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From: jn163051@longs.LANCE.ColoState.Edu (Joel Nevison)
Newsgroups: comp.robotics,comp.lsi,sci.electronics
Subject: Re: velocity sensing for robotic joints
Keywords: LVDT
Message-ID: <8441@ccncsu.ColoState.EDU>
Date: 13 Aug 90 15:34:08 GMT
References: <1990Aug7.205751.21206@ecf.utoronto.ca> <19481@well.sf.ca.us> <140483@sun.Eng.Sun.COM>
Sender: news@ccncsu.ColoState.EDU
Reply-To: jn163051@longs.LANCE.ColoState.Edu (Joel Nevison)
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Organization: Colorado State University, Fort Collins, CO  80523
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In article <140483@sun.Eng.Sun.COM> cmcmanis@stpeter.Eng.Sun.COM (Chuck McManis) writes:
>
>Another area you might consider is using simple inductors. A system
>which has as much resolution as you'd care to spend on it. The 
>tecnique being to place an inductor on one section of the joint and
>a moving "core" (in the form of a conductive wire) on the other 
>section. Energizing the inductor and then measuring the emf generated
>in the core. Note I've never actually implemented one of these so
>I don't have complete confidence in its viability but I don't see
>any obvious flaws in it.

My first contribution, neat group!

I have seen this implemented on a GCA stepper as velocity feedback to 
prevent the auto-focus from oscillating.  They called it an LVTD which
I believe stands for linear velocity difference transducer? Correct me
someone.   I don't believe the coil was energized, I think they had a 
magnet moving inside.  This was measuring some fairly small velocities
as the total travel was less than 1/2" and I never saw it move that distance
faster than ~1/3 second (in failure mode).   Normally it measured moves
on the order of a millimeter.

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| Substitution mass confusion   /           Joel Nevison                  |
|    Clouds inside my head     /  jn163051@longs.lance.colostate.edu      |
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