Browse Prior Art Database

Closed Loop Breakaway Through a Magnetic Latch

IP.com Disclosure Number: IPCOM000118848D
Original Publication Date: 1997-Aug-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 36K

Publishing Venue

IBM

Related People

Ho, P: AUTHOR [+4]

Abstract

After spinning up a disk drive that utilizes a magnetic latch to prevent the actuator from moving over the data area of a disk, the actuator must break free from this latch before data can be accessed. Typically, this is done with a fixed set of pulses to the driver controlling the actuator motion. This is known as open loop control because there is no feedback to the controller. This invention utilizes position information written in the parking area to perform a closed loop breakaway through the latch. This presents a method for more controlled breakaways and to prevent damage to both the heads and disks, which may occur during uncontrolled breakaways.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Closed Loop Breakaway Through a Magnetic Latch

      After spinning up a disk drive that utilizes a magnetic latch
to prevent the actuator from moving over the data area of a disk,
the actuator must break free from this latch before data can be
accessed.  Typically, this is done with a fixed set of pulses to the
driver controlling the actuator motion.  This is known as open loop
control because there is no feedback to the controller.  This
invention utilizes position information written in the parking area
to perform a closed loop breakaway through the latch.  This presents
a method for  more controlled breakaways and to prevent damage to
both the heads and  disks, which may occur during uncontrolled
breakaways.

      There is a small area between the magnetic latch and the crash
stop where there is room for the actuator to move.  The described
solution for breaking out of the latch is based on writing a pattern
in this area which can be used in a closed loop manner.

      Once the drive is up to speed, the actuator is moved around
inside the latch using open loop control until good servo pattern is
found.  The loop is then closed and the servo track follows on this
pattern.  Under closed loop control, the actuator is then positioned
in the latch such that there is some space between it and the latch
(this space is used to build up speed to break through the latch).
Remaining under closed loop control, a seek is then initiated to a
target track outsid...