Intelligent Monitoring System Based on Noise-Assisted Multivariate Empirical Mode Decomposition Feature Extraction and Neural Networks

Table 4

Characteristic frequencies formulations.

Component	Characteristic frequency	Formulation
Fixed-axis gearbox	Meshing frequency
Planetary stage	Planet frequency [49]
	Carrier frequency [49]
	Meshing frequency [49]
Bearing	Ball pass frequency, outer race [50]
	Ball pass frequency, inner race [50]
	Fundamental train frequency (cage speed) [50]
	Ball (roller) spin frequency [50]