Author Topic: Mowing Grass with four wheel drive (The test)  (Read 895 times)

0 Members and 1 Guest are viewing this topic.

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Mowing Grass with four wheel drive (The test)
« on: August 11, 2013, 10:30:30 AM »
Everything tells me four wheel drive would suck at mowing grass, but there may be a minimum turn radius
that could be used that would cause no damage to the lawn.

best way to find out would be to try it.

first image is of the test frame for this project.

Second image is of wheels that'l be added to the test frame.

currently on the test frame there are two 350W 24Vdc Motors with a 3 to 1 gear reduction and 18" wheels.
I'm adding two 1000W 24Vdc with 5000 cpr encoders Motors that are directly connected to 14" wheels.

Tommy

Offline jwatte

  • Supreme Robot
  • *****
  • Posts: 1,343
  • Helpful? 81
Re: Mowing Grass with four wheel drive (The test)
« Reply #1 on: August 11, 2013, 05:42:39 PM »
If the castors at the back of the bot are idle (not powered) then differential steering will probably not tear up your lawn. That only happens when you use four-weel-drive with differential steering.

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Re: Mowing Grass with four wheel drive (The test)
« Reply #2 on: August 11, 2013, 06:48:33 PM »
 
Quote
That only happens when you use four-weel-drive with differential steering.

And that's the plan, on the test frame(top picture) I'm removing the casters and replacing with
motor driven wheels(2 at 14"x 5"), and use differential steering.


front two motors are 60rpm max with 18" tires
back two motors are 160rpm max with 14" tires

Tommy 

Offline shimniok

  • Jr. Member
  • **
  • Posts: 11
  • Helpful? 0
Re: Mowing Grass with four wheel drive (The test)
« Reply #3 on: August 21, 2013, 08:26:26 PM »
Cool project!

I vaguely recall a picture of a robo lawn mower years ago in a robot book that had omni steering or at least, all the wheels were connected with sprocket and chain so the wheels were always pointing in the same direction but could be rotated 360 ... I would think skid steer would be a bit tough on the grass too. And maybe not as great for minor course correction. What about ackerman steering? With rear wheel steer (or even 4 wheel steer, like 4x4 rock crawlers) for improved maneuverability. That should be easy to build right? :D
Michael Shimniok
http://bot-thoughts.com/

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Re: Mowing Grass with four wheel drive (The test)
« Reply #4 on: August 23, 2013, 07:45:24 AM »
Quote
I would think skid steer would be a bit tough on the grass too.
shimniok, I also have very little confidence that four wheeled skid steering would
be a practical configuration for mowing grass, the added power requirements(more batteries)
, and the damage to the lawn as just a few of the drawbacks.

Quote
With rear wheel steer (or even 4 wheel steer, like 4x4 rock crawlers) for improved maneuverability. That should be easy to build right?
The test frame I'm using makes changing rear end configurations very simple(two bolts),
so testing ackerman, casters, two wheeled skid, four wheeled skid or and other types
should be simplified.

Tommy

     
« Last Edit: August 23, 2013, 07:47:02 AM by Tommy »

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Re: Mowing Grass with four wheel drive (The test)
« Reply #5 on: August 25, 2013, 03:11:19 PM »
I was able to free up some time this weekend and was able to swap out the rear casters with drive motors.

Tommy
« Last Edit: August 25, 2013, 03:15:53 PM by Tommy »

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Re: Mowing Grass with four wheel drive (The test)
« Reply #6 on: September 17, 2013, 05:54:31 PM »
With the mowing deck working now(picture below), I should have all the parts needed to test
FWD, But. stuck on which of the speed controllers I have to use for this test. the controller I want
to use is a sabertooth 2X25, But that drive I'm using on my bike(electric trike), I also have 2 P&G VSI
which are up to the job but matching the exc/dec profiles to the sabertooth 2X60 that I'm using as
my primary controller would be tedious.

Mowing deck = 44" cut path with two 20" electric rotary type, and one 15" reel type to pick up the
gap between the rotary's.

Tommy
 
« Last Edit: September 17, 2013, 06:00:14 PM by Tommy »

Offline briselec

  • Jr. Member
  • **
  • Posts: 10
  • Helpful? 1
Re: Mowing Grass with four wheel drive (The test)
« Reply #7 on: October 12, 2013, 03:46:20 PM »
what's the plan for controlling it? How will it know where to mow?
In assembly language no one can hear you scream

Offline TommyTopic starter

  • Full Member
  • ***
  • Posts: 112
  • Helpful? 3
Re: Mowing Grass with four wheel drive (The test)
« Reply #8 on: October 12, 2013, 09:06:29 PM »
Quote
what's the plan for controlling it?
briselec, it has a few different control option. 1) Manual Joystick, 2) FPV, 3) G Code(CNC Mode).

Quote
How will it know where to mow?
It has to be programmed in G-Code(non-standard format)
I use notepad to write and edit codes.

the line "Q45 C180 F30" tell it to turn 45deg using the Q axis until the compass reaches 180deg at 30% velocity.
the next line could be "C180 X320.5 F70" which tells it to hold a compass heading of 180deg until the X axis
reaches 320.5feet at a velocity of 70%.

Until I get the beacons working I have to start the program in the same spot each time.

picture below is FPV mode example
 

Tommy
« Last Edit: October 12, 2013, 09:10:45 PM by Tommy »

 


Get Your Ad Here

data_list