Newsgroups: comp.robotics
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From: schuch@phx.mcd.mot.com (John Schuch)
Subject: Re: robot parts: info and question
Message-ID: <1993Feb2.162511.28716@phx.mcd.mot.com>
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Organization: Motorola Computer Group, Tempe, Az.
References: <1993Jan31.054717.2297@hpcvca.cv.hp.com>
Date: Tue, 2 Feb 1993 16:25:11 GMT
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In article <1993Jan31.054717.2297@hpcvca.cv.hp.com> abrown@hpcvcec.cv.hp.com (Allen Brown) writes:

>generally a limit switch.)  But if you are going to install an
>additional sensor, why not use a pot and measure position directly?

Potentiometers, unless they are of the very expensive variety, are
terribly accurate, the readings change with age, and are suseptable
to getting grunged-up by dirt and dust. I would avoid them.


>And I didn't like pneumatics because
>of the lack of control.  Basically all you get is bang-bang.

You are probably correct that pneumatics wouldn't be a good choice
for your application but for future reference, pneumatic systems
are not all of the bang-bang variety. There is a lot of work going
on in electro-pneumatic servo systems ( see Motion Control magazine,
January 1993 issue, page 10).
 

>Do you know of a better way to deliver force to the legs? 

How 'bout a linear actuator? I'm building a small one for a CD
robot project I'm working on. Find someone with satellite television
and look at the motor unit that swings the dish around. I'm building
a version of that assembly that 8 inches long, has a 6.5 inch
throw and it's crosssection is smaller than 1/2 inch by 1/2 inch.
It is very simular to your cable-pusher design.

John

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