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HDA Configuration for Minimum Idle Mode Power by Optimum Read/Write Head Positioning

IP.com Disclosure Number: IPCOM000104849D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 138K

Publishing Venue

IBM

Related People

Dang, HP: AUTHOR [+3]

Abstract

In present disk drives the Read/Write heads are positioned at the outer diameter (OD) during idle mode. Detailed power and drag analysis shows that in disk drives with a small form factor, the power consumption is significantly affected by the position of the heads due to the drag created at the head-disk-interface (HDI) bearing surface. Hence a minimum power idle mode is achieved by positioning the heads closer to the inner diameter (ID) of the disk.

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This is the abbreviated version, containing approximately 52% of the total text.

HDA Configuration for Minimum Idle Mode Power by Optimum Read/Write Head Positioning

      In present disk drives the Read/Write heads are positioned at
the outer diameter (OD) during idle mode.  Detailed power and drag
analysis shows that in disk drives with a small form factor, the
power consumption is significantly affected by the position of the
heads due to the drag created at the head-disk-interface (HDI)
bearing surface.  Hence a minimum power idle mode is achieved by
positioning the heads closer to the inner diameter (ID) of the disk.

      The total power P into a spindle motor controller that is
designed to drive a spindle motor at a nominal speed of N RPM with a
disk of diameter D and a head at radius r can be generally
represented as a nonlinear function:

  P =  alpha (N, D, r)  D sup p N sup m r sup n ','
where  alpha (N, D, r)  is a parameter that is defined by HDA
geometry, motor loss functions, head skew angle, fly height, etc.
The exponents p and m are traditionally considered to be of values
greater than 1, and hence much focus was given to study their
effects.  No attention was given to study the effect of head position
"r" and its significance (i.e., n = ?) on the total spindle motor
power.  The idea for the proposed idle state configuration is based
on minimizing the effect of  r sup n .

      A spindle motor of a 2-disk 2.5" form factor disk drive was
spun at the design speed with various levels of component
integration.  The input current to the controller was measured under
the following conditions:
a).  With no-disks (D=0),
b).  With a single 2.5" disk and no head (r=0),
c).  With a single disk and a single head at various positions on the
disk.

      The average power into the driver was computed, and the
corresponding load torque due to various components was estimated.
Fig. (1a) shows the average current at various test conditions.  By
means of the motor torque constant, and by direct measurement of
slider drag at 3600 RPM, the bar chart shown in Fig. (1b) was
generated.  The torque estimates of ferro fluid (FF) seal, bearing
etc. were obtained from manufacturers.  As evident from Fig. 1, the
contribution of slider position to load torque is significant
compared to all other individual contributions.  This finding
motivated further expe...