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 17:31:14 GMT
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Original-From:
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Duncan Colvin <Duncan@climax.co!stopspammers!.uk>
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Viewed:
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565 times
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How easy would it be to build a satellite dish style set up, where the beam
is reflected to a sensor in the middle of the dish? Has anyone done this
already? Are there prebuilt dishes that could be used? Is there an
affordable solution?
DBC
<Two thumbs fresh>
> -----Original Message-----
> From: Sattler Chris-QA1406 [mailto:Christopher.Sattler@motorola.com]
> Sent: 08 August 2000 18:23
> To: lego-robotics@crynwr.com
> Subject: RE: Autonomous Robot
>
>
> 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 1 Reply:
 | | RE: Autonomous Robot
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| (...) Try a flashlight reflector. Rat Shack used to sell a 'cigarette lighter' that was a hyperbolic dish to light from the suns rays. ___...___ He is able who thinks he is able. Buddha The Armadillo Group ,::////;::-. James Choate Austin, Tx (...) (24 years ago, 8-Aug-00, to lugnet.robotics)
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