Robot Positioning System
Philldapill
Posts: 1,283
As many forums members have found, GPS units aren't that accurate on the <25 feet range. If you are trying to pinpoint a location within 25', it's just not doable with GPS. I'd like to get a discussion going in this thread that targets different methods of monitoring the position of things, such as a robot.
The primary method that I've been toying with, is using a series of becons with a fixed, known location. The method involves triangulation with these becons, using a radio signal.
The device that will be located will emit a "request" signal which all the becons will detect, then re-emit a return signal. The device will then watch how long it takes for each return signal to come back. Basically, EM echo location... The electronics would have to be extremely fast in order to achieve any decent results. To give an idea, if the resolution of the device is 1ns, then the physical location resolution would be about 0.33m.
Any thoughts on this method? Electronics have made leaps and bounds over the years, so I'm wondering if this would be feasible now... Also, other suggestions are more than welcome!
The primary method that I've been toying with, is using a series of becons with a fixed, known location. The method involves triangulation with these becons, using a radio signal.
The device that will be located will emit a "request" signal which all the becons will detect, then re-emit a return signal. The device will then watch how long it takes for each return signal to come back. Basically, EM echo location... The electronics would have to be extremely fast in order to achieve any decent results. To give an idea, if the resolution of the device is 1ns, then the physical location resolution would be about 0.33m.
Any thoughts on this method? Electronics have made leaps and bounds over the years, so I'm wondering if this would be feasible now... Also, other suggestions are more than welcome!
Comments
GPS sucks as far as to an inch accuracy goes, This is the accuracy that I need (1 INCH)
I see You have run into the same problem I have with using RF for Triangulation. Following its EMF echo sounds HOOKY at best
But I feel it deserves investigation.
I'll look into this EM echo.
The main problem is the slow-for measuring RF speed of the $STAMPS
Good Post
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http://www.richardvannoy.info/laser-navigation.pdf
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Richard Vannoy
Programming and Electronics Instructor
www.RichardVannoy.info
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I like your idea from the point of simplicity. I see a few problems though. What if a receiver on the bot can "See" two transmitters·at the same time, it might be difficult to sort them out.
Have you looked at how Aircraft navigate using VOR stations? http://en.wikipedia.org/wiki/VHF_omnidirectional_range
I have been doing some thought experiments with a variation on VORs.
Like your Idea, you would have a set of fixed transmitters in known locations.
I would use a directional light source at the transmitter. Could be IR or Laser or LED. Each transmitter would have the light source behind a rotating shutter. think of an opaque plastic tube with a slit in it. The plastic tube would rotate so an observer could only see the light emitter (on the inside of the tube) when the slit rotated toward them. The transmitter would also need an Omni directional beacon that flashed when the slit was facing a pre-determined direction (North).· Now an observer (receiver) could time the difference between the Omni directional beacon and when it observed the second pulse. In other words, the time between the two pulses would equate to compass angle from the transmitter.
You could still have the problem of the receiver seeing two or more transmitters and getting confused. To solve this, I thought that the·the transmitters to do some sort of arbitration so that they took turns and only one would on at a time. If the shutter was rotating at say 100 RPM then you could theoretically approach 100·transmitters and get an update from each of them once a second. A more realistic number would be 4 or 5 transmitters at 100 RPM and you would get updates 10 times per second from each.
To go further you could·encode the·transmitter ID# into ·the Omni directional sync pulse.· You could of course do this with a circular array of LEDs so there would be no moving parts. If you use the moving shutter, it would need to have a process to ensure it rotated at a know speed.
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The downside is that this is more complex that a reflector or repeater and the transmitters would be a small project in and of themselves.
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Searider
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- Stephen
good video's too
James
Silly Me
If the post gets back around to GPS modules and positioning let Me Know.
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The Truth is out there············································ BoogerWoods, FL. USA
The discussions are, as you pointed out in your first post, about positioning, and again, per your first post, GPS is recognized as "not the way". Specifically, the thread is looking at alternatives to GPS that provide a higher level of resolution (i.e. more accurate location).
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John R.
Click here to see my Nomad Build Log
Post Edited (John R.) : 8/1/2009 4:09:39 AM GMT
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·"If you build it, they will come."
Richard,·· I would also like to see more on your project.
agfa