Newsgroups: comp.robotics
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From: seeker@indirect.com (Stan Eker)
Subject: Re: Ultra-sonic ranging
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Date: Sun, 22 Jan 1995 01:28:33 GMT
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Kent Gibbs (kmgibbs@ix.netcom.com) wrote:
: 	Does anyone have any thoughts about the feasibility of measuring 
: the strength of the returning echo rather than time of flight in a 
: ranging system?	I realize that the return signal is very weak and would 
: have to be fed through an op-amp or similar amplifier and input into an 
: A/D converter. I'm just trying to get some thoughts from all of you 
: about the possible pro's and con's of doing this. Has any work been done 
: on this?

Sure has.  The strength of the return echo relates to what it bounced off
of, primarily, and (very) secondarily to the distance.  It's useless if your
robot thinks the couch is 20 feet farther away just because it's made of
fabric and foam rubber instead of steel.

The *time* of the return echo is a very good distance indicator, since the
speed of sound in air doesn't change very much over temp and pressure,
unless you're in the middle of a hurricane.  If you are, but away your rug
robot and head for shelter.

