Chief Delphi - Mecanum wheels under varying loads

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Technical Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=22)

- - Mecanum wheels under varying loads (http://www.chiefdelphi.com/forums/showthread.php?t=133500)

Alan Anderson

26-01-2015 12:39

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by dellagd (Post 1434109)

Ive also been curious about 'perfecting' a mecanum drive system by taking the load on each wheel and programming the drive to account for the uneven loading.

Varying the normal force "load" on each wheel has two primary effects. One is a subtle change in the wheel speed vs motor voltage. That can be compensated for using closed-loop control of wheel speed. The other is a significant change in the maximum thrust that the wheel can apply before slipping. That one is not so easy to account for, though I suspect monitoring the motor current can provide a way to do traction control and turn the wheel slip problem into a maximum robot acceleration problem.

Ether

26-01-2015 12:58

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by dellagd (Post 1434124)

I'm guessing doing the complete analysis would be pretty complicated

Yeah I think so. Alan's post#16 does a pretty good job explaining why load affects mec behavior and possible ways to deal with it.

Other options to deal with it involve using actual vehicle motion sensors (e.g. gyro, encoders on follower wheels, etc) to make corrections to the driver's commands.

Ether

26-01-2015 13:08

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by Robot Sans (Post 1434117)

Yup, thats what i was thinking. They would have to be low friction but not omni-directional. Plastic wheels would be ideal.

Why not omni? and what effect do you think those wheels might have on the mec's kinematics?

Daniel_LaFleur

26-01-2015 13:15

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by Ether (Post 1434141)

Why not omni? and what effect do you think those wheels might have on the mec's kinematics?

Why not a ball caster?

howe	26-01-2015 13:42

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by Tom Line (Post 1434074)

http://www.chiefdelphi.com/forums/sh...hreadid=133086

http://www.chiefdelphi.com/forums/sh...hreadid=132855

http://www.chiefdelphi.com/forums/sh...hreadid=121317

Google search terms:
mecanum wheel load uneven site:chiefdelphi.com

I usually have much better luck with Google's search than Chief Delphi's.

Thank you Tom, for the information I was looking for.
Thanks for the other tip too, sometimes I just can't help myself.
howe

Chinske4296

27-01-2015 11:46

We currently have a mecanum setup with omni wheels in between.

Caleb Sykes

27-01-2015 12:09

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by Chinske4296 (Post 1434661)

We currently have a mecanum setup with omni wheels in between.

Are the omni-wheels powered?

Ether

27-01-2015 12:31

Re: Mecanum wheels under varying loads

4 Attachment(s)

Quote:

Originally Posted by Chinske4296 (Post 1434661)

We currently have a mecanum setup with omni wheels in between.

in between how? A, B, C, D, or something else?

gpetilli

27-01-2015 13:55

Re: Mecanum wheels under varying loads

Quote:

Originally Posted by Ether (Post 1434690)

in between how? A, B, C, D, or something else?

Also, are all the wheels at the same frame height or is the "in between" wheels dropped (by 1/8")?

pafwl

27-01-2015 22:35

Re: Mecanum wheels under varying loads

With the unpowered omni in the middle I am guessing that you may have issues getting over the humps.

Are you using Andy Mark or VEX?

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