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Method for Positioning a Read/Write Head on a Desired Track

IP.com Disclosure Number: IPCOM000061322D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Kisaka, M: AUTHOR

Abstract

In the present method for positioning a read/write head on a desired track, a first correction operation is conducted by using a predetermined equation stored in a disk drive; if the first correction value is larger than a predetermined value a second correction operation is conducted by using a new equation. The read/write head can be positioned precisely onto the centerline of the desired track by up to two correction operations. As shown in Fig. 1, the read/write head reads servo data A and servo data B once per revolution which are written on either side of a desired track. The disk drive generates a PES (position error signal) A-B/A+B from servo data A and B. The PES is proportional to off track x from the desired track.

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Method for Positioning a Read/Write Head on a Desired Track

In the present method for positioning a read/write head on a desired track, a first correction operation is conducted by using a predetermined equation stored in a disk drive; if the first correction value is larger than a predetermined value a second correction operation is conducted by using a new equation. The read/write head can be positioned precisely onto the centerline of the desired track by up to two correction operations. As shown in Fig. 1, the read/write head reads servo data A and servo data B once per revolution which are written on either side of a desired track. The disk drive generates a PES (position error signal) A-B/A+B from servo data A and B. The PES is proportional to off track x from the desired track. However, the actual proportion of PES to off track is unknown to the disk drive since the actual proportion depends upon each track. Therefore, a first correction operation is conducted by using a predetermined proportion C stored in the disk drive. PES P0 is generated from the servo data A and B detected by the read/write head, and then a first off track x' is calculated by the equation x'=P0/C, as shown in Fig. 2. However, the first off track x' is different from the actual off track x0 because of the incorrect proportion C. If the x' is not large, the difference between x0 and x' is not large. Therefore, the read/write head can be positioned onto the centerline of the desired tra...