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Use of One Line Torque Feedback in Automated Screwdriving Process

IP.com Disclosure Number: IPCOM000122252D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Malek, SS: AUTHOR [+4]

Abstract

For any automated screwdriving process to be successful it must either guarantee to never jam a screw, never break a screw and always torque the screw to the proper torque, or it must be able to sense when these events occur. In this article we propose a sensing scheme capable of determining screw jamming, screw failure and final torque value.

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Use of One Line Torque Feedback in Automated Screwdriving Process

      For any automated screwdriving process to be successful
it must either guarantee to never jam a screw, never break a screw
and always torque the screw to the proper torque, or it must be able
to sense when these events occur.  In this article we propose a
sensing scheme capable of determining screw jamming, screw failure
and final torque value.

      The sensor is a torque-sensing device mounted on the
screwdriver and is capable of measuring the amount of torque applied
to the screw.  Figs. 1, 2 and 3 show the layout of the torque-sensing
device mounted to a standard electric screwdriver.  The screwdriver
is mounted to a free-spinning bearing.  A force cell is anchored to
ground, a known distance away, and a lever arm connects the two.  For
small rotations the force measured on the force cell is proportional
to the amount of torque applied to the screw by a factor equivalent
to the length of the lever arm.

      This torque-sensing device can be used in a number of ways.  It
can be used to characterize the torque curves for a specific
application.  A trace of the external torque-measuring device set to
a peak hold state and a trace of the output from the screwdriving
torque sensor can be made.  The peak torque values are very close,
thereby supporting the correlation results.  Also, from the traces
there is some amount of recoil from the driver.  The traces
illustrate two things...