[mowbot] Software discussion

Raymond Skarratt (skarratt nospam at ati.com)
Tue, 21 Sep 1999 09:52:21 -0400

Hi all,

Things have been a little quiet lately. I thought it would be good to get
another discussion going and hopefully get as many people on the list as
involved as possible.

I think it is pretty clear that everyone is going to have a slightly
different implementation of the hardware for the mowbot. Everyone will
implement the cutting mechanism slightly differently, everyone will have a
different implement for the frame or chassis, some people will choose to
have 2 wheel drive, some people will determine that 4 wheels might work
better for their property, the list of potential differences goes on. There
are some basic, fundamental elements in the design that will be common
through all implementations of a mowbot. The main thing that I think will
be fairly common across all implementations is path-finding or area coverage
or whatever you want to call it.

I think that this problem will make up the bulk of the necessary software
for any mowbot. Sure we can add things like alarms if some one gets too
close to the mowbot, safety mechanisms to shut down the cutting blades if
some one or something gets too close, and many other nice features. I do
think that anyone building a mowbot should include some safety features into
their projects but from a design standpoint I think these are sort of
trivial. I think that the main problem that we need to solve in software is
ensuring full coverage of an area in a timely manner.

So let's say for the purposes of discussion that we would like to see the
mowbot cover a specified area and not run outside this area. Let's also say
that we would like the mowbot to cover the area in a reasonable amount of
time. I think that I would probably like to exclude a random-path
implementation from our discussion. The random-path solution will probably
end up being a special case of any solution we come up with. One of the
main problems that I see will be boundary detection.

Ok, to start the discussion off I think we should probably start talking
about boundary detection. What I can think of right now are two ways that
boundaries can be detected. The first is to have some sort of perimeter
marking thing. Whether this is a low-voltage wire run around the perimeter,
a chain link fence that exists around the perimeter, or a light that is
beamed along the perimeter or whatever, they all fall into the perimeter
marking category. The other way I can think of knowing boundaries is
through the use of beacons. The distance from a beacon to the edge of the
perimeter is known and the mowbot always stays on the correct side of the
beacon. This solution will obviously require more than one beacon unless
you happen to have a circular property. :)

Ok, I think I have gone on long enough. I look forward to a lively