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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Thu, 10 Aug 2000 23:44:45 GMT
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Viewed:
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899 times
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in article BB60654DFAA8D311B16400508B6F2538580B34@il27exm05.cig.mot.com,
Sattler Chris-QA1406 at lego-robotics@crynwr.com wrote on 8/10/00 6:00 AM:
> Would a cylindrical mirror work as well as a retro-reflector? Once you hit
> it dead-on it would reflect back. It would reflect the laser beam to other
> parts of the room, but they would be limited to the horizontal plain in
> which the laser is already sweeping. The only problem would be if the
> cylinder was not vertical.
Not so good, I would think. The cylindrical surface spreads the beam out
and it gets quite a bit weaker and difficult to detect.
Haven't tried it, of course, so I'm guessing.
The first "communication satellite" was something called Echo, which was
essentially a big spherical Mylar balloon. If you aimed radio waves at it
they would bounce off and return to the Earth somewhere over the horizon.
Of course, this didn't work very well because spheres make pretty poor
mirrors for focusing! The radio waves scattered all over the sky and you
had to start with a pretty strong signal to get it sent where you wanted it
to go.
A cylindrical mirror isn't quite that bad, but the same principle applies.
>
> -----Original Message-----
> From: Steve Baker [mailto:sjbaker1@airmail.net]
> Sent: Wednesday, August 09, 2000 7:11 PM
> To: Sattler Chris-QA1406
> Subject: Re: Autonomous Robot
>
>
> Sattler Chris-QA1406 wrote:
> >
> > No' I don't think you correctly understood what I am proposing. The
> > reflective surface would be on the outside of the funnel shaped piece with
> > the narrow tip of the funnel resting on the center of the sensor.
> >
> > Funnel
> > \ / light beam
> > \ /______________
> > \ /|
> > ______V__
> > Sensor
> >
> > The light beam would have to arrive parallel to the sensor. If the outside
> > surface of the funnel/cone was at a 45 degree angle to the sensor the • sensor
> > would have to be as large around as the widest part of the cone and this
> > would determine how much the height of the beam above the sensor could • vary.
> > By curving the surface of the cone you could change this do some degree.
> >
> > Getting the light beam to arrive parallel to the sensor would be a problem
> > in and area of uneven terrain. I suppose you could use some kind of system
> > to keep the sensor horizontal.
>
> Right - but what I've been trying to say is that once you decide to have a
> 'tower' with lasers on it - and have it send data to the robot - you might
> as well but the light sensors on the tower too - which cuts down on the
> weight/power/RCX-outputs needed in the robot - which is "A Good Thing".
>
> Hence the interest in retroreflectors. If you can shine a laser from the
> tower and hit the retroreflector, the tower's light sensor (bolted right
> next
> to the laser and parallel to it) will get a strong return. If the tower
> laser
> misses the robot - then no reflection.
>
> So the software in the tower has to simply scan the laser around until it
> finds the robot - then track it (an easy problem to solve). The tower
> can tell the robot where it is in the world VERY easily. You could even
> put multiple towers around your home - and use them to track multiple
> robots in parallel.
>
> Once you get that right - all your robots know where they are all the time.
>
> If they need to know their heading, they can infer that from their
> consecutive
> positions relative to the tower when driving in a straight line - and use
> odometry when they go around corners or get into a position where their
> IR sensor cannot get the position data report from any nearby tower.
>
> This scheme would be *great* because you could install it permenantly
> in your home - and just thave all your robots use it. Robotic navigation
> then needs ZERO RCX inputs or outputs - and the software on the robot to
> read it is very non-intrusive.
--
Doug Weathers, http://www.rdrop.com/~dougw
Portland, Oregon, USA
Don't spam me - I know how to use http://www.spamcop.net
"On a clear disk you can seek forever"
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Message is in Reply To:
 | | RE: Autonomous Robot
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| Would a cylindrical mirror work as well as a retro-reflector? Once you hit it dead-on it would reflect back. It would reflect the laser beam to other parts of the room, but they would be limited to the horizontal plain in which the laser is already (...) (24 years ago, 10-Aug-00, to lugnet.robotics)
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