waveforms for dynamic variability of motion in such connections and visualizations of the connection behaviour acquired with the use of the FAM-C and FDM-A. Attention is paid to hazards to flight safety when excessively worn spline connections are operated for long periods of time.

13

Investigation of tribologic processes in bearing nodes with the use of the FAM-C and FDM-A methods – the model with elevated passive resistance

Gębura A.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

|

2014

|

nr 35

115—125

EN

The paper discloses selected results of application of the FAM-C (a.c. generator) and FDM-A (d.c. generator) methods for comprehensive troubleshooting of bearing nodes in single-spool turbojet engines. A.c. generators provide information about slow-changing processes and, consequently, that information makes it possible to monitor radial and axial clearance of bearings as well as misalignment of shafts. On the other hand, the information transmitted by d.c. generators refers to fast-changing processes and is suitable to monitor dynamic properties of antifriction bearings: variations in the Q factor of bearings, slip factor of mating antifriction surfaces, rates of bearing cage rotation against its journal, etc. Nearly ten years of observations and data collection from a numerous set of engines during their operation have made it possible to classify processes associated with wear of bearings and categorize them into four phenomenological models. This paper is devoted to the model of elevated passive resistance.

14

Comparison of two analytical calculations of harmonic analysis of the current drawn by the voltage-source active rectifier from the electrical grid

Kus V., Josefova T.

Prace Instytutu Elektrotechniki

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2013

|

Z. 263

79--93

EN

Voltage-source active rectifier eliminates characteristics harmonics, which are drawn by diode (thyristor) rectifiers from the electrical grid. The paper shows analytical analysis of the current drawn from the grid by voltage-source active rectifier. The first part presents the principle of the voltage-source active rectifier. The next part describes both analyses of the current and the last part shows comparison of both analyses with simulations.

PL

Prostownik aktywny eliminuje charakterystyczne harmoniczne prądu, które są pobierane z sieci elektroenergetycznej przez prostowniki diodowe (tyrystorowe). Artykuł przedstawia analityczną analizę prądu pobieranego z sieci elektroenergetycznej przez prostownik aktywny, stanowiący źródło napięcia. Pierwsza część omawia zasady działania prostownika aktywnego jako źródła napięcia. Następna część opisuje analizy prądu przeprowadzone dwoma sposobami, a kolejny fragment przedstawia porównanie wyników tych analiz z wynikami badań symulacyjnych.

15

Distance measurement errors in silent FM-CW sonar with matched filtering

Marszal J., Salamon R.

Metrology and Measurement Systems

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2012

|

Vol. 19, nr 2

321-332

EN

The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signals with reduced power and significantly prolonged repeat time. The application of matched filtration in the sonar receiver provides optimal conditions for detection against the background of white noise and reverberation, and a very good resolution of distance measurements of motionless targets. The article shows that target movement causes large range measurement errors when linear and hyperbolic frequency modulations are used. The formulas for the calculation of these errors are given. It is shown that for signals with linear frequency modulation the range resolution and detection conditions deteriorate. The use of hyperbolic frequency modulation largely eliminates these adverse effects.

16

Diagnosing of electro-mechanical converters by using a method of frequency modulation analysis

Gębura A., Tokarski T.

Journal of Polish CIMAC

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2012

|

Vol. 7, no 2

31-43

EN

This paper describes methods for the diagnosing of aircraft electro-mechanical converters, used by the Aircraft Equipment Laboratory , Avionics Division , Polish Air Force Technical Institute ( PAFTI). Each of them has been discussed on the basis of systematized, available theoretical knowledge verified by using results of the authors’ laboratory research. Especially is exposed the diagnostic method , elaborated by these authors and implemented under their supervision, based on measuring and analyzing the parameters of one of the components of the direct current pulsations. The method is called FAM-C ( where FM stands for frequency modulation , A – alternating current, C – the method’s development level). Also, a related method based on measuring and analyzing one of the components of DC pulsations , is presented. It is called FDM-A (where FM stands for frequency modulation, D – direct current, A – the method’s development level ). Results of laboratory tests are also attached. Possible using the converter groove pulsations during rotor’s rundown phase after external feeding the excitation winding, has been also discussed – in this case DC motor turns into DC generator. This makes it possible to apply the FDM-A method. As DC generator usually shows a few times greater resolving power, it is possible to monitor mechanical elements which generate higher frequencies. To highlight the problem, have been discussed effects of physical phenomena which influence the forming of output voltage pulsation component of DC generators.

