希尔伯特变换解调分析在故障诊断中应用的局限性研究

Limitation studies on application of Hilbert transform demodulation analysis in fault diagnosis

在机械设备，特别是具有齿轮、滚动轴承的机械设备故障诊断中，广泛使用解调方法分析诊断故障．目前使用的希尔伯特（Ｈｉｌｂｅｒｔ）变换解调方法，特别是宽带解调方法，不但对包含故障信息的时域相乘信号解出调制信号，而且对两时域相加信号，也以频率之差作为调制信号解出；当采用带通滤波来克服这种局限性．并用细化分析来提高解调分析的频率精度时，由于算法的影响会出现调制频率的高次谐波分发生频率混叠而反折到低频部分的混频现象．不论是哪一种情况都会在解调谱上出现引起误诊断或无法分析的频率成分．

Demodulation analysis is widely employed in fault diagnosis especially of machines with gearbox and bearing. Hilbert transform demodulation analysis with broadband demodulator in current use can demodulate modulated signals not only from timedomain multiplying signals with fault information, but also from time-domain addingsignals and display them as the difference of their frequency, which is one of the limitations to be overcome. However,when we try to overcome this limitation with the help ofthe band-pass filter and improve the frequency precision of demodulation analysis withthe help of zooming analysis, there occurs the phenomenon of frequency mixing at lowfrequency ranges, which is the reflection of frequency aliasing of higher harmonic components of the modulated frequency owing to algorithm. It is clear that no mailer whichmethod is employed, there will be wrong diagnosis or unanalysable frequency components on the demodualtion spectrum.