Newsgroups: comp.robotics
Path: utzoo!utgpu!watserv1!watmath!mwtilden
From: mwtilden@watmath.waterloo.edu (M.W.Tilden, Hardware)
Subject: Re: Memory Metals
Message-ID: <1990Nov9.191747.7239@watmath.waterloo.edu>
Organization: University of Waterloo
References: <0093F732.C4DCDA20@EA.USL.EDU>
Date: Fri, 9 Nov 90 19:17:47 GMT
Lines: 40

In article <0093F732.C4DCDA20@EA.USL.EDU> leecemb@EA.USL.EDU writes:
>Has anyone ever used or heard of someone who has used memory metals in robots.  

It's called nitenol wire and it comes in several different strengths
and deformation abilities.  There was a company in New Jersey that sold
devices and raw materials using nitenol but they folded about a year
ago.

Why?  Well, I bought their experimenters sample pack and found out that
the metal has very poor use-stability.  You can reform the metal if you 
put current through it (ie: heat it up) but too much current actually destroys
the memory latice.  This wouldn't be so bad but the wire has this property
of changing it's resistance based on the amount of stress it's under.
High stress areas wind up losing their memory because current builds
there in comparison to other low stress, low resistance locations along the
wire.  Result: useslessness.  What's the point of making a robot which 
cannot handle variable loads wthout destroying it's own muscles?

The University of Oxford built the most complex nitenol arm so far
but quickly grew frustrated with it because of it's slowness and 
need for continual re-calibration.  Kyocera in Japan had a
demonstration of small robots using nitenol wire at a trade
show two years ago but conceeded that the stuff needed vast improvements
before any serious robotics could be considered.

For myself, I had hoped to use the stuff for walking-creature legs
but aside from the above, the stuff is also grossely inefficient, 
so any such creature would not even be capable of lifting it's processor,
let alone it's batteries.

Anyway, it was a good idea at the time.  Maybe will be again.

Is all.


-- 
Mark Tilden: _-_-_-__--__--_      /(glitch!)  M.F.C.F Hardware Design Lab.
-_-___       |              \  /\/            U of Waterloo. Ont. Can, N2L-3G1
     |__-_-_-|               \/               (519) - 885 - 1211 ext.2454,
"MY OPINIONS, YOU HEAR!? MINE! MINE! MINE! MINE! MINE! AH HAHAHAHAHAHAHAHAHA!!"