Re: [mowbot] Ultrasonic hardness measurement

robin nospam at
Thu, 26 Sep 1996 02:37:51 +0100

Monta Elkins <Monta nospam at> wrote:
> Dave Everett wrote:
> > I set up an experimental breadboard to test the possibility of
> > differentiating between grass and concrete.
> Thats pretty interesting, but I'm not sure it practical.
> We'd have to distinguish between:
> grass and concrete
> grass and asphalt
> grass and mulch
> grass and gravel / pebbles
> grass and lettuce
> grass and flowers

If all goes according to expectations, the ultrasound sensor will
do three out of the six (the hard things: concrete, asphalt, gravel),
and maybe even distinguish the soft mulch at the opposite end of the
scale. That's pretty good going for a sensor that costs pence.

> Thats why I'm so interested in 'position' technology.
As I have said before, I think a rough idea of position is important
for keeping track of which areas are due for a visit. But I don't
think it's likely we can make our position sensors accurate enough
to use them for routine boundary definition. It will be useful to have
a belt-and-braces check on the other boundary sensors though.

> I'd imagined leading mowbot around the yard once and saying,
> don't ever mow this (its my garden) or this (it's my driveway)
> or this (they're my wife's flowers) or anything past here
> (that's my neighbor's yard).
This might still be possible, but instead of remembering *where*
it is, Mowbot could be learning what driveway and flowers look like.


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