Serwis Informacyjny "Mechatronika"


tytuł: Acoustic signal processing and analysis for the byside monitoring station
kategoria: materiały konferencyjne
dział: inne

To improve safety in the rail transportation, permanent monitoring of technical state of critical parts and sets of rail vehicles is necessary. Interesting idea for the enhancement of present diagnostics systems, widely consider on the world, seems to be conception of use of byside monitoring station which aim, in the particular points of rail track, would be inspection of passing trains and identification and analysis of signals connected with safety of the railway traffic. Operation of the bysides monitoring systems bases on the assumption, that diagnostically interesting information is available in acoustic signal, which is emitted by the passing rail vehicle.
Grounded on this conception, paper presents possibility of acoustic signal analysis, which is generate by the moving vehicle and acquired by the stationary diagnostic station. Those circumstances introduce lot of difficulties in the fault - oriented signal analysis. Fundamental influence has Doppler effect, which causes in the observed signal, persistently change of the values of carrier frequencies. Paper presents the method of reduction of Doppler effect consequences, which definitely impede signal analysis and thwart use of conventional method of signal analysis. Presented method is a task - oriented signal dynamic resampling, which allows identification of undistracted frequencies and proceed further analysis and interpretation. The problem of diagnosis of real rail vehicle is more complicated, because we must proceed with not alone, but with many signals from the following wheels/carriers, which are situate close together and are moving with high velocity. For this purpose, simulation model of moving source signals was created. Using constructed model, many configuration of measurement station were tested, and the influence for the character of registered signal and selection of the proper technique of signal analysis, was exhibited. Application of proper selection measurement parameters creates opportunity to make use of Doppler effect or to minimize its influence. In the case of appropriate configuration of measurement station for the two different relevant distances of sources, it is possible to observe beat effect, which can directly deliver information about frequency variation produces by the Doppler effect. Discovering the character of disturbances, we are able to, for example, estimate the speed of moving vehicle. Further analysis of frequency and nature of beat effect can indicate the difference in the carrier frequencies of source signals (not connected to the Doppler effect), which give the information about differences in the kinematics and dynamics work of following vehicles sets, for example affected by the different wheel diameter. Spread of signal analysis supported by the model, makes possible appreciate the fact that signal acquisition performs with several microphones. Changing its arrangement and putting together signal during the object is closing and the signal during the object is recede, we are able creates sufficient condition for beat effect generation (even when the objects are moving in high velocity). Aiming better analysis and increase usefulness of beat effect attend of frequency shifting, which moves interesting frequencies to different band (better for analysis), is suitably. It also allows operate frequencies from particular sources in order to exhibit and identify beat effect, which might help to decide if the acquired information is connected to proper running of vehicle or there is some anomaly in its behavior. There is also chance to recognize the specific place, through the all carriages, where the anomaly was observed.
To perform described investigation, essential is the skill of signal identification, which modulates the amplitude of analyzing signal. Except classic methods, empirical mode decomposition was examinee.
The paper also includes the examples of described analysis in the application to the simulated data and to the real signals from the rail vehicles registered by the stationary measurement station.

rok wydania: 2008
wydawnictwo: Proceedings of International Conference on Noise and Vibration Engineering (ISMA2008), Leuven, Belgium, 15÷17.09.2008, vol. 1-8, pp. 2735÷2750, ISBN: 9789073802865
autorzy: J. Dybała, Sz. Gontarz, S. Radkowski


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