Introduction to a Simply and Fast Algorithm for Variable Speed Bearing Diagnostics

In this paper a new algorithm for variable speed bearing diagnostics isproposed. The diagnostics of ball-bearing is used to be focused on constant speedapplications. In fact at constant speed bearing faults cause a vibration with particularcharacteristics that the analysis in the frequency domain reveals. The geometry of thebearing parts allows to find the correlation between faults frequencies and the rotationalfrequency of the shaft on which the bearing is mounted on. If the shaft moves with variablespeed or motion inversion, the instantaneous rotation frequency changes continuouslyand no fault characteristic frequency are available. Under the hypothesis that the shaftposition profile is known, this paper suggests to perform the diagnostics on variable speedapplications in two steps. In the first one both bearing geometry and the shaft positionprofile are used to make a simulated fault signal which is expected if a specific fault wouldbe present, while in the second step a comparison between the simulated signal and the realvibration signal is made in order to verify the presence of the fault in the bearing. Differenttest-studies are reported in order to validate the algorithm.