Patent ID: 8853905

Claim:
A radial direction controller that is applied to a magnetic bearing apparatus that supports a rotating body to be levitated by at least an electromagnet, comprising: a radial control circuit that controls the displacement of the axis of the rotating body in the radial direction; a negative bearing stiffness elimination circuit that is connected in parallel with the radial control circuit, and that outputs a signal related to negative bearing stiffness; a current value command device that outputs a current value for controlling the electromagnet, on the basis of a signal outputted by the radial control circuit and the signal related to the negative bearing stiffness outputted by the negative bearing stiffness elimination circuit; a DC component extraction device that extracts a DC component from the current value outputted by the current value command device; a correction coefficient calculation device that calculates a correction coefficient on the basis of the DC component extracted by the DC component extraction device and a bias current for the electromagnet; and a coefficient multiplication device that multiplies the signal outputted by the negative bearing stiffness elimination circuit by the correction coefficient calculated by the correction coefficient calculation device.