Realiziation of Phase-Locked and Frequency-Feedback Magnetic Bearings

Phase-locked and frequency-feedback loops are applied to stabilize an active magnetic bearing with displacement sensors of frequency type. In the phase locked loops, the control input is produced from the difference in phase between the reference and feedback signals. Since phase is the integration of frequency, integral feedback arises automatically. It leads to high-accuracy suspension. To speed up the process of phase-locking, a frequency-feedback loop is used in addition to the PLL loop. This loop can stabilize the system even without PLLs. Self-sensing suspension is realized with a switching power amplifier whose switching-time is controlled by a hysteresis comparator. Experiments demonstrate the feasibility of the phase-locked and frequency-feedback magnetic bearings of self-sensing type.