Identification and optimization of unbalance parameters in rotor-bearing systems

Jianfei Yao*, Liang Liu, Fengyu Yang, Fabrizio Scarpa, Jinji Gao

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

41 Citations (Scopus)
390 Downloads (Pure)


The paper describes the identification and optimization of unbalance parameters in rotor-bearing systems. Two methods are proposed for the identification of the unbalance characteristics: the first is based on modal expansion combined with the use of optimization algorithms, while the second relates to the use of modal expansion technique applied to the inverse problem. In this work, the modal expansion technique is used to overcome the issue related to the use of a reduced number of measuring points. The equivalent unbalance forces can then be estimated by expanding the modal displacements into generalized coordinates of the equations of motion of the rotor system. An error due to the use of a modal expansion is however inevitable, and to solve the issue we propose the adoption of an inverse problem formulation to avoid the computation of the displacements at each measurement point. The axial location of the unbalance must be however known in advance, if the inverse problem approach is used to identify the unbalance parameters. We therefore propose in this work an integrated modal expansion/inverse problem methodology combined with an optimization procedure. The technique allows to identify the axial location of the unbalance, its magnitude and phase. Simulation and experimental investigations are carried out to verify the validity of the proposed methods in a double-disk rotor-bearing system. The results show that identification and optimization procedure for the integrated modal expansion/inverse problem approach provides more accurate predictions than the ones given by the pure modal expansion method.

Original languageEnglish
Pages (from-to)54-69
Number of pages16
JournalJournal of Sound and Vibration
Early online date14 Jun 2018
Publication statusPublished - 29 Sept 2018


  • Inverse problem
  • Modal expansion
  • Optimization
  • Rotor-bearing system
  • Unbalance identification


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