Subject:
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Re: Ultrasonic sensor interactions
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 22 May 2006 05:06:27 GMT
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Original-From:
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Bruce Boyes <BBOYES@SYSTRONIX.avoidspamCOM>
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Viewed:
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2977 times
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At 06:22 PM 5/21/2006, steve wrote:
> Brian Davis wrote:
>
> > On a related note, I'm trying to see just how much interference
> > two US sensor
> > working in the same room actually produce. The result seems to be
> > "darn little",
> > but I need to test some more. This may not be as big a problem as
> > we're worried
> > about, I'm unsure now.
>
> Within the same room - is unlikely to be a problem - but think about two
> Sumo bots trying to find each other or two robots doing some kind of
> cooperative tasks in a contest or something...not likely to be so
> easy I think.
Agreed... perhaps surprisingly, based on dozens of hours of testing,
with 1) sumo bots with a ring of sonars on all sides 2) Lego bots
with two sonars on the front, we found no discernable problem. This
is an anecdotal report, but the first-order answer to the question
seems to be "it's nowhere near the problem you might expect", and
typically appears to be no problem at all.
Since we're working on a long term SonarMotion project here:
https://sonarmotion.dev.java.net/ we plan to do some more deliberate
testing with test equipment monitoring modules with deliberate
worst-case timing and placement.
In practice, other problems dominate: 1) reflecting at a low angle
causes the ping to not reflect back to the receiver at all, giving a
false max-distance reading, often just before you scrape up against
the object you were hoping to detect. 2) absorbent objects like
drapes or fuzzy fabrics don't give a strong echo. 3) highly spherical
objects don't have enough planar surface perpendicular to the sonar
module. 4) sonars with a narrow beam aren't as good close up as those
with wider or multi-lobed beams. For example, the Vex sonars won't
see my hand edge-on 20-30 cm away if it's located midway between two
modules offset by 15 degrees. But the Vex modules seem to have better
long distance performance, at 2 meters and up. The SRF04 modules on
the other hand have great detection up close, over a wide angle, and
are not so useful at distances in excess of a couple of meters.
That's our experience, anyway... we haven't used the new Lego sonars
- we are waiting for the NXT kits like a lot of other folks - but
expect them to be similar, assuming they are in the 40 KHz range with
similar beam patterns.
Regards
Bruce
If the human brain were so simple that we could understand it, we
would be so simple that we couldn't. - Emerson Pugh, 1977
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Message is in Reply To:
 | | Re: Ultrasonic sensor interactions
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| (...) Within the same room - is unlikely to be a problem - but think about two Sumo bots trying to find each other or two robots doing some kind of cooperative tasks in a contest or something...not likely to be so easy I think. (19 years ago, 22-May-06, to lugnet.robotics)
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