Re: [mowbot] What Happene

Dave Everett (Deverett nospam at
Sun, 01 Dec 1996 20:51:29 +1100

Raymond Skarratt u wrote:
> > > Surely we should exhaust all possibilities of onboard sensing before we
> > > ever contemplate beacons or any other artificial modification to the
> > > environment.
> I agree. I was just pointing out that if we are dealing with a
> relatively structured and small area that if we wanted to we could get
> much better than .2m accuracy. I do think that we at some point are
> probably going to have to have some sort of either passive or active
> beacons or boundary marker.

I was mainly concerned that this might turn into a purely theoretical
pursuit without any reference to actual real world trials. I've seen
many robot projects develop like that in the past. By the time they get
around to actually constructing a robot, it's been comprimised by
excessive theorising. I believe the key to a successful robotic project
is to only solve _real_ problems. I'm not saying that beacons will never
be necessary, just that at present there is no physically existing
problem for them to solve.
> > > >
> Ok, here's my attempt at throwing out some ideas in these areas. First I
> think that the cutting mechanism can be really crude (rasor blades on a
> plastic or metal disk) as long as we have some sort of saftey device that
> either retracts or totally disables or both the blades when something
> gets close to the mowbot or when it gets picked up.

The cutting motor can be 'dynamically braked', by taking both motor
terminals to either the positive or negative rail. One of the reasons
I'm keen on the weed trimmer head at the moment is because it poses less
of a safety problem than sharp blades. However as I've previously said,
I'm not *that* concerned about safety until the concept is proven
> Second, I thnk that the base can be relativly simple. A square frame
> made of angle irons comes to mind. We can then build a cover from
> whatever (everyone's idea can be different however,) I prefer fiberglass
> because it can be worked into whaht ever shape I want and I can paint it
> to make the mowbot look really sexy, which fits into the 'have a winning
> personality' goal of this project. :)

Yep, something simple so we can get started. I've ordered 2 DCM-64
gearmotors from All Electronics Corp, I just can't wait any longer <g>.
They may not be the perfect motor, and as Robin pointed out may not take
kindly to continuous operation, but comparable motors here cost about
$150 each and I have to wait 6 weeks for the gearboxes to be made
(shipping of the DCM-64's from the US are going to take 6-8 weeks)!

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