Subject:
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Re: an idea, can someone tell me if this is possible/been done before/etc?
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 2 Dec 2003 21:06:50 GMT
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Original-From:
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Jim Choate <ravage@einstein^IHateSpam^.ssz.com>
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Viewed:
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1362 times
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On Tue, 2 Dec 2003, Kevin L. Clague wrote:
> What if we assume that each output drives a motor,
Bad assumption but it would work, the RCX is too limited on I/O to be
doing that sort of stuff except in the case of simple rollers/walker.
Since legs have symmetry it's silly not to take advantage of it here,
you've got to use it to keep the thing in some sort of static/dynamic
balance. If you're going to use differential/planetary/co-axial/pullies/etc.
then -use- them [1].
Basic engineering efficiency. My approach is Occham's Razor and the
concept of 'elegence'. If there is -anything- that isn't demonstrably a
requirement for the goal(s) then it's 'outta here!'.
With regard to the discussion of walkers and leg blockage. Let's assume
for a moment that instead of using switches or something we decide to do
something mechanical. For example a triangular cam attached to the end of
the leg segment. It would allow the end of the leg, assuming sufficiently
low compliance [2], to move up over an object due to the rotational
translation of forces the cam would provide. It takes the horizontal
energy and transforms it into vertical energy.
You can also move the cam farther up the leg, say a gear with a pin
sticking out of it. It would normaly be positioned such that the pin was
at the bottom of the rotation at all times during normal operation.
However, when the leg stalled the extra torque would be sufficient to trip
some sort of 'switch' (eg a rubber band providing counter tension) once
the torque got over a specific amount. The rotation of the gear would move
the pin to the top, thus providing a tad extra leg clearance for the bot.
It would need a bang/bang stop at this point just to make sure nothing got
too torqued out of shape if the leg is still blocked.
[1] It reminds me of an article SciAm many years ago about using pullies
and springs to do basic addition/subtraction/and/or/not. Pretty
powerful, don't know if it's universal as in UTM.
-- --
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James Choate 512-451-7087 ravage@ssz.com jchoate@open-forge.com
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