RE: [mowbot] Software discussion

Raymond Skarratt (skarratt nospam at
Wed, 22 Sep 1999 10:24:12 -0400

Yes, I am still around. I've been quiet but I have been listening....

I like your suggestion Dave. The two boundary requirements you mention
probably hold true for most people. I moved a few months ago and at my old
house the backyard was very open and there was no boundary between my
property and my neighbour's, and his neighbour's and his neighbour's. So I
could just imagine the mowbot cutting everyone's lawn. :-) That problem
would have been pretty easily overcome by putting up some sort of barrier
that would be strong enough to withstand an impact that would set off the
bump sensors. The problem that I have at my current house is that I have a
very steep drop-off on the edge of my property (~50 degrees). There is
grass right up to the edge (and even on) this drop-off. I know that short
of making a walking mowbot this drop-off will cause a problem for the mowbot
(it causes a problem for me :-) ). Again, this can be solved with a
sufficiently strong barrier. The other concern that I would have with this
solution is if some one happens to have a flower bed with dense plants close
to the edge of the bed that might fool the IR fingers. I know for me
personally that would guarantee a one way ticket to the dog house. :-) But
once again, this is a problem that could be solved with a suitable barrier.

I have to admit that I do have some ulterior motives here. Once I have a
working mowbot I would like to move on to a shovelbot. For some of you this
will not be an issue but in Canada we have to worry about snow shoveling. I
would like to come up with a solution that will at least partly apply to
both 'bots.

Anyway, good suggestion Dave. I hadn't thought of that although I was
thinking that the IR fingers thing would be an effective way to handle power
management since it would allow the disabling of the cutting motor when
there is no grass long enough to cut.


-----Original Message-----
From: Dave Everett [SMTP:deverett nospam at]
Sent: Tuesday, September 21, 1999 7:31 PM
To: mowbot nospam at
Subject: Re: [mowbot] Software discussion

At 09:52 21-09-99 -0400, Raymond Skarratt wrote:
>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.
Well Ray, good to hear you're still around mate :)

>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
>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.
I believe there are only 2 real detection requirements to meet the
spec of
a robot that covers the whole area and stays within the bounds.

For the purpose of this discussion I am proposing a simplified

1) the boundary region must be marked by either:
a) a solid fence at least 6" high
b) a non-grass region

2) the grass should be long enough to register with a set of slotted
fingers at the front of the robot.

The robot would use only these sensors:
1) Slotted IR fingers at the front (5 to 7 slots)
2) floating outer cover that produces bump information

Using these 2 sensors the robot would start on an outside edge and
it's way in feeling around obstacles until the entire region was

Dave Everett

Domestic Droids Website