1996 Volume 32 Issue 7 Pages 1043-1050
A self-sensing magnetic suspension system was studied both theoretically and experimentally. It used a switching power amplifier whose switching times were controlled by a current comparator with some hysteresis. An analysis and several experiments on the amplifier showed that its switching frequency changed linearly with the gap between the electromagnet and the suspended object. They demonstrated that switching signal could be treated as the output of a displacement sensor of frequency type. Phase-locked loop and frequency-feedback control were applied to stabilize the magnetic suspension system. In experiments, frequency-to-voltage (F/V) converters were used to realize the frequency-feedback control. Feeding back the F/V converted switching signal lead to stable suspension. When a phase-locked loop (PLL) control was activated in addition to the frequency-feedback control, the suspension system was pulled in lock. The accuracy of floating was improved by the PLL.
