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Improvement of Servo Pattern Accuracy for Sector Servo

IP.com Disclosure Number: IPCOM000113658D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 62K

Publishing Venue

IBM

Related People

Masuda, M: AUTHOR [+3]

Abstract

Disclosed is a method to improve servo pattern accuracy for sector servo in Hard Disk Drive (HDD). Usually Sector servo patern is written once on the disk during the manufacturing process and the dominant error of the servo pattern position comes from Non-Reapeatable-Run-Out of the spindle motor (NRRO).

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Improvement of Servo Pattern Accuracy for Sector Servo

      Disclosed is a method to improve servo pattern accuracy for
sector servo in Hard Disk Drive (HDD).  Usually Sector servo patern
is written once on the disk during the manufacturing process and the
dominant error of the servo pattern position comes from
Non-Reapeatable-Run-Out of the spindle motor (NRRO).

      Figs. 1 and 2 show the general idea of sector servo pattern
which has "A" and "B" pattern in Fig. 2.  Sector servo controls head
positioning using information of "A"and "B" pattern which are written
to be shifted half track.  When the readback signal of "A" and "B" is
equal the head is centered on track.  So the accuracy of "A" and "B"
patern are important to control head positioning.

      The NRRO causes the error of servo pattern which is average
offset in Fig. 3.  Because one track servo patern is written on one
cycle of the disk at the time of servo track write.

      The method of improvement for servo patern accuracy is as
follows.  If each bit of patern "A" and"B" could be independently
written on a different rotation of the disk as shown on Fig. 4, the
average offset of pattern "A" and "B" is dramatically improved.
Therefore servo write accuracy is improved.