17

Generator z modulacją częstotliwości jako źródło sygnału testującego dla toru pomiarowego z częstotliwościowym nośnikiem informacji

Warda P.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 8

235-238

PL

W pracy przedstawiono wybrane problemy w stosowaniu generatora z modulacją częstotliwości do badania toru z częstotliwościowym nośnikiem informacji. Zaproponowano warunki które powinien spełnić sygnał generatora w celu zminimalizowania wpływu niedokładności generowanego przebiegu na wyniki badań. Przedstawiono wyniki dla przykładowego modelu toru.

EN

The paper presents select problems in using a generator with a frequency modulation in order to research on a slotted line with a frequency data carrier. Necessary conditions for the testing signal obtained from the generator which allow minimising its influence on research results are proposed. Results obtained for a model of slotted line are shown.

18

The monitoring of the bearing joints with excessive axial clearances using the FAM-C AND FDM-A methods

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2010

|

nr 27

121-136

EN

The intended aim of the paper is to discuss issues resulting from the observation of thee bearing support elements/components in single-shaft turbine engines with excessive axial clearances. Described are parameters and symptoms of such a condition, probable hazards, as well as capabilities of determining it with the FDM-A1 and FAM-C2 methods. Presented are hypotheses formulated by the Authors on subsequent stages of the wearout of bearing support elements/components in an aircraft turbojet engine, which lead to that excessive axial clearances start to arise. Theory of the issue has been completed with results of diagnostic examination of engines and data from the mechanical inspection of the engines after their disassembly.

19

The monitoring of the bearing nodes with excessive radial clearances using the FAM-C and FDM-A methods

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2009

|

nr 25

109-127

EN

The paper has been intended to present findings resulting from the monitoring of the bear-ing support elements with increased radial clearances with the FAM-C1 and FDM-A2 meth-ods. The role the lubricant film plays in this type of the rolling-elements' wear has been described. Discussed are symptoms, parameters, and hazards to the resonant state in bearing nodes, as well as capabilities of diagnosing them with the FAM-C and FDM-A methods. Hypotheses about subsequent stages of the wearing process in aircraft turbojet engine's bearing support assemblies, including how the resonant state occurs, have been presented. The mechanism of the resonance in rolling-element bearings has been de-scribed, with particular attention paid to the effects of gyrostatic moments upon the bearing support elements, both in micro- and macro-scale. Theoretical analyses have been sup-plemented with findings resulting from the diagnostic work carried out by the Authors, and with data from the mechanical verification of engines in the course of the authorised dis-mantling thereof.

20

The diagnosis of onboard generators (alternators)

Gębura A., Radoń T.

Polish Maritime Research

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2009

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nr 3

36-40

EN

In the paper selected problems related to diagnostics of onboard generators and alternators fitted with control systems are discussed. Problems refer to commutator generators and synchronous single- and threephase alternators. Special attention is paid to commutation effects. Results of incorrectness and possibility to detect them are discussed. There are also discussed effects associated with changes in a character of pulsation, which occur during shortings or insulation clearances in rotor or stator wiring. Possibility of diagnosis of generator’s or alternator’s parts by means of analysis of pulsation component parameters is indicated. In the case of alternators a number of diagnostic methods based on observation of changes in shape of voltage or frequency modulation, is discussed. This allows to detect many mechanical or electrical faults of generators, alternators or their control systems.