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2D Mapping Suggested Beacons?

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Ratfink:
Some questions about the suggested beacon would they not interfere with each other or the Sharp distance sensor?

Im assuming your suggesting i use a detector which rotates and the angle at which the beacon is detected use the information as triangulation to work out the distance between the detector and each beacon and finally work out the position of the car with these relative distances?

Admin:

--- Quote ---Some questions about the suggested beacon would they not interfere with each other or the Sharp distance sensor?
--- End quote ---
to my knowledge, the only thing that can interfere with a sharp IR sensor is another sharp IR sensor positioned badly . . . if your beacon LED's use visible light (green, blue, red, etc), its impossible for them to interfere with the IR spectrum :P

oh, and make sure you get the diffused light LEDs cause the clear ones are highly directional.

hgordon:
This won't give you distance, but it will give you rough orientation.  You don't need to rotate the detectors - they can be fixed, and you can use the fact that the field-of-view overlaps between the detectors to figure out in which quadrant a beacon is located.  So for example, if a beacon is straight ahead, the signal might only appear in the front-facing detector, but if it's 45-degrees to the right, it will appear in the front and the right detectors.  Also, you could rotate the robot to search for beacons.

As regards interference, the Vishay sensors have a 38kHz (with the 1738) filter, so you want to modulate the beacon at 38kHz with a bit pattern that uniquely identifies each beacon.  You would put a random delay between each burst of bits so it's not a continuous transmission.  I don't know about the Sharp range finders - perhaps the beacon would interfere, but since it's not continuous, you should be able to filter it out.  Actually, you might have better results by combining IR beacons and ultrasonic rangers.




--- Quote from: Ratfink on February 18, 2007, 04:15:10 PM ---Some questions about the suggested beacon would they not interfere with each other or the Sharp distance sensor?

Im assuming your suggesting i use a detector which rotates and the angle at which the beacon is detected use the information as triangulation to work out the distance between the detector and each beacon and finally work out the position of the car with these relative distances?

--- End quote ---

Ratfink:
Im quite keen on the following idea:

http://www.restena.lu/convict/Jeunes/beacon.htm

although im assuming that at the distance im looking at 20m-30m the inaccuracy would be even greater and the transmitter/reciever would be even more expensive.

I have a budget of roughly $400 or 200 pounds since im from UK

My university normally gets their components from:
http://uk.farnell.com
rswww.com/

I really like the idea in the link but im assuming a encoder would be better to use due to the greater inaccuracy of a 20m range beacon network.

Anyone have an idea of anything that would work similar to above with better results 10cm-15cm inaccuracy is fine with me within a 30m^2 area of space.

Admin:
if you have the camera already working, i still think you should just use only the camera. if you have a sign of known shape and size, you can easily calculate the robots exact position with respect to that sign. if you put simple colored leds around the room, the camera can tell which beacon it is looking at.

another beacon idea i have, and will probably build sooner or later, is a robot that does triangulation using not the timing of sound, but the amplitude of sound.

for example, close your eyes. now someone sneaks up to you and yells. now can you point to this person accurately without seeing him? yes, and this is because one ear hears the sound louder than the other ear, allowing you to discern the location of the person yelling. all you need is a single loud beacon (it could be ultrasonic so it wont annoy people), two microphones, and a sound absorbing object between the microphones (humans use a thick skull).

after all, running a high accuracy timer that can measure the speed of sound from three separate beacons is a huge waste of processing power . . . two simple ADC is so much simpler . . .

but again, i still say stick with your working camera . . . :P

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