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Adaptive Spindle Start Controller for Disk Files

IP.com Disclosure Number: IPCOM000101406D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

DeHillerin, CA: AUTHOR [+3]

Abstract

Disclosed is a method for starting up a direct-access storage device (DASD) spindle when one or more recording heads are sticking to a disk surface. This method determines the natural resonance frequency of the spindle, and generates an excitation signal for rocking the spindle at the same frequency.

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

Adaptive Spindle Start Controller for Disk Files

       Disclosed is a method for starting up a direct-access
storage device (DASD) spindle when one or more recording heads are
sticking to a disk surface.  This method determines the natural
resonance frequency of the spindle, and generates an excitation
signal for rocking the spindle at the same frequency.

      Conceptually the start routine consists of three main modes:
identification, excitation, and verification (Figs. 1a and 1b).  An
accelerometer is used to detect system characteristics (e.g., natural
rocking frequency) and a file microprocessor (usually idle during
power on) to generate the correct excitation signal (in frequency and
duration) for the stuck spindle.  Note that the resonance frequency
of the spindle is a function of the number of stuck heads.

      The sensor is a peizoelectric transducer mounted on an actuator
in such a way that it is most sensitive to suspension axial
deformation.  If operated in the right dynamic range, typically in a
100's Hz range, the transducer output is proportional to the
acceleration of a disk pack. It can be shown that the acceleration
profile tracks with good approximation to the displacement profile.

      Identification mode consists of an estimation of the resonant
frequency for the stuck spindle by counting the time between zero
crossings of the accelerometer (transducer) signal in response to
some disturbance.  The accelerometer output for free or step input
response to some initial displacement is a damped harmonic signal of
the same frequency as the displacement.  A high frequency clock is
used, and the average number of clock ticks N between successive zero
crossings is determined.  Disturbance must be large enough to ensure
that the heads that are not stuck move relative to the disks;
otherwise, static friction is not overcome for those heads, and the
system behaves as if all heads were stuck, g...