Active Online Monitoring for Main Shaft Slight Crack in Rotating Electric Drive System Based on Chirp Torque Injection

The fault of transmission main shaft often originates from cracks. Traditional condition monitoring for main shaft crack is often based on detecting the abnormal vibration and image caused by cracks, which cannot identify early slight shaft crack in time. In this paper, we use the inherent characteristic, resonant frequency of the main shaft, to monitor main shaft crack and propose an active condition monitoring scheme for monitoring the slight main shaft crack based on the chirp torque injection. First, we study the physical meaning of each order resonant frequency of the shaft system by a complex frequency domain-space shaft torsional vibration model, and determine the main shaft resonant frequency as monitoring indicator. Then, we obtain main shaft resonant frequency and monitor early slight cracks of the main shaft by chirp torque injection. Through theoretical derivation and experimental analysis, it is proved that our active monitoring scheme can be used to monitor early slight main shaft crack of the mechanical system in time to avoid the occurrence of severe faults.