Browse Prior Art Database

Single Dual Purpose Shock Sensor and Actuator Latch for a Direct Access Storage Device

IP.com Disclosure Number: IPCOM000119167D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 6 page(s) / 156K

Publishing Venue

IBM

Related People

Khanna, VD: AUTHOR [+3]

Abstract

Disclosed is an active actuator latch for a Direct Access Storage Device (DASD) that is designed to keep the read/write heads at a specified location under high shock condition. This also functions as a shock detection device during the power-on operation of the drive. A Micro-VCM based design is presented wherein a moving-coil driven latch provides protection against non-operating shocks and a "compliantly" mounted magnet provides Back-EMF generation to assist in write inhibit during operating conditions. Each can be optimized separately for its purpose and so achieve the best-mode design. During the operating condition, the VCM is kept stationary against a hard stop by a preload.

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Single Dual Purpose Shock Sensor and Actuator Latch for a Direct
Access Storage Device

      Disclosed is an active actuator latch for a Direct Access
Storage Device (DASD) that is designed to keep the read/write heads
at a specified location under high shock condition.  This also
functions as  a shock detection device during the power-on operation
of the drive. A  Micro-VCM based design is presented wherein a
moving-coil driven latch  provides protection against non-operating
shocks and a "compliantly" mounted magnet provides Back-EMF
generation to assist in write inhibit  during operating conditions.
Each can be optimized separately for its  purpose and so achieve the
best-mode design.  During the operating condition, the VCM is kept
stationary against a hard stop by a preload.

      DASDs used in portable applications are potentially exposed to
high shocks and excessive vibrations.  During non-operating
conditions the hard drives are protected from large shocks by an
actuator latch that keeps the heads away from the data stored on the
disks. Typically,  a low cost device such as a passive inertial latch
is employed. During  operating conditions, however, the drives are
significantly more sensitive to shock/vibrations, so much so, that
most drives now employ  PZT-based sensors to detect low level shocks
/ excessive vibrations.  These sensors then generate a write inhibit
to prevent the heads from writing over data on adjacent tracks.  Both
the above functions are achieved at extra cost.  The challenge is to
minimize component cost without sacrificing the reliability.

      An active actuator latch, if properly designed, is considerably
more reliable than a passive latch in preventing the heads from
moving onto the data during a high shock event.  They can be designed
using an  electromechanical device or any other actuation technology
but are not  generally used due to their higher cost.  This device
tries to minimize  the cost and give the added reliability by
providing both the latching  and shock detection functions by the
same device.

      A specific configuration of the first part of this latch, i.e.,
the use of a Micro-VCM to provide latching is described in (1).  The
second part, which provides shock detection, is shown in Fig. 1,
where the general structure of the write inhibit function is given.
Observe that the back EMF is obtained from the Micro-VCM, but the
time rate of  change of flux, that couples into the coil, is achieved
by enabling the  air-gap magnets to move relative to the Micro-VCM
due to an external shock.  Fig. 2 shows in detail a magnet structure
that provides sensitivity to shock along X, Y and about Z axis
(angular).  The magnets  can be suspended using several methods.  The
simplest method would be to  introduce a thin layer of "soft"
visco-elastic material betwe...