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Coarse Actuator Home Position Drive and Detection

IP.com Disclosure Number: IPCOM000106186D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Chow, WW: AUTHOR [+2]

Abstract

In the bring-up of the actuators for an optical file, the coarse actuator has to move to a home position without reliable feedback. The coarse actuator has to overcome a lot of forces and offsets while moving at a slow speed towards fixed rubber stops. This disclosure shows a method to get good velocity stability without feedback. The design also gives a positive indication that the actuator is in contact with the rubber stop without additional sensors.

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This is the abbreviated version, containing approximately 90% of the total text.

Coarse Actuator Home Position Drive and Detection

      In the bring-up of the actuators for an optical file, the
coarse actuator has to move to a home position without reliable
feedback.  The coarse actuator has to overcome a lot of forces and
offsets while moving at a slow speed towards fixed rubber stops.
This disclosure shows a method to get good velocity stability without
feedback.  The design also gives a positive indication that the
actuator is in contact with the rubber stop without additional
sensors.

      There are three operations that are multiplexed on the tow
leads of the coarse actuator coils:  (a) open-loop voltage drive, (b)
dynamic braking by shorting the two ends, and (c) back EMF detection.
By changing the percentage of time for the three modes of operations,
a variety of performances can be achieved.  If the coarse actuator
has two independently controlled coils, the three operations can be
designated for separate coils.  Dynamic braking helps to stabilize
the speed because the amount of braking is proportional to the speed
of the actuator.

      In a system design for lwo cost, the compination of open-loop
drive and dynamic braking is sufficient to give good performance.

      Back EMF detection can be used to change the duty cycle between
the driving and braking.  Back EMF provides the system with voltages
that is proportional to the speed and direction of the motion.  The
dynamics of the system is drastically different befo...