Newsgroups: comp.robotics
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From: shane@cs.sunysb.edu (Shane Bouslough)
Subject: Re: A sense of balance
Message-ID: <1993Jan31.211938.9674@sbcs.sunysb.edu>
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Date: Sun, 31 Jan 1993 21:19:38 GMT
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John Nagle (nagle@netcom.com) wrote:

: shane@cs.sunysb.edu (Shane Bouslough) writes:
: >Mark Epperson (epperson@adobe.com) wrote:
: >: What about a track-ball or joy-stick mounted upside down
: >: with a weight attached?
: >I would rather have something a little more robust. How about a set
: >of mercury switches around a sphere? 
: 
: These are all messy mechanically.

True.

: The best approach is a sealed cup of liquid with four capacitive sensing
: plates.  This gets you two axes of balance.

Sounds good so far...

: The choice of the liquid is tricky (you want a medium poise, no foaming,
: and uniform viscosity over the operating temperature range) but worth
: experimenting with.

Hmmm... getting more complicated...

: Etak, the vehicle navigation people, used to make these, packaged with a
: rate gyro, but I don't know if they still do.  They did considerable work
: to get the geometry and liquid characteristics right so that driving on
: rough roads wouldn't introduce excessive noise.  

Oops, I think you just blew my whole $$$ budget. This sounds a bit like
overkill for a little six-legged thing. I like the carpenter's level idea
more and more. If I can't find the actual device I heard about, I think
it wouldn't be so hard to measure how much of the bubble is present at
a certian location. Of course, they're only good over a few degrees, so
perhaps a few arranged in a shallow arc are necessary.

Now a bubble in a ring with photosensors around it would be perfect, and
you get 360 degree tracking to boot. I'll just make a quick run down to the
bubble-in-a-ring store and pick up a few.

: John Nagle

-Shane

--
Shane Bouslough       | #include <stddisc.h>
shane@sbcs.sunysb.edu | "Follow your bliss" - Joseph Campbell
