Development of magnetic bearing considering temperature drift on displacement sensor at low temperature

抄録

In this paper, the temperature compensation of an eddy-current displacement sensor using zero power control is confirmed by experiments. In zero power control, the control current is set to zero for a constant disturbance by changing the bias force obtained from the permanent magnet by controlling the position of the levitating body. We use the local current feedback control in this experiment among several methods of zero power control. By using a model of zero power control using the transfer function, it was confirmed that constant or low-frequency disturbances to the displacement sensor can be cancelled out by zero power control. The experimental apparatus is a basic magnetic bearing that supports only one axis. The eddy-current displacement sensor used for magnetic levitation is cooled from room temperature to liquid nitrogen temperature. The temperature drift of the eddy-current sensor, the displacement, and the control current were measured in the experiment. The eddy-current sensor used for position detection in magnetic bearings was cooled from room temperature to liquid nitrogen temperature while the levitating body was levitated. The temperature drift of the eddy-current sensor output was confirmed from the experimental results. Since the change in sensor output with temperature was very slow, the rotor was confirmed to levitate without any problems near the balanced position.