Abstract
A technique in measuring torsional vibration signal based on an optical encoder and a discrete wavelet transform is proposed for the extraction of gear meshing characteristics. The method measures the rotation angles of the input and output shafts of a gear pair by using two optical encoders and obtains the time interval sequences of the two shafts. By spline interpolation, the time interval sequences based on uniform angle sampling can be converted into angle interval sequences on the basis of uniform time sampling. The curve of the relative displacement of the gear pair on the meshing line (initial torsional vibration signal) can then be obtained by comparing the rotation angles of the input and output shafts at the interpolated time series. The initial torsional vibration signal is often disturbed by noise. Therefore, a discrete wavelet transform is used to decompose the signal at certain scales; the torsional vibration signal of the gear can then be obtained after filtering. The proposed method was verified by simulation and experimentation, and the results showed that the method could successfully obtain the torsional vibration signal of the gear at a high frequency. The waveforms of the torsional vibration could reflect the meshing characteristics of the teeth. These findings could provide a basis for fault diagnosis of gears.
Highlights
Torsional vibration, which is the rotational vibration induced by torque fluctuation of rotary parts, is commonly observed in all kinds of rotating machinery
The small difference in frequency indicates that the remaining detail signal is the torsional vibration signal of the gear, verifying the feasibility of the proposed method for extracting the torsional vibration signal of gears at a high frequency
A convenient and effective measurement method of torsional vibration signal based on an optical encoder and a discrete wavelet transform is proposed for the extraction of gear meshing characteristics
Summary
Torsional vibration, which is the rotational vibration induced by torque fluctuation of rotary parts, is commonly observed in all kinds of rotating machinery. The measurement and monitoring of torsional vibration is significant for the safety of the rotary system. Numerous studies about using the torsional vibration signal for the fault diagnosis have been published. Fan [1] extracted the torsional vibration signal from the measured signal using time-averaging method and detected the eccentricity of test gears. Feng [4] presented explicit equations to model torsional vibration signals, considering both distributed gear faults and local gear faults, and validated experimentally the signal models and the effectiveness of joint amplitude and frequency demodulation analysis in extracting planetary gearbox fault symptoms. Fundamental to the experimental study of rotary machinery characteristics and fault diagnosis is the accurate measurement and extraction of the torsional vibration signals
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