Self-sensing Operations of Frequency-Feedback Magnetic Bearings

Two topics are treated in this paper for promoting industrial application of a self-sensing type of frequency-feedback magnetic bearing (FMB) which uses hysteresis aJllplifiers. First, a low-cost digital control system is developed in which the fi'equency of the switching signal of the aJTIplifier is converted to a digital form by counting hy a counter circuit. Thc converted signal is directly used for calculating control input for stabilization. Second, the incorporation of the observer-based self-sensing method to FMBs is discussed. It is shown that an observer estimating velocity and displacement can be constructed even in cUITentcontrolled magnetic bearing systems such as FMBs with hysteresis aJTIplifiers. The estimated signals are used to improve the dynarnic perfonnance of a self-sensing type of FMB.