Model based fault identification: the LS fitting approach in the frequency domain.
Several different faults can be modelled as equivalent forcing systems.
The rotor system can be modelled in different ways:
  • Supporting structure as 1 dof mass-spring-damper.
  • Supporting structure as "dynamic stiffness".
  • Supporting structure as "modal" model.
Two different fault identification procedures can be used:
  • Traditional "displacement method" uses complete model of the system and the measured displacements in the bearings.
  • A innovative "force method" uses the model of the rotor alone, and the "measured" bearing forces. These forces can also be calculated with the model of the oil film bearing and with the measured shaft-bearing displacements.
The advantages are the following:
  • The supporting structure can be neglected.
  • Errors in the supporting structure model do not influence the result.
  • The non-linearity of the oil film can be taken into consideration.