A novel health index is proposed to detect incipient fault of ball bearing and monitor its progression earlier than the visible fault appearance using the microphone sensor. Frequency energy shift method is employed to extract the health index (HI), based on the findings that the energy is concentrated and shifted in specific frequency bands as the fault progresses. In the early stage, the anomaly of incipient fault is detected by the Chi-square test of HI. The end of life where visible faults appear is defined by the moment when the raw signal and its envelope spectrum at fault frequencies show distinct increase. Natural faults made by run-to-fail (RTF) experiments are used to demonstrate the approach. The performance of HI using the microphone sensor is superior to that of vibration due to the advantage of non-contact sensing. It successfully indicates early fault detection and damage progression before the visible faults show up.
- Acoustic sensor
- Anomaly detection
- Frequency energy shifting method (FESM)
- Natural fault
- Run-to-fail (RTF)