A method of identifying runout of an active magnetic bearing at standstill and low speed is presented. The on-line current bias injection method found in literature is improved, but is still found to converge too slowly for sinusoidal tracking. A new method which approximates the deviation from the magnetic centre using a disturbance force observer is presented and tested on an experimental fly-wheel AMB system. The new on-line method is fast enough for real-time tracking of the magnetic centre deviation. The estimated angle derived from the pseudo-magnetic centre was successfully utilized for start-up of the drive’s sensorless vector control.
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