Author Topic: distance sensor  (Read 4160 times)

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Offline fenghua9801Topic starter

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distance sensor
« on: May 13, 2007, 11:10:44 AM »
Hey, I want to find a distance sensor which has the following specifications:

10 meters range
5Hz frequency
5cm resolution

Most important, it should be robust against distubance

I have searched many types of sensors, such as sharp IR sensor and sonar sensor. It seems that they can not achieve so large range.   :'(

The only feasible one is the laser sensor. However, it's too expensive. Does anyone have the experience of buliding a laser distance measurement sensor?

Thanks!

Offline dunk

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Re: distance sensor
« Reply #1 on: May 13, 2007, 05:13:31 PM »
Quote
The only feasible one is the laser sensor. However, it's too expensive. Does anyone have the experience of buliding a laser distance measurement sensor?

have a look at he 6th post down on this thread for a description of mine:
http://www.societyofrobots.com/robotforum/index.php?topic=242.0

dunk.

Offline fenghua9801Topic starter

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Re: distance sensor
« Reply #2 on: May 14, 2007, 04:44:20 AM »
Dunk, thanks for your info.

I have read your camera plus laser method.  Seems you use the sensor indoors. However, i plan to use it
outdoors. If there is bringt sunlight, Does your system still work well?

Moreover, I need a compact solution. your solution seems cubersome.

Ps what about the resolution of your system?

Thanks very much.

Offline Admin

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Re: distance sensor
« Reply #3 on: May 14, 2007, 07:43:12 AM »
Ill have to agree with Dunk on this, with your budget constraints I cant think of anything better . . .

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what about the resolution of your system?
its equal to the resolution of your camera

Offline dunk

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Re: distance sensor
« Reply #4 on: May 14, 2007, 12:17:02 PM »
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If there is bringt sunlight, Does your system still work well?
to be honest, i still haven't finished this robot's motor controllers (any day now) so the sensor still hasn't been mounted on the robot or been outside.
but yes, i'd imagine bright sunlight would decrease the effectiveness quite a lot.

i think you would get 10 meters range as long as you use a bright enough laser and use a high quality web cam though.
(a high quality web cam would start adding to the cost though....)

Quote
your solution seems cubersome.
if you have a processor with a USB host port capable of accessing a webcam on board then the individual components are quite small but you do need to mount them a distance appart.
(the further appart, the greater the accuracy.)

if you don't have a processor with a USB host port on board then you are going to need one, making it very cubersome and quite expensive...


good luck and let us know if you find anything better.

dunk.

Offline JonHylands

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Re: distance sensor
« Reply #5 on: May 14, 2007, 01:01:41 PM »

Offline Admin

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Re: distance sensor
« Reply #6 on: May 14, 2007, 01:51:37 PM »
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http://www.acroname.com/robotics/parts/R14-SONAR1.html

"This module, with a simple interface, is able to measure distances from 6 inches to 35 feet."

haha I stand corrected . . . stupid technological advancements . . . :P

Offline JonHylands

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Re: distance sensor
« Reply #7 on: May 14, 2007, 02:20:14 PM »
Actually, that module has been around forever - its the new ones that don't have the same capability...

You used to have to hack the module after it was removed from a Polaroid camera, but now you can buy a board that is set up properly.

- Jon

Offline dunk

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Re: distance sensor
« Reply #8 on: May 14, 2007, 02:43:47 PM »
so sonar is great for determining the range of an object but difficult to focus.
the "Typical Beam Pattern At 50 kHz " diagram on this page
Quote
http://www.acroname.com/robotics/parts/R13-INST.html

suggests about a 20 degree field of view.
at a range of 10 meters you'll get a horizontal resolution of around 3.5 meters.
even with clever overlapping of scans you won't get close to the desired 5cm resolution.

dunk.

Offline JonHylands

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Re: distance sensor
« Reply #9 on: May 14, 2007, 02:57:44 PM »
Well, he said 5 cm resolution - typically, with a range-finder, resolution refers to the distance measurement, not the horizontal/vertical resolution.

Or if it does, the OP needs to be more specific. You're not going to get anything other than a laser or a camera to resolve a 5cm object at 10 meters...

- Jon

Offline fenghua9801Topic starter

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Re: distance sensor
« Reply #10 on: May 14, 2007, 08:42:07 PM »
Well, he said 5 cm resolution - typically, with a range-finder, resolution refers to the distance measurement


Yes, the resolution means the  distance measurement.

Can you guys see this sonar range finder:
http://www.airmartechnology.com/Uploads/AirPDF/AT75.pdf

seems good, but maybe expensive

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Re: distance sensor
« Reply #11 on: May 15, 2007, 04:40:35 AM »
you will need a sonar driver for that . . .

 


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