A Meshing Modulation Method for Gearbox Weak Fault Feature Extraction

Identifying the addition in number and amplitude of side-band frequencies besides the meshing frequency or detecting the high-resonance frequency band stimulated by the localized fault and localizing the rotational frequency of the faulty gear in the corresponding demodulated spectrum are two nominated methods in the diagnostic of gear localized fault. However, it is difficult to identify these features if the corresponding localized fault is too weak to stimulate evident differences in sideband or resonance in the high-frequency zone. To address this issue, a new method which makes use of the excitation motivation with meshing frequency rather than the rotational frequency as the frequency to localize the gear weak fault frequency. The underlying mechanism of the proposed meshing modulation method is first: elaborated, and then an index called meshing modulated index is proposed and used to localize a particular modulated frequency zone in the raw spectrum, and the evident features of gear localized weak fault can be detected in the corresponding demodulated spectrum. An early pitting fault which is naturally generated on a gear life test bench is used to testify to the effectiveness of the proposed method.