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In Situ Stiction Measurements during Radial Compress

IP.com Disclosure Number: IPCOM000110479D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Dhanota, GS: AUTHOR [+3]

Abstract

The circuit disclosed below attached to the VCM source current will monitor the back EMF across the coil by adding the series resistor R and the differential amplifier. When the heads are stuck to the disk, the current will induce no motion and the circuit will have a characteristic RL response. However, when the first head comes unstuck, there will be a redistribution of forces on the stick heads and slight carriage motion. This will show up as'back EMF and be a voltage spike at Vo. Thus, by knowing the current when the spike occurred and the force factor for the VCM, one may calculate the force for break away. This process continues, with the forces distributed in parallel across the remaining unstuck heads. This circuit can also be used to measure when an actuator latch is broken.

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In Situ Stiction Measurements during Radial Compress

      The circuit disclosed below attached to the VCM source current
will monitor the back EMF across the coil by adding the series
resistor R and the differential amplifier.  When the heads are stuck
to the disk, the current will induce no motion and the circuit will
have a characteristic RL response.  However, when the first head
comes unstuck, there will be a redistribution of forces on the stick
heads and slight carriage motion.  This will show up as'back EMF and
be a voltage spike at Vo.  Thus, by knowing the current when the
spike occurred and the force factor for the VCM, one may calculate
the force for break away.  This process continues, with the forces
distributed in parallel across the remaining unstuck heads.  This
circuit can also be used to measure when an actuator latch is broken.
For an actuator latch which restrains all motion, when the tip is
broken, then there is short (a couple of mm) unrestrained carriage
motion possible with little force required (assuming no stiction).
Thus, a step input from the current source will produce a step motion
with a broken latch, and no motion with a unbroken latch.  This is
easily monitored at Vo.

                            (Image Omitted)

      Disclosed anonymously.