Re: [mowbot] Ultrasonic hardness measurement

Dave Everett (Deverett nospam at
Thu, 26 Sep 1996 08:11:41 +1000

Monta Elkins 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.

That's why I'm doing the experiment Monta, so *I* can be sure!
> 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

No we wouldn't, we'd have to distinguish between hard and soft surfaces.
This sensor isn't meant to be everything, it's one of perhaps many.
> Thats why I'm so interested in 'position' technology.

That's why I'm not. I suggest you review the results of positional work
related to robots to date. Pay close attention to the fact that the best
performers all required specialised environments.

What we have to produce is a robot that responds to the world, not a
disjointed fusion map of the world, not an uncertainty grid, not a cost
grid. This is a real-world project.

Dave Everett                                Email: deverett nospam at
(c) 1996 - Copyright remains with the author unless explicitly stated