| 摘要 |
A problem to be solved is to calculate, at a high speed, a control amount for a magnetic head in an eccentricity control method for magnetic disk of a magnetic disk apparatus and thereby avoid the degradation of control performance due to control delay caused by a long calculation time. Another problem to be solved is to realize stable control performance even when a variation in the position error of the magnetic head relative to a target position is large, for example, in the seek and the settling of the magnetic head. In the start up of the magnetic disk apparatus, the phase relation between servo information numbers recorded on the magnetic disk 15 in advance and the eccentricity of the magnetic disk is learned. In the positioning of the magnetic head, a signal generated by multiplying, by a weight coefficient, a sine wave or a cosine wave the phase the revolution frequency of the magnetic disk is fed forward as an eccentricity control amount, whereby the eccentricity is compensated.
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