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Repeatable Runout Compensation at Servowrite

IP.com Disclosure Number: IPCOM000105227D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 26K

Publishing Venue

IBM

Related People

Mason, RK: AUTHOR

Abstract

The disclosed method compensates for repeatable runout (RRO) effects incidental to the spindle motor operation of a head disk assembly (HDA). Due to the design of an HDA spindle motor, significant repeatable mechanical runout is written into each servo track during servowrite. This RRO generally has detrimental effects on performance.

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Repeatable Runout Compensation at Servowrite

      The disclosed method compensates for repeatable runout (RRO)
effects incidental to the spindle motor operation of a head disk
assembly (HDA).  Due to the design of an HDA spindle motor,
significant repeatable mechanical runout is written into each servo
track during servowrite.  This RRO generally has detrimental effects
on performance.

      If the servowrite actuator is situated at 180 degree
relationship with respect to the product actuator during servowrite,
even harmonic RRO (2,4,6,8, etc.) is maximum as read by the product
actuator.

      The performance impact of such RRO is minimized or or
eliminated by placing the servowrite actuator at a 160 degree
relationship with respect to the product actuator.  The result of
this alternate placement is cancellation of the written 8th harmonic
RRO by the spindle mechanical motion.  Thus, RRO is invisible to the
product actuator, and the HDA to perform as though RRO were
nonexistent.

Disclosed Anonymously.