piclist 2008\07\31\003026a >
Thread: Beacon system for position location
www.piclist.com/techref/index.htm?key=beacon+system+position
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face BY : Forrest Christian email (remove spam text)



A few "brainstorming" thoughts...

The big one:  Make the rover as dumb as possible.  Putting this
intelligence in the mower is silly...  Build this in an older PC or
similar, and then have the radio control simply provide direction to the
mower.   That is, the PC will determine where the mower is now, and
where it needs to go, and tell the mower to move say left or right or
forward or backward.

So, then you simply have to know where the rover is, within a few
inches.  Ideas:

1) Use radio direction finding.   Place a "beacon" on the mower - just a
transmitter on a specific frequency, no modulation or anything.   In the
yard area place one or more receivers which can detect phasing
differences between two antennas.   The simplest way to do this is with
a pair of antennas and an antenna switch to switch between them, hooked
into a FM receiver on the same frequency.    With suitable signal
processing, this will give you an angle from the antenna where the rover is.

2) Use high resolution video and some sort of video processing...  You
will need to ensure something like 1 inch per pixel or similar and then
write some code to locate the mower.  You should be able to make this
easy to locate by painting it fluorescent orange or similar.   Of note,
a 1024x768 camera should be able to handle an 85x64 ft yard if you can
mount it in the right spot and one inch per pixel is sufficient
resolution (subject to experimentation).  These are commonly available
for less than $40 in the form of a USB webcam.   I think this is where I
would start..  The loop would look something like: grab a picture, look
for orange.  Figure out where it is in relation to where it needs to
be.  Command the mower. Repeat.

-forrest
<48913FD3.4070101@imach.com> 7bit

In reply to: <Pine.LNX.4.64.0807301733000.5314@www.sportsmogul.com>
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