Newsgroups: comp.robotics
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From: nagle@netcom.com (John Nagle)
Subject: Re: 3d input devices
Message-ID: <nagleDBKyvD.E90@netcom.com>
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References: <3tdlmf$hf7@npc.ece.utexas.edu><1995Jul6.102344.341@genrad.co.uk> <3thtci$m3n@pipe2.nyc.pipeline.com>
Date: Wed, 12 Jul 1995 01:59:36 GMT
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pernst@nyc.pipeline.com (Paul R. Ernst Jr.) writes:
>In comp.robotics hillsp@genrad.co.uk (Paul Hills) said: 
>>I've thought about this one before, and as an electronic engineer I came up  
>>with an electronics solution. My idea is to have four ultrasound
>>'stations' in  
>>a three-sided-pyramid (tetrahedron?) configuration. That is three stations
>>in a  
>>triangle at floor level, and one above the subject. The point on the
>>subject to  
>>be tracked would have a fifth station attached to it. 

      Ever see a Mattel PowerGlove?  It worked that way, although it
only had three fixed stations, so you didn't get any redundancy.  
It had two stations on the glove, so you got orientation as well as
position.  It's a reasonably good approach, although objects in the
workspace distort the results.  With four stations, accuracy improves.
Because errors due to obstructions are always in the direction of a 
too-long path length, resolving inconsistencies is straightforward.

					John Nagle
