Health monitoring of ball bearings in a flywheel using amplitude modulation of ultrasonic waves

Ball Bearings are critical components in rotational machineries. Although various diagnostic methods have been proposed, most of them are based on passive methods utilizing the signals generated from rotating machineries themselves. Such passive methods usually require continuous measurement and have limited resolution on the damage in certain circumstances. In this paper, a new active diagnostic approach using amplitude modulation of the ultrasonic waves is proposed. By introducing this modulation, we are able to widen the frequency range of the signals. The ultrasonic waves are constantly emitted to the target ball bearing to pick up the damage signals. The signals generated from ball bearings that have strong correlations with the possible damage result in modulation of the carrier waves. Thus, change of signals such as amplitudes and frequencies associated with abnormality of ball bearing can be detected.