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Cylinder ID Decoding for Defective PES Burst

IP.com Disclosure Number: IPCOM000123149D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 69K

Publishing Venue

IBM

Related People

Ueda, T: AUTHOR [+3]

Abstract

Disclosed is a Position Error Signal (PES) decoding method which is used as a position information by actuator servo. This method can avoid wrong cylinder number adjustment in case PES pattern has a defect. During track following condition, disable function of cylinder adjustment is added to micro code or hardware.

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Cylinder ID Decoding for Defective PES Burst

   Disclosed is a Position Error Signal (PES) decoding method
which is used as a position information by actuator servo.  This
method can avoid wrong cylinder number adjustment in case PES
pattern has a defect.  During track following condition, disable
function of cylinder adjustment is added to micro code or hardware.

   Fig.1 shows an example of track format of which servo has
4 PES burst patterns.  If head is positioned around the track
boundary, sometimes the adjacent cylinder ID (gray code) is read.  In
this case, the real position is adjusted +/-1 by MPES and SPES values
which are calculated by the amplitude of PES burst patterns.  Head
position which is used by servo can be calculated by the MPES, SPES
and the cylinder ID.

MPES and SPES are calculated by following equations.
           A - B
   MPES = -------
           A + B
           C - D
   SPES = -------
           C + D
  (A, B, C and D: Amplitude of PES burst A, B, C and D)

   Fig. 2 shows the relation between head position and MPES,
SPES.  In Fig. 1, the part (1), (2), (3) and (4) show the same head
positions as Fig. 2.  Generally 1 track is 256 PES.  MPES becomes 128
(=80h) at each track center.  SPES becomes 128 (=80h) at each track
boundary.  In Fig.1, MPES and SPES take following values at each head
position.
  Head Position   Cylinder ID   MPES and SPES value
  -------------   -----------  ...