Newsgroups: comp.robotics
Path: brunix!cat.cis.Brown.EDU!agate!spool.mu.edu!umn.edu!gold!roger034
From: roger034@gold.tc.umn.edu (Brynn Rogers)
Subject: Re: PROPOSAL: A robotic Butterlfy!
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References: <1994Jul29.103802.22064@msuvx2.memphis.edu> <31cecd$rel@search01.news.aol.com> <1994Jul30.125109.22128@msuvx2.memphis.edu>
Date: Mon, 1 Aug 1994 02:54:49 GMT
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In article <1994Jul30.125109.22128@msuvx2.memphis.edu>,
Mark C. Langston <umlangston@cc.memphis.edu> wrote:

  [stuff deleted]
>
>Well, after reading posts both in favor and opposed to the project, here's
>what I've decided:
>
>Voltage is no problem.  I have right here some silver oxide watch batteries
>that measure about 5-6cm in diameter, amd about 2cm in hieght, and output
>1.5v. I could readily install several in a body and still have a lightwieght
>power souce.  Amperage on the other hand will be a problem.  Too much so
>to make muscle wires practical.  Therefore, I reconsidered, and decided 
>upon some form of solenoid to move the wings (faster, less current needed).
>Basically the same idea as a relay switch, but using the switch itself
>to move the wings...e.g., power up one electromagnet, wing goes up...
>turn it off and power up the other, wing goes down.  Should be able to
>get one strong and small enough to make it feasible.
>

Mark, a solenoid is also a power hungry device.  I designed a paper/plastic
tape cutter (2 inch wide) that we use in our label printing machines.
We charge up a 6800uf cap to 60 volts, then drop it into a solenoid that
has a 1/2 inch stroke.  Current peaks at 18 Amps for a few milliseconds,
and by about 30 ms the entire charge on the cap is gone.  This gives a
nice and violent snap on the solenoid which closes a scissors.
  You wouldn't need anything that big, but we found that a solenoid is 
about 1/2 as efficient as an electric motor in turning energy into work.
(measured results comparing a motor to the solenoid setup, and the solenoid
was probably doing more work than the motor)  The solenoid cutter has half
as many parts and is faster and more reliable, so we went with the solenoid.
  Few small solenoids can pull even a one inch stroke.  Solenoids are also
heavy.

  I like the idea of using CO2 or some other energy source that packs
a lot of power.   I also think if the entire wing was made up of solar cells
you would have lots of power (and not to heavy).


Brynn

--
Brynn Rogers     roger034@gold.tc.umn.edu

