Re: Radio direction finding for robots

From: Ken Taylor (ken_at_home.nz)
Date: 09/01/04 

Date: Wed, 1 Sep 2004 21:22:22 +1200

"Dingo" <nsjunkstuff@hotmail.com> wrote in message
news:4134577f$1@duster.adelaide.on.net...
> I merely wish to know the location fo my robot within a few rooms in my
> house. I would like it to plot itself as accurately as possible within a
> couple of rooms. Odemetery would probably be too sloppy in a normal house
> environment where lots of turns are need to avoid unexpected obstacles and
> lots of different types of surfaces and my lack of sourcing the right
sized
> stepper motors.
>
> I won't have line of sight so IR beacons won't work.
>
> Basically if I had three known location beacons and could find the
direction
> to them from my robot then the robot could offload the processing to a pc
to
> do the Trig and plotting of location on a known map.
>
> I was thinking "FM Bug" detectors or similar would be usefull (ie pretend
> the beacons are bugs) it all comes down to accuracy.
>
> I don't know about radio but with FM if you had two antenna spinning
around
> a central axis. Couldn't you "catch" the two points during 360 degrees of
> rotation where the signal was strongest or most in phase? then at least
you
> could draw one line on a map. Then just repeat with different beacons.
>
> Sorry for the long post :)
>
> Nigel
>

Well, if you're happy to put moving parts onto your robot, how about making
it a cylinder with a slot in it, rotated by a stepper motor (so you can
accurately determine where you're 'pointing'). Inside the cylinder is your
antenna, just a length of wire, essentially. Rotate the hole in the
cylinder, which otherwise shields the antenna (clue: make the cylinder
something RF shielding :-) and determine direction of max signal strength.
If you have two receivers (or selectable channels) you can seek different
beacons on different frequencies. Trig, etc is 'just computation'. I leave
the trivial details to your good self. :-)

Cheers.

Ken

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