Browse Prior Art Database

Self-Move Servo Design Method

IP.com Disclosure Number: IPCOM000116565D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 114K

Publishing Venue

IBM

Related People

Ogasawara, K: AUTHOR [+3]

Abstract

In recent Hard Disk Drive (HDD) industry, the usage of Magneto Resistive (MR) head is one of the key breakthrough to achieve high performance and high recording density. The biggest challenge for MR application is to obtain the highly balanced sector servo system. However, the nonlinear responce of MR head to the offtrack direction makes servo system difficult to have good performance. This new scheme solved this nonlinearity and eliminated this inherent difficulties of servo system of MR head.

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Self-Move Servo Design Method

      In recent Hard Disk Drive (HDD) industry, the usage of Magneto
Resistive (MR) head is one of the key breakthrough to achieve high
performance and high recording density.  The biggest challenge for MR
application is to obtain the highly balanced sector servo system.
However, the nonlinear responce of MR head to the offtrack direction
makes servo system difficult to have good performance.  This new
scheme solved this nonlinearity and eliminated this inherent
difficulties of servo system of MR head.

By using this new method, transfer curve which relates PES and
physical displacement is obtained only using the functions which
usual drive have.  PES:  position error information and physical
displacement should be linearly related, but in actual, MR head has
nonlinear relation inherently (Fig. 1).  The degree of nonlinearity
varies from head to head.  As the result of this, servo system
contains unexpected error component in its calculatrion.  If this
transfer curve can be got for each head easily in the MFG test, many
applications to reduce the nonlinearity can be used adaptively.

This method consists of those three functions:
  1.  Head move without acceleration.
  2.  PES Dump during Head move
  3.  Calc. of Transfer Curve using dumped PES

The tracking part explains the each functions.
  1.  Head Move without Acceleration - This is one of the key scheme
in
       this new method.  The basic idea is to move the head slowly
       without big acceleration makes it possible to obtain the
transfer
       curve between PES and physical displacement.  In order to do
so:
   ...