🚀 go-pugleaf

 klaus@captain-crunch.ai.mit.edu (Klaus B. Biggers) writes
> In article <20073@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU
> (Chris Phoenix) writes:
>>Another possibility:  Bury a wire under the yard, and make your
machine follow
>>the wire.  This is simplest--you don't even need a computer.  But it takes a 
>>lot of wire for a big yard, and you have to worry about something
breaking the
>>wire.  (Of course, you have to worry about something removing the reflector,
>>too.)  I don't know what kind of circuitry you need to make this
work--I would
>>guess an RF generator you hook up to the wire, two antennas on the machine,
>>compare the signal strength from the antennas to decide where to turn.
>>
>>If anyone has any feedback on anything I've said, please tell me, either in
>>e-mail or on the net.  Thanks!
>
> 
>I like that idea best... I saw an add the other day by a company
>called invisible fence. You bury a wire around the perimeter of your
>yard and then put a special collar on your dog. When the dog gets
>close to the wire, his collar beeps, and if he continues on, it then
>gives the dog a mild shock. It seems you could use this type of
>approach to tell the mower to turn around but not completely. It may
>be possible to just let the mower make a random pattern over your
>yard.. It would eventually cover all of it ...

Around 1964 (that's right, almost 30 years ago) there was a construction
 article in Radio Electronics describing a mower built on the wire follower
 principle suggested by Chris.  It described how to convert a conventional
 power mower by adding drive motors and control electronics.

A year or so later a commercial product, called the "Mowbot", appeared,
 costing about $2000, that used the "boundary bounce" principle suggested
 by Klaus.  Trees were put off limits by running the (buried) boundary wire
 from the property periphery to the tree, around it, and then back to the
 periphery by the same route. The colinear wires between the periphery
 and the tree were invisible to the mower because the opposite directions
 cancelled the signal.  The turtle-like car-battery-powered Mowbot had
 small, safe, cutter blades, and depended on persistence to get all the
 grass.  It was too heavy to move around by hand, but had a plug-in manual
 control "leash" that let one drive it to its recharger.  There did not seem
 to be a great market for a $2000 lawnmower, and I never heard of it again.

                       Hans Moravec <hpm@cs.cmu.edu>