Subject:
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Robot navigation - barcode stations?
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sat, 10 Mar 2001 10:45:33 GMT
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Viewed:
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1534 times
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Hi,
Some time ago, on this or another robotics list, someone was talking about
navigation and location sensing techniques for RCX based robots. After some
thinking, reading through the literature and messing with some homebrew
sensors I have one suggestion I`d like to put to the community - barcode
stations. This technique has been used in industrial robots I believe
(so it`s proabably among the swelling ranks of patented methods...) and
it is probably old news to the experts here (I`m relatively new to this
stuff..), but here is the concept behind a robot I am trying to build at
the moment. BTW, I have no idea if this will work, but I think it`ll make
for an interesting challenge.
Barcode stations are custom barcodes mounted between two LEDs, like
this (excuse the bad ascii art, you`ll need to cut&paste it into a text
editor with a fixed-width font to see it properly):
.----------------.
\|/| #| | | |#| | | |\|/
-O-| #| | | |#| | | |-O-
/|\| #| | | |#| | | |/|\
`----------------'
A differential light sensor is mounted on the robot at the same height
as the barcode station LEDs with the LDRs spaced so that they match the LED
spacing. A light sensor is mounted on a movable rack between the LDRs so
that it can scan the code when it gets close enough. Barcode stations are
placed around the area in which the robot moves in "kown" locations.
When a robot needs to fix its absolute position, it looks for the brightest
light source using the standard light sensor (so don`t try this in a
brightly light area, unless you use IR LEDs I suppose..). Once it has
chosen the brightest (and therefore closest) light source it moves towards
it, using the differential light sensor to make sure it is going in fairly
straight. Making sure the barcode lines up with the scanner could be
difficult (see below about this..) but once in place the scanner can read
the barcode to determine the station number, giving an accurate location.
Of course, there are some big problems here. The biggest (I think) is
matching the scanner with the bardcode. A possible solution is a barcode
station/linefollower hybrid where there robot follows lines with barcode
stations at strategic positions or off "junctions". Then there is the issue
of the barcode scanning itself - I may end up implementing something akin to
the barcode scanner at http://www.inchlab.com/barcode_scanner.htm but
mounting the laser and light sensor on the same movable rack rather than
moving the barcode. I haven`t tested how good the Lego lightsensor is for
this sort of task.
Anyway, comments, suggestions or constructive criticisms (except on the fact
that I am clearly insane for even trying this) are more than welcome.
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Message has 2 Replies:
 | | Re: Robot navigation - barcode stations?
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| (...) Actually, if you are trying this, be aware that LEDs are typically mounted on a panel that faces the user (more or less) and as such the rounded housing of most LEDs acts as a lens which projects most of the light out toward the user rather (...) (24 years ago, 11-Mar-01, to lugnet.robotics.rcx)
| | | Re: Robot navigation - barcode stations?
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| I think it's an excellent idea... I saw the barcode system being explained some years ago and I still think it can be the most accurate. One thing that's different in the system I saw was that there were no LED's used (not needed...) and it would (...) (24 years ago, 29-Mar-01, to lugnet.robotics.rcx)
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