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, 3 Aug 2000 07:16:40 GMT
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Viewed:
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1517 times
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Hi Mario, Mauro,
"Mario Ferrari" <mario.ferrari@edis.it> writes:
>
> Some free thoughts about this topic:
>
> 1) With a differential drive setup, you could use two rotation sensors both
> for navigation between landmarks, and for collision detection: when the
> wheels are supposed to rotate (motor on) but don't, you know you are against
> an obstacle. Very simple but effective. You now can use the third sensor
> port for a light sensor bound to landmark detection.
I tried to get away with a single rotation sensor on a
differential drive (put it on one of the output), assuming
that I one motor is not moving I could deduce total
movement. Unfortunately the turning motor drifts slightly
on forward/backward motion, so the thing is not going
straight.
> 2) A grid of tape on the floor works very well as
> artificial landmark. Use different color for the
> horizontal and vertical lines, so you're sure of what kind
> of line you crossed.
I have a natural landmark in the form of a checkered kitchen
floor, I'd like to try that for navigation. It's a little
more complicated I guess.
> 3) A different landmarking approach could be using a laser beam to query
> some base stations (if you're open to use a non-Lego laser pointer). The
> idea is you have a roating laser pointer connected to a motor and a rotation
> sensor (multiplied to increase resolution). When the robot wants to
> calculate its position, it stops and starts slowly rotating the laser beam.
> The base stations have a light sensor positioned at the same height of the
> laser beam. When the light sensor gets hit by the laser light, it reads
> almost 100% and the base station transmit an IR message to say "got it".
Almost 100% is an understatement, a laser really saturates a
light sensor. The problem is hitting it in the first place,
I found that next to impossible to achieve. I'd rather go
for some strobe lights (good for identification by rhythm),
or maybe halogene lights, with the light sensor on the robot
like scanbot in Dave Baum's book. I also tried candles
once, but they are to dim, they can be seen only from a
short distance, on the order of 10cm.
Jürgen
--
Jürgen Stuber <stuber@loria.fr>
http://www.loria.fr/~stuber/
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Message has 5 Replies:
 | | Re: Autonomous Robot
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| I explored the use of a single rotation sensor to make a robot drive straight here: (URL) can use a differential to take the difference of the two motors' output; if the motors are not moving at the same speed, you'll see some movement on the (...) (25 years ago, 3-Aug-00, to lugnet.robotics)
| | | Re: Autonomous Robot
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| (...) Great approach :) ! Using "hardware" to "calculate" the delta, instead of doing it by software, "wasting" a second rotation-sensor. Great :) (...) Yup, just like every multi sensor-enabled living beeing, using a mix of memorised (/learned) map (...) (25 years ago, 3-Aug-00, to lugnet.robotics)
| | | Re: Autonomous Robot
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| That's what they use for gps positionning in cars : they both use the gps signal for raw positioning and wheels rotation for precise positionning. A bit like using two systems for the same task... Philippe (...) Philippe Jadin Votre site web en un (...) (25 years ago, 3-Aug-00, to lugnet.robotics)
| | | Re: Autonomous Robot
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| (...) The proposed solution in the "Robot Tracking" thread sounds like it's exactly what's needed here. From the original post... (...) track the robot throughout a 20 ft x 20 ft room at a 1 Hz rate with an accuracy of 1-2 inches. In principle, the (...) (25 years ago, 4-Aug-00, to lugnet.robotics)
| | | Re: Autonomous Robot
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| (...) rotation (...) beam. (...) the (...) A direct hit is really almost impossible. That's what I found in mosts post about this matter. But if you aims that in a reflective convex surface, it will probably hit a light sensor in the emitter but (...) (25 years ago, 4-Aug-00, to lugnet.robotics)
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Message is in Reply To:
| | Re: Autonomous Robot
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| Hi Mauro I find your project very challenging, being navigation one of my main interests inside Lego-robotics. About 18 months ago I made my first experience with pure odometry (no external landmarks) and found that in the short range it is *very* (...) (25 years ago, 2-Aug-00, to lugnet.robotics)
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