Head control unit in a disk apparatus

摘要

A zone where a head is positioned is determined in a track to be one of zones 1 to 4 according to a combination of the polarities of phase-A and phase-B detection outputs having different phases, and the positional deviation of the head from the current position to the center of the target track is obtained from the phase-B detection output in the zone. The phase-B detection output is provided with a dead zone corresponding to a range where both detection outputs have a phase-difference error. Therefore, even if the phase difference has an error, the positional deviation of the head is accurately calculated.