Repeatable runout compensation for disk drives using multi-loop adaptive feedforward cancellation

Presents a multi-loop adaptive feedforward cancellation (AFC) in order to compensate for the repeatable runout (RRO) in disk file systems such as a disk eccentricity not only in the track following mode but also in the seek mode. By using a double-loop AFC, a cancellation of the fundamental RRO component with fixed coefficients is applied in the seek mode, resulting in a stable settling characteristic which is independent of the disk eccentricity. In the track following mode, the first four harmonic components of the RRO are cancelled so that each harmonic component of a position error is reduced to less than 0.01 μm_0-p