Implementation of adaptive feedforward cancellation algorithms for pre-embossed rigid magnetic (PERM) disks

Pre-embossed rigid magnetic (PERM) disks provide the potential to improve storage capacity, simplify the manufacturing process, and reduce overall manufacturing costs. Since the tracks including servo sectors are pre-embossed and assembled into the drive, there is runout mainly due to the inherent eccentricity. In order to compensate repeatable runout, an adaptive feedforward cancellation (AFC) scheme is implemented. It is shown through experiments that the AFC is effective in selectively canceling the desired frequency. Cancellation of the first three harmonic components is demonstrated, and experimental results are presented. Without track following servo, the AFC is able to reduce the position error signal (PES) by 83% of the track pitch.