Identification of Stiffness and Damping via SPHS Excitation and Multi-DOF Active Magnetic Bearing-Rotor Model

The equivalent stiffness and the equivalent damping are the important and commonly used parameters for representing the support characteristic of the Active Magnetic Bearing(AMB). A method for measuring the equivalent stiffness and the equivalent damping is proposed with parameter identification via the multi-frequency excitation. The parameter identification is based on the multi-degree of freedom(DOF) rotor model, not the single DOF model, which can not be suitably applied to the multi-DOF AMB-rotor system. Additionally, the Schroeder Phased Harmonic Sequences(SPHS) are applied to generate the signal for the multi-frequency excitation. SPHS can achieve the lowest peak value by means of appropriate selection for the relative phasing of each frequency component, so that the possibility of the rotor vibration exceeding clearances of AMB and the magnetic force reaching saturation is minimized. Finally, the experiments indicate that the proposed method can efficiently reduce the peak value for the superimposed multi-frequency excitation and correctly identify the equivalent stiffness and equivalent damping of the AMB-rotor system. Keywords: active magnetic bearing, multi-frequency excitation, Schroeder phased harmonic sequences, equivalent stiffness, equivalent damping