Detection of distributed gear faults with a new bispectral analysis

A new bispectral signal processing method is proposed to study abnormal gear vibrations due to distributed gear faults that are commonly found in many industries. This new signal processing method examines the phase relationships of prominent vibration frequencies of gears. In particular, this method can determine if the sideband frequencies generated from amplitude modulation are directly resulted from the quadratic phase coupling (QPC) between the tooth-meshing frequency and other gear faults related frequency. Based on the models of two distributed gear faults, shaft unbalance and gear eccentricity, a modified bispectral analysis method is developed. Simulation examples are provided to demonstrate the effectiveness. The results correctly match the model descriptions and therefore avoid the ambiguities in interpreting quadratic phase coupling that may exist if the conventional bispectrum is innocently applied