Servo track squeeze compensation in a disk drive
AssigneeWestern Digital Technologies, Inc.
InventorsJie Yu, Guoxiao Guo
Life of this patent
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Abstract
A disk drive that compensates for written-in track squeeze errors (TSEs) during track following is disclosed. The disk drive may be used to compensate for TSEs when determining the position error signal (PES) by implementing operations that include: determining a track squeeze value for a servo sector based upon read servo bursts; determining a PES value for the servo sector based upon read servo bursts; estimating a Squeeze Correction Coefficient (SCC) to account for track squeeze induced PES sensing gain variation associated with the servo sector based upon the PES value and the track squeeze value; calculating a squeeze corrected PES value based upon the SCC and the PES value; and utilizing the squeeze corrected PES value in servo control.
Claims16
A disk drive that compensates for servo track squeeze, the disk drive comprising:
- a disk having tracks, the tracks including a servo sector having servo bursts spaced sequentially around a circumference of the track for use in track following;
- a head to track-follow on the track, wherein track following includes the head reading the servo bursts;
- and
- a processor to compensate for track squeeze by implementing operations including:
- determining a track squeeze value for the servo sector based upon reading the servo bursts;
- determining a position error signal (PES) value for the servo sector based upon the read servo bursts;
- estimating a Squeeze Correction Coefficient (SCC) to account for PES sensing gain variation associated with the servo sector;
- calculating a squeeze corrected PES value based upon the SCC and the PES value, wherein the squeeze corrected PES value is calculated by an equation:
- Squeeze Corrected PES Value=SCC(z)*PES value(z), wherein z=position and SCC(z)=(|N|+|Q|)/(|N|nominal+|Q|nominal), where N and Q are burst measurements at position z;
- and
- utilizing the squeeze corrected PES value in servo control.
A method to compensate for servo track squeeze in a disk drive, the method comprising:
- reading servo bursts of a servo sector of a disk during track following;
- determining a track squeeze value for the servo sector based upon the read servo bursts;
- determining a position error signal (PES) value for the servo sector based upon the read servo bursts;
- estimating a Squeeze Correction Coefficient (SCC) to account for track squeeze induced PES sensing gain variation associated with the servo sector;
- calculating a squeeze corrected PES value based upon the SCC and the PES value, wherein the squeeze corrected PES value is calculated by an equation:
- Squeeze Corrected PES Value=SCC(z)*PES value(z), wherein z=position and SCC(z)=(|N|+|Q|)/(|N|nominal+|Q|nominal), where N and Q are burst measurements at position z;
- and
- utilizing the squeeze corrected PES value in servo control to compensate for track squeeze.
Dependencies are inferred from the claim text.