The Use of Wavelet Analysis for the Closed Loop Control of Vibration in Magnetic Bearing Systems

Wavelet analysis provides a method of identify-ing localised time-frequency components within a vibratory signal. It also has direct links with digital signal processing. This paper focuses on the use of wavelet analysis within ro-tor/active magnetic bearing systems for fault detection, system identification and closed loop transient control. The closed loop controller is formulated in the wavelet coefficient domain using real-time evaluation of the wavelet transform, which involves a signal processing delay. The controller is designed to mimimise the wavelet coefficients of measured rotor vibration signals. Hence, this implies that the rotor vibration will be attenuated by the control action. Experimental results are presented to show how control in the wavelet coefficient domain is effective in attenuating transient rotor vibration arising from step synchronous input forces.