Newsgroups: comp.robotics
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From: nagle@netcom.com (John Nagle)
Subject: Re: A sense of balance
Message-ID: <1993Jan31.192458.24679@netcom.com>
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
References: <1993Jan31.085934.17072@adobe.com> <1993Jan31.161809.7936@sbcs.sunysb.edu>
Date: Sun, 31 Jan 1993 19:24:58 GMT
Lines: 18

shane@cs.sunysb.edu (Shane Bouslough) writes:
>Mark Epperson (epperson@adobe.com) wrote:
>: What about a track-ball or joy-stick mounted upside down
>: with a weight attached?
>I would rather have something a little more robust. How about a set
>of mercury switches around a sphere? 

       These are all messy mechanically.  The best approach is a sealed
cup of liquid with four capacitive sensing plates.  This gets you 
two axes of balance.  The choice of the liquid is tricky (you want a
medium poise, no foaming, and uniform viscosity over the operating 
temperature range) but worth experimenting with.  Etak, the vehicle
navigation people, used to make these, packaged with a rate gyro, but
I don't know if they still do.  They did considerable work to get the
geometry and liquid characteristics right so that driving on rough
roads wouldn't introduce excessive noise.  

					John Nagle
