Mecanum wheels under varying loads

[Alan Anderson]

Originally Posted by dellagd

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]

Originally Posted by dellagd

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]

Originally Posted by Robot Sans

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]

Originally Posted by Ether

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

Why not a ball caster?

[howe]

Originally Posted by Tom Line

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]

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

[Caleb Sykes]

Originally Posted by Chinske4296

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

Are the omni-wheels powered?

[Ether]

Originally Posted by Chinske4296

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

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

[gpetilli]

Originally Posted by Ether

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]

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?