Subject:
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RE: Autonomous Robot
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 8 Aug 2000 17:23:21 GMT
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Original-From:
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Sattler Chris-QA1406 <Christopher.Sattler@motorola.[antispam]com>
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Viewed:
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742 times
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I had a similar idea, but I was picturing a funnel-shaped mirror above a
light sensor so that no matter what angle you hit it at the light is
reflected down at the sensor.
-----Original Message-----
From: Ian Warfield [mailto:ipw47@hotmail.com]
Sent: Tuesday, August 08, 2000 8:59 AM
To: lego-robotics@crynwr.com
Subject: Re: Autonomous Robot
In lugnet.robotics, sjbaker1@airmail.net writes:
>
> Ian Warfield wrote:
> >
> > [...]
> >
> > Building off the base station idea mentioned earlier, set up a single • station
> > in the middle of the room/arena/whatever. This station incorporates an • extra
> > RCX, two motors, two rotation sensors, and two laser pointers, one mounted • on
> > the tower at ground level and one mounted about two feet high. The robot
> > itself sports a laser detection sensor.
> >
> > Here's the tricky part... use polar coordinates. Suppose the robot wants • to
> > know where it is relative to the tower. It stops, sends out an IR call • for
> > help, and enables its laser detection sensor. The base station receives • the
> > call, turns on the ground-level laser pointer, and starts rotating the • tower.
> > As soon as the robot detects the ground-level laser it signals again, and • the
> > tower stops rotating. Next the base station switches off the ground-level
> > laser and switches on the high-level laser. The high-level laser zeroes
> > itself perpendicular to the floor and starts sweeping upward towards
> > parallel. When the robot detects this laser, it signals again, and the
> > high-level laser stops.
> >
> > Now the base station records the orientation of the tower via the • turntable
> > rotation sensor and the angle of the high-level laser via the laser • rotation
> > sensor. The base RCX stores the turntable orientation which provides the
> > angle reference. It then multiplies the height of the tower (two feet in
> > this case) by the tangent of the angle of the tower-based laser to get the
> > distance from the base station to the robot. Finally, it sends the • ordered
> > coordinate pair to the robot, which updates its internal odometry and
> > continues on its way.
>
> Clever! ...Food for thought!
Thanks!
> The only snag I can see is that when the first laser is being acquired, • both
> the tower and the robot have to spin. It might take a LOT of rotations for
> them both to happen to be pointing in the right direction for an
> acquisition.
Not if you used an omnidirectional laser sensor. Picture, instead of only
one
face of paper, a paper cylinder. There would be a tube of paper mounted on
top of a circular LEGO piece (or *pieces* arranged in a circle) with a paper
top. All sides of the cylinder except from the bottom would be paper. Now
stick a light sensor vertically upward through the bottom of the cylinder.
Assuming the paper is diffuse enough, a laser striking anywhere on the paper
should make it grow brightly enough to be seen by the light sensor.
(Even better, if it's available - use a block of frosted or translucent
glass. This would transmit light even better than the paper would.
Wherever
the laser strikes the block, the whole thing would glow bright rose pink.
Stick it on top of a light sensor.)
> I suppose that once the tower knows where the robot is, it can do a little
> spiral search to re-aquire it when it gets lost - so it won't be necessary • to
> track the robot all the time. Knowing that would allow one tower to track
> MULTIPLE robots at once!
Cool.
> Thinking about precision - how accurate can you make a lego gear
> train/rotation sensor point? Seems to me like the slop in the gears would
> limit you to perhaps 1 degree precision.
Only if you hooked the rotation sensor directly to the motor. The slack
isn't
all that bad unless you use millions of gears. If you geared the turning
down
quickly enough (i.e. with the shortest gear train) you wouldn't have that
much
to worry about.
> Fine until the robot drives under the sofa!
:D
--Ian
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Message has 2 Replies:
 | | Re: Autonomous Robot
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| (...) Yes - but that wouldn't be a funnel shape - it would need to be a 'retro-reflector' that reflects all light back to it's source - no matter the direction. That's why I was babbling on about the retroreflective tape they have on kids clothes (...) (24 years ago, 9-Aug-00, to lugnet.robotics)
| | | Re: Autonomous Robot
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| in article Fz036w.F10@lugnet.com, Ian Warfield at ipw47@hotmail.com wrote on 8/8/00 6:08 PM: (...) Here's a picture of a marine radar reflector. (URL) back of a bicycle reflector is a hexagonal array of little triangular right-angle pyramids packed (...) (24 years ago, 9-Aug-00, to lugnet.robotics)
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