Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2005-08-30
2005-08-30
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06937424
ABSTRACT:
In one illustrative example, a method for use in reducing Repeatable Run Out (RRO) error in a data storage device involves obtaining an RRO measurement for each track of a limited number of N disk tracks; characterizing the RRO measurement for each track with real and imaginary values by performing a discrete Fourier transform (DFT) calculation on each RRO measurement; performing a least-squares fit on all of the real values to identify a first set of (n+1) coefficients of an nth-order polynomial function which is a function of disk track r and representable in the form Ai(r)=anrn+a(n−1)r(n−1)+ . . . +a1r+a0; and performing a least-squares fit on all of the imaginary values to identify a second set of (n+1) coefficients of an nth-order polynomial function which is a function of disk track r and representable in the form Bi(r)=bnrn+b(n−1)r(n−1)+ . . . +b1r+b0. RRO compensation is performed based on the relation DRRO(r, s)=Σi for all H{Ai(r)cos(i(s2π/total_sectors))+Bi(r)sin(i(s2π/total_sectors))} where DRROis the estimated RRO error; r is a track number; s is a sector number at track number r; i is an RRO harmonic number; H is a set of harmonics to be compensated; and total_sectors is a total number of sectors along track number r. Advantageously, RRO variations across the disk can be accurately compensated for with use of a small amount of memory.
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Chang Jen-Yuan
Raley Jay Francis
Hitachi Global Storage Technologies Netherlands N.V.
Hudspeth David
Oskorep, Esq. John J.
Wong K.
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