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From: dseltzer@draper.com (Don Seltzer)
Subject: Re: Definition center of compliance?
Message-ID: <dseltzer-180494133621@dss1368.draper.com>
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References: <2oa08b$6j2@bigguy.eng.ufl.edu>
Date: Mon, 18 Apr 1994 18:36:20 GMT
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In article <2oa08b$6j2@bigguy.eng.ufl.edu>, eric@joker.mil.ufl.edu (Eric M.
Schwartz) wrote:

> Can anyone send me a good standard definition for center of
> compliance?
> 
> Thanks,
> Eric
> eric@mil.ufl.edu

If a force is applied to a compliant structure, the structure will tend to
both deflect laterally and also rotate about a point which is the center of
compliance. If the force is applied in line with this center of compliance,
the structure will only deflect laterally without rotating.

Why is this important in robotics? If a robot is inserting one object into
another (peg in hole problem), the center of compliance for the
peg-gripper-robot system is usually located near the gripper. If the tip of
the "peg" touches the side of the hole, it will deflect both laterally and
rotationally. The rotational deflection will usually cause the peg to jam
in the hole.

There is a wrist-mounted device called a Remote Center Compliance (RCC)
which can "project" the center of compliance out to the tip of the "peg".
Contact with the side of the hole causes sideways deflection, but no
angular misalignment, allowing insertion to proceed smoothly. RCC's, which
were invented in the 1970's by S. Drake, S. Simunovic, and P. Watson of
Draper Laboratory, are often used on commercial assembly robots.

Don Seltzer  dseltzer@draper.com
Draper Laboratory
Cambridge, MA
