Time-Frequency Analysis of Acoustic and Vibration Data
| Autor: | Jia-Ming Huang, 黃嘉銘 |
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| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 The Fourier sine spectrum and Fourier sine spectrogram generators are employed to examine acoustic data of a remote control unmanned electrical helicopter, an Unmanned Aerial Vehicle (UAV) and vibration data of ball bearing. The transformation contains the following steps. For a given data string whose non-sinusoidal part have been removed, zero points around the two ends are identified by searching and interpolation. After dropping segments beyond two zero ends, the corresponding Fourier sine spectrum is obtained. The time-frequency transform imposes finite bandwidth Gaussian window upon the Fourier sine spectrum centered at a given frequency. The inverse Fourier transform of the band-pass limited spectrum gives the real part of the resulting spectrogram. Form the resulting spectrums much information concerning the dominate modes and corresponding harmonics can be captured. Moreover, the associated amplitude and frequency variations are partially reflected by the spectrum scattering around a mode. The detailed variations can be obtained by examining the spectrogram. This study separately examined the acoustic data of main rotor wing, tail rotor wing and holding by hand of the unmanned electrical helicopter. Many detailed information can be precisely extracted. For the UAV, the engine test information, the ground test information and take-off operation are examined. The result shows that the engine test facility is too rough. For the bearing test, defects of the inner race, rolling element and outer race are compared with the normal state. The resulting spectrum and spectrogram show much new information. These tests show that the spectrum and spectrogram have the potential to monitor the operating state of a complete system. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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