Patent ID: 7068451

Claim:
A disk drive comprising: (a) a disk comprising a plurality of tracks, wherein: each track comprises a plurality of data sectors and a plurality of servo sectors forming N servo wedges; and a wedge time period (WTP) occurs between each servo wedge; (b) a head actuated over the disk; and (c) a disk controller for estimating a sinusoidal error in the WTP due to eccentricity in the disk rotating by: (i) positioning the head over a selected one of the tracks; (ii) calculating an estimated WTP according to: EST_WTP=RTP+ â *cos(2 πk/N )+ {circumflex over (b)} *sin(2 πk/N ) wherein RTP is a reference time period corresponding to a nominal WTP, k is an index representing one of the servo wedges, and {â,{circumflex over (b)}} are adjustable coefficients; (iii) detecting an actual WTP by detecting an interval between the head passing over a first and second servo wedge; (iv) estimating a wedge time error e(k) as the difference between the estimated WTP and the detected actual WTP; (v) adjusting the coefficients {â,{circumflex over (b)}} for generating the estimated WTP according to: â ( k+ 1)= â ( k )− G*e ( k )*cos(2 πk/N ) {circumflex over (b)} (k+1)= {circumflex over (b)} ( k )− G*e ( k )*sin(2 πk/N ) wherein G is a predetermined gain; and (vi) repeating steps (ii)–(v) at least once.