Subject:
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Re: Autonomous Navigation
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 15 Aug 2000 11:27:27 GMT
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Original-From:
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Andy Gombos <gombos_2000@(avoidspam)yahoo.com>
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Viewed:
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657 times
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You could use the tower, and a range finding sensor at the top, with a
laser pointer. The laser pointer could be used to detect the position of the
robot it the "x" position, and then the range finder could be used to figure out
the distance to the robot, which could be used to calculate the actual distance
to the robot, using triangles. You would end up with a latitude/longitude kind
of system though, because of the circular nature of the laser pointer's
spinning.
You could also not use a tower, but just have a base, and calculate the
position directly, by using the range, and the reflected light position.
Andy
Conrad Labuschagne wrote:
> OK here is an idea i got last night:
>
> I built a roverbot, and on top is a "radar". The radar is a large turntable
> powered by a motor with a lightsensor inside, mounted vertically facing up
> onto a mirror mounted at 45deg. The radar rotates and all light in the
> cricle sweep is reflected onto the light sensor. (it looks quite cool in the
> dark with the red light rotating). Attached to it is a rotation sensor. The
> idea was to scan for high light levels and when found, rotate the robot
> while counter-rotating the radar until the light source is in front of the
> robot. Then just drive forwards towards the light. Now for the second idea,
> if we had an arena with four light sources in known positions, the robot can
> just scan the area to find the light sources and by knowing the position of
> each soucre found, calculate it's position relative to all the light
> sources. Off course you could modulate the light sources and use IR sensors
> for the radar if you needed to operate this in sunlight and just increase
> your IR emitters to increase the range. Now the robot can constantly
> pinpoint it's position.
>
> I put the 5th light source for added accuracy, i suppose any geometry might
> work.
>
> *=light source
> R=robot
> |-=arena
>
> *-----------*-----------*
> | |
> | |
> | |
> | |
> | |
> | |
> | R |
> | |
> | |
> | |
> *-----------------------*
>
> COMMENTS????
>
> Conrad
>
> -----Original Message-----
> From: Sattler Chris-QA1406 [mailto:Christopher.Sattler@motorola.com]
> Sent: Tuesday, August 08, 2000 19:23
> 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:
 | | S@H Information
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| Hi, My wife is over in the US at the moment, and wants to get me some spare parts. Can anyone tell me the phone number for S@H? and where I can find a catalogue, so I can give her some part numbers? (I am after come compressor pumps etc.) Also what (...) (24 years ago, 15-Aug-00, to lugnet.robotics)
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Message is in Reply To:
| | RE: Autonomous Navigation
|
| OK here is an idea i got last night: I built a roverbot, and on top is a "radar". The radar is a large turntable powered by a motor with a lightsensor inside, mounted vertically facing up onto a mirror mounted at 45deg. The radar rotates and all (...) (24 years ago, 15-Aug-00, to lugnet.robotics)
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