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 13:58:52 GMT
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Viewed:
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1363 times
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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 1 Reply:
 | | Re: Autonomous Robot
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| (...) both (...) for (...) one (...) on (...) paper (...) Now (...) paper (...) Wherever (...) I find Ian's proposal about the laser tower very clever. The only bad point about using an omnidirectional laser sensor on the robot is it can't get any (...) (25 years ago, 8-Aug-00, to lugnet.robotics)
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Message is in Reply To:
| | Re: Autonomous Robot
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| (...) Clever! ...Food for thought! 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 (...) (25 years ago, 8-Aug-00, to lugnet.robotics)
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