More Mule then Rover?

[Tommy_T]

more baby steps on way to four wheel drive.

[jwatte]

Very nice!

But will it have four-wheel independent steering? :-D

[Tommy_T]

But will it have four-wheel independent steering?

jwatte, I'm wondering that also.

with the front motors not connected to the front wheels turning is a battery sucking operation
with these fat wheels on pavement and the bucket installed. should be better with chains on the tires.
and the tires should last longer.

with the motors connected and chains installed I hope to be able to do zero radius turns with a full bucket
without drawing over 100Amp.

I got a Sabertooth 2x60 for this build, but seems the Sabertooth 2x32 may be better for the batteries I'm using.
I got the 2x60 thinking I was going to be adding 2 more batteries, plans change.





should have the front motors installed in 2 weeks, then I'll know if I need to look into
all wheel steering.


I would't want to play with the mule on my lawn right now(dragging the front wheels around)
but is fun to play in the sandbox.

[jwatte]

2x32 may be better for the batteries I'm using

Using a bigger controller is not a problem in itself -- it just gives you more margin for error. The only reason to use a smaller controller is if space or dollars are a constraint. FWIW, I've learned that a 2x margin in ratings of controller versus stall current of motor is about the right safety margin for me :-)

Will you still do tank steering, or are you considering articulated wheels? (Maybe go-cart style simple-pin steering, with a linear actuator pushing it sideways?)

[Tommy_T]

Using a bigger controller is not a problem in itself

jwatte, difference between Sabertooth 2x32 and the Sabertooth 2x60 is more about convenience to me.
with the 2x60 a max232 chip and pc software(describe) are needed to set things like current limits, the 2x32 has
a usb communication hub built in, with the 2x32 I can set things like Acc/Dec and current limits without the need
to swap wiring and changing dip switches(which is priceless when it's cold outside).

the mule does not have an on-board PC for this build.

I'm also wondering if my current batteries can supply the 200Amps that (2) Sabertooth 2x60 could draw.
I have blown a number of 100A fuses over the years with (1) Sabertooth 2x60.

Will you still do tank steering

Plan A is to do skid steering, and I also want to be able to do ZRT.

I tested an idea today that seemed to work.

I lowered the bucket all the way down, then tilted the bucket down until the front wheels came off the ground
then did a ZRT with ease, sliding around on the tip of the bucket(this would only work on hard surfaces).

[jwatte]

sliding around on the tip of the bucket

Good thing this is not your lawn mower robot :-)

[Tommy_T]

Good thing this is not your lawn mower robot

jwatte, not this season, but next summer it is.

this problem became obvious the first season's build(mowing), the first build used open-loop
control of the drive motors which ended up creating divots in the lawn when doing ZRT with
just two fixed wheels on the ground, with four it would leave divots even with closed-loop control.

all of the different option(plow,bucket,mower) have been designed as attachments.

next fall's build is replacing the bucket with a plow(four wheel drive plow is hours of entertainment).

[jwatte]

Better watch out! If you're not careful, you'll end up with a robotic farm to sustain you through the coming climate apocalypse, and then where would you be?

[Tommy_T]

more baby steps.

coming climate apocalypse

jwatte, I'm very slow with my climate apocalypse preparations , I can collect only 300gl
of rain water so far.

[jwatte]

Love it :-)