Patent ID: 7012778
Filing Date: 2006-03-14
Classification: G11B

Abstract:
1. In a magnetic head positioning method in which servo information containing a series of servo information numbers disposed along each of a plurality of tracks having a series of track numbers on a magnetic disk is read by a magnetic head, and said magnetic head for recording and reproducing information onto or from the magnetic disk revolving according to the servo information is positioned at a target position, an eccentricity control method for magnetic disk comprising: a phase learning step of learning a phase deviation amount representing the phase relation between a change in said servo information number read by said magnetic head and a change in the eccentricity amount of the magnetic disk; a step of detecting a positioning error signal of said magnetic head on the basis of said phase deviation amount; a step of generating a signal of sine wave in synchronization with the revolution frequency of the magnetic disk or of cosine wave having a phase difference of 90 degrees relative to said sine wave; a step of obtaining a weight coefficient from said signal of sine wave or cosine wave and said positioning error signal of the magnetic head; a step of obtaining an eccentricity compensation signal representing an eccentricity control amount by multiplying the signal of sine wave or cosine wave by said weight coefficient; and a step of controlling the magnetic head by using said eccentricity compensation signal, and thereby compensating the eccentricity of the magnetic disk.