Abstract: Weight factors corresponding to plural areas into which a disk is concentrically divided, respectively, are previously stored, and an amount of eccentricity control is calculated using the previously-stored weight factors during settling operation. Further, when an impact larger than a predetermined value is applied, calculation of weight factors is stopped. Thereby, the seek time can be shortened, and positioning of the head can be stabilized.

Abstract: Weight factors corresponding to plural areas into which a disk is concentrically divided, respectively, are previously stored, and an amount of eccentricity control is calculated using the previously-stored weight factors during settling operation. Further, when an impact larger than a predetermined value is applied, calculation of weight factors is stopped. Thereby, the seek time can be shortened, and positioning of the head can be stabilized.

Abstract: 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.

Abstract: 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.

Abstract: A single device, of which structural size is minimized, allows it to provide a method of driving a spindle motor, a spindle motor driving circuit, a method of driving a magnetic disk, and a magnetic disk device, each for driving a spindle motor in an optimal driving mode or with optimal driving characteristics according to a command from a higher level system or a type of an application in use. According to the command from the higher level system, a driving mode switching unit in a spindle motor driving circuit switches driving of the spindle motor between a pulse-width modulation driving mode by a pulse-width modulation driving means and a linear driving mode by a linear driving means. Thus, a single spindle motor driving circuit can provide driving in a driving mode suitable for an intended use.