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Spindle Track Mis-Registration Minimization by Constructive Mass-Unbalancing of Actuator

IP.com Disclosure Number: IPCOM000111980D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Sri-Jayantha, M: AUTHOR [+4]

Abstract

External vibration contributes to Track Mis-Registration (TMR) through three major components: 1) Actuator Imbalance, 2) Spindle Radial/Pitch Compliance, and 3) Head-Disk-Assembly (HDA) Rotation. The low end files are mounted directly to the vibration tester in which component (3) is minimum or null. At high Tracks-Per-Inch (TPI) the spindle radial compliance (2) is critical to TMR budget which can not be eliminated by a simple design change, particularly in the emerging oil-bearing systems. By intentionally mass UNBALANCING the actuator an effective "mechanical feed-forward" is produced in phase with spindle compliance-based TMR component in order to cancel it. The corresponding design change is easily achieved and implemented.

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Spindle Track Mis-Registration Minimization by Constructive Mass-Unbalancing
of Actuator

      External vibration contributes to Track Mis-Registration (TMR)
through three major components: 1) Actuator Imbalance, 2) Spindle
Radial/Pitch Compliance, and 3) Head-Disk-Assembly (HDA) Rotation.
The low end files are mounted directly to the vibration tester in
which component (3) is minimum or null.  At high Tracks-Per-Inch
(TPI) the spindle radial compliance (2) is critical to TMR budget
which can not be eliminated by a simple design change, particularly
in the emerging oil-bearing systems.  By intentionally mass
UNBALANCING the actuator an effective "mechanical feed-forward" is
produced in phase with spindle compliance-based TMR component in
order to cancel it.  The corresponding design change is easily
achieved and implemented.

      For high TPI DASDs the mechanical TMR contribution due to
external vibration is expected to be significant.  Among three major
sources of vibration-TMR components the actuator imbalance component
can be theoretically minimized through mass balancing.  HDA rotation
component can either be avoided (by direct mounting) or be minimized
by decoupling shock isolator design.  Radial component due to spindle
compliance can not be minimized given the realistic spindle design
constraints.  With the emergence of oil-bearing technology for future
HDA design, a significant radial TMR component may result, thus
limiting the vibration induced TMR performance characteristics.

      Fig. 1 schematically shows the effect of track displacement and
head movement when the HDA is subject to an acceler...