Detection and diagnosis of ball bearing imperfections in reaction wheels by micro-vibration test

The results of micro-vibration test contain information on unbalance level, torque ripples, and most importantly the bearing health status. In this paper, the envelop analysis technique is proposed for localizing imperfections in the bearing. The envelop analysis, which is a powerful method used in ball bearing fault diagnosis, is adapted to the micro-vibration data. This method analyzes the data around the structural resonance: through the amplification of the vibration smaller faults can be detected. The procedure of envelope analysis, its practical issues and robustness are validated with simulated signals. Finally, the envelope analysis is applied to diagnose and evaluate the change in bearing status throughout two environmental tests: sine vibration and full ECSS shock. The result of envelope analysis shows its high sensitivity in revealing the development of small imperfections, makes an initial step in reaction wheel condition monitoring (on-ground and in-flight) and provides insights in design improvement to further lower micro vibration levels of reaction wheels.