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From: james@TWG.COM (James Marshall)
Newsgroups: sci.virtual-worlds
Subject: Re: Cheap Force Feedback for VR?
Message-ID: <13407@milton.u.washington.edu>
Date: 18 Dec 90 23:00:45 GMT
References: <12079@milton.u.washington.edu>
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Organization: The Wollongong Group, Palo Alto, CA
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More "HOW TO CREATE VIRTUAL PRESSURE" ideas:

Is there some kind of piezoelectric (?) material that rapidly
expands when a voltage is applied to it?  Some kind of foam,
in several layers if necessary?  It seems that such a material
would be ideal for the pressure pockets we are looking for.

Could such a material be created by applying the same voltage 
to all microscopic bits of the material, giving them the same
charge, thus causing them to repel each other?  (Well, it's a
theoretical start.)

If you want to try an air-pockets-and-tubes system, you might have
much better luck with a hydraulic, rather than pneumatic, system
(i.e. liquid rather than gas).  You have much better control over
exact pressures and quick pressure changes, especially if going
through any tubes that you want to be narrow.  Could be messy in
the alpha-testing, though. :-6

Even if you use a pneumatic or hydraulic system, you can reduce
the arm-borne load to wires instead of tubes, by doing the
following:  In each pressurized cell, have a small mechanical device
shaped like an accordian that can expand itself with a little power.
This would have the same effect as pumping more air or water into the
cell, but would require only electrical transmission.  Something like
a freely-floating diaphragm.  I actually think this approach would
be easier than it sounds, since the mechanics involved are pretty
simple.

Good luck to whoever makes this work, and especially who tests it
out first (visions of mangled hands dance in my head).

-James Marshall
 james@twg.com
 (e-mail is much surer to get a response than Net News)