| The rolling element bearing is one of the most important units in locomotive. Bearing failures would probably bring great suffering to railway transportation and safety. Therefore, the locomotive bearing vibration signal is analyzed by means of the Laplace wavelet and a novel fault diagnostic system for locomotive bearing was developed. The contributions and conclusions are made as follows:The characteristics of locomotive bearing vibration signal were discussed. It had been pointed out that the vibration signature of the damaged bearing consists of an exponentially decaying sinusoid having the bearing defect characteristic frequency. Since energy of the defect characteristic frequency is distributed at a very low level, it can be easily masked by noise. So it is difficult to distinguish the characteristic frequencies accurately using conventional single processing method.The waveform of the Laplace wavelet is single-sided damped exponential sinusoid, which is very similar to the impulse response waveform of the locomotive bearing. Using correlation-filtering method, the correlation coefficient between bearing signal and Laplace wavelet waveform was calculated and the similar signature was extracted. The simulated signal analysis showed that the bearing defect characteristic frequency could be extracted effectively by means of Laplace wavelet correlation filtering. Furthermore, the proposed method offers a means of reducing noise, the effect was better than the denoising method based on wavelet transform.A novel method for localized defect bearing detection was introduced. The time-domain vibration signals of rolling bearings with different fault conditions were filtered using Laplace-wavelet transform for correlation coefficient calculation. The correlation coefficient was processed by envelope spectrum and the bearing defect characteristic frequency was extracted. The effectiveness and practicability of the proposed methods was verified by the experiment of typical localized damaged bearings on a test rig.Based on the investigations mentioned above, a diagnostic system for locomotive bearings was developed. The system was successful applied to the bearings of the running gear of a locomotive. The effectiveness of proposed system was verified by locomotive test at standstill. |
