Patent ID: 6563663
Filing Date: 2003-05-13
Classification: G11B

Abstract:
A method for compensating for repeatable runout (RRO) errors in a disc drive having a servo loop for positioning a head relative to a track on a disc surface of a rotating disc, comprising:(a) retrieving a servo position value from the disc surface indication of head position relative to the track; (b) retrieving a compensation (ZAP) value from a table of ZAP values; and (c) compensating the servo position value with the ZAP value; (d) wherein the ZAP values are of the form: ZAP(k+1)=ZAP(k)+K&PHgr;(z)RRO(k), where K is a learning rate; k is iteration number &PHgr;(z) is a filter and RRO(k) is the repeatable runout error, and the following inequality is satisfied &rgr;(j&ohgr;)=|1âˆ’K&PHgr;(j&ohgr;)/(1+PC(j&ohgr;)|<1, where PC(j&ohgr;) is an open loop frequency response of the servo loop.