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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Sat, 20 May 2006 13:13:07 GMT
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Original-From:
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steve <sjbaker1@airmailNOMORESPAM.net>
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Viewed:
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2456 times
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John Barnes wrote:
> Pulses emitted by "the other sensor" can arrive at just the wrong moment,
> creating a false range reading. Clever numerical filtering can eliminate this
> kind of thing under certain circumstances - for example you may be following
> parallel to a wall and obtaining a series of readings which should be all within
> a likely range. If you suddenly receive a reading which is outside the expected
> range, you might discard it. In otherwords, if you maintain an average and only
> accept readings within a certain range of that average as bona fide, then you
> may be able to guard against this kind of interference to a certain extent.
A better alternative would be to develop protocols in which the NXT
controllers use their communications to tell each other what they are
about to do. If you can sent a message that says "I'm about to do an
ultrasound 'ping' - so you'd better ignore any readings you are about
to get and refrain from doing a 'ping' of your own." then do a range
measurement and finally send another message "Thanks - I'm done with
the ultrasound system for a while."...then the systems can arrange to
avoid interfering with each other.
After all, robots move slowly - you are unlikely to need high speed
readings.
I guess it all assumes that you have software control of the ultrasound
sensor so that you can control when it sends a ping and make it shut
down between pings.
For competitive NXT events, it might be worthwhile for this group to
come up with a standard protocol that contest organisers could
require everyone's entries to adhere to if they wish to use the
sonar system.
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Message has 1 Reply:
 | | Re: Ultrasonic sensor interactions
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| (...) This is a great idea except for one very important item: there is no such thing as a broadcast message (ie: a message sent to everyone) using Bluetooth. So for any such system to work, each robot has to know about every other robot, and send (...) (18 years ago, 21-May-06, to lugnet.robotics)
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Message is in Reply To:
| | Re: Ultrasonic sensor interactions
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| (...) In a word, multiple ultrasonic sensors can be a problem. This is a general problem and not specific to Lego ultrasonic sensors. Pulses emitted by "the other sensor" can arrive at just the wrong moment, creating a false range reading. Clever (...) (18 years ago, 19-May-06, to lugnet.robotics)
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