DIY robot lawn mower

[Tommy]

I'm interested in the results of your test run on Sunday. Please keep us posted

Two-Stroke, tests cut short by Mother's day commitments.

As is the Mule has two devices for maintaining a straight cut path. The first a Yaw sensor, second
a USB digital compass, I only tested the compass because after lots of head scratching and lots
of unneeded software changes I discovered the Yaw sensor was interfering with the compass and
had to be removed for this test.

The tests of the digital compass showed it to be a useful but limited sensor, while in a open field
it was able to keep the Mule on a set coarse to +- .3 deg over the 850ft path(Sweet!), but while
in an area with large metal objects(cars, storage sheds, etc..) the Mule could not maintain a
bearing, the objects would change the magnet fields causing the Mule to change coarse(crap!).

an interesting test would be to see if the digital compass could be used to map out the Mule's
environment using magnet fields kinda like an MIR(Magnet Imaging Radar).

Tommy

 

[mystreba]

an interesting test would be to see if the digital compass could be used to map out the Mule's environment using magnet fields kinda like an MIR(Magnet Imaging Radar).

This may sound crazy, but would it be possible (cost notwithstanding) to use radar or lidar?

GPS?

 

[Two-Stroke]

Tommy -- thanks for the update.

 

[Tommy]

but would it be possible (cost notwithstanding) to use radar or lidar?

mystreba
LIDAR(or Laser ranging) is a common tool used in military/Universities grade unmanned vehicles, but that
cost notwithstanding part keeps that technology off the Mule.

In the consumer electronics market(hobby robots) Ultrasonic range sensors are in common use, some
having ranges of 200ft at a cost of about $100us, but that technology is best suited for indoors use.
because temp, humidity and wind speed can change it's recorded values.

I can't see wind speed changing the magnet fields.

Tommy

 

[Tommy]

Update:

Completed tests of friction drive Reel mowers on George, and while it had it's advantages
it couldn't give repeatable results, too many things can stop the Reel from turning.

Options I can think of.
1) Motorize(electric) the Reel Mowers
2) Motorize(electric) a standard mower deck, something like a JD 38" mower deck.
3) Use multipliable over the counter electric mowers to make a 38" cut path.

The fastest(grass needs cutting) seems to be #3.

Tommy

 

[Jetblast]

Will there be a flat spot on top for my cat to sit so I can shoot a sweet YouTube video?

 

[Tommy]

Will there be a flat spot on top for my cat to sit

Jetblast, your cat better have nerves of steel, because these electric mowers make
as much noise as a gas motor.

while test mounting the 2 24vdc rotary mowers I found I could not get them closer
then 1.5" together without cutting parts(destroying the mower), going to test using
a caster at that split in hopes it diverts the grass to either mower.

Tommy

 

[Tommy]

Update

First tests of the 38" electric mower deck went good, wasn't stopped by tall grass(~8") or
the last years bits and pieces of corncobs(stuff that would stop the Reel mowers).

Not happy with the size(footprint) of the test unit, I did like the small footprint of the Reel mowers.

Tommy

 

[Two-Stroke]

Thanks for the update, Tommy.

How is the guidance system? I think you said that you were going to test how accurately George can navigate.

 

[Tommy]

How is the guidance system?

Two-Stroke, I'm still working with the digital compass because it did keep the Mule
on a straight heading with the reel mower, yes it did waste a lot of energy trying
to turn the reel mowers with its six fixed wheels spring loaded to the ground but
it did work, the electric rotary deck I'm testing now has two casters to maintain
cut hight which can turn any direction with little effort from the Mule which should
require less energy(from the drive system).

I did test the compass as it was set up for the reel mowers, but the electric motors
on the new test deck interfered with it's reading, last night I did get a chance to move
the compass to a new location and should know today if interference is gone.

some quick calculations seems to suggest that to cut 4"(off the top) of grass in a 4 acre
field using a 38" electric deck would require close to 300Ah of batteries, while cutting 1" (off the top)
would need 120Ah.

I hope to get a chance to replace the mulching blades with standard blades to see if the
energy requirements change.



Tommy