Abstract: In field balance, if only the unbalance can be identified there’s no need to identify the bearing coefficient, so a new method, based on without the bearing parameter identification, is proposed to identify unbalance of nonlinear rotor system. In the new method, those forces related to the bearing parameters are all ascribed to the oil film force. The oil film force is nonlinear, but it is closed to periodic force. So it can be expanded by Fourier transform. According to the characteristic of unbalance response the identification equations of power-frequency vibration can be acquired. In this algorithm the power-frequency vibration is caused by unbalance and oil film force, but it can be separated by different location matrix of the two kinds of forces. Based on holospectrum and correlation, the power-frequency signal can be extracted from measured vibration. Then, the unbalance can be identified by solving the equations. In order to test this new algorithm the power-frequency vibration amplitudes before and after balancing are compared through a lot of numerical simulations. The simulations show that the new algorithm is effective, stable and robust. Finally, the method is validated by experiment.

Key words: Nonlinear rotor bearing system, Parameter identification, Unbalance