Patent ID: 7061710
Filing Date: 2006-06-13
Classification: G11B

Abstract:
1. A head positioning system, comprising: a positioning unit that positions a head in a target position on a disk medium that has a plurality of servo sectors containing servo data that is written to read from the disk medium, and the disk medium is rotating; a unit that senses a position error (PES) of the head relative to the target position; a controller that outputs an amount of control operation of the positioning unit based on the position error in a feedback control system; a repeatable run-out (RRO) measuring unit that measures an RRO residual component from the input value of the controller; a linear filter operating unit that is associated with the inverse function of the sensitivity function of a feedback control system, the sensitivity function being a transfer function 1/(1+G), where G is an open-loop transfer function of the feedback control system, and computes correction values from the measurement results of the RRO measuring unit; and a feed forward input generating unit which outputs a correction value (FF) for each of the servo sectors, wherein a result of addition of the position error (PES) and the correction value (FF) from the feed forward input generating unit is regarded as an input value of the controller, the RRO measuring unit has memories that are equal in number to the servo sectors and measures an RRO residual component from the input value of the controller, and the measurement is given by the following equation: where k is the number of a servo sector, RRO(k) is a result of measurement of RRO corresponding to the servo sector k, which is stored in a memory of the RRO measuring unit, PES(t) is a position error (PES) including distortion of the servo data, FF(k) is a correction value output from the feed forward input generating unit and corresponding to the servo sector k, and G is a gain constant of 0 through 1.