Mecanum Advice Request

[Todd]

Originally Posted by JonA

More details of what BigJ is talking about can be found in this paper about the control strategy used by FRC Team 1675. Basically the output is limited based on the inverse kinematic calculations to allow for maximum speed output of the robot to be the same in all directions with overhead for the yaw rate to be added allowing the same yaw rate control regardless of the heading. These calculations result in the reduction of total overall maximum speed (not using the full range when traveling in the forward/reverse direction) in favor of overall normalization of speed and yaw rate. "Beast Mode" basically allows the driver to override this control decision.

As Ether noted this year the math in the provided holonomic drive VI's corrects for this already and no optimizations are required to achieve optimal drive output, though this was an issue last year.

Originally Posted by JonA

The considerations we have mistaken before include accidentally mounting the mecanum wheels in X and not O configuration and balancing and maintaining the weight/downward force on each of the wheels.

This is something that we had trouble with the first time we used holonomic wheels also. Be careful that viewed from below your robot the rollers on your wheels form an O and not an X.

[Jogo]

Let me just try to clear this up for me and others...the rollers should form an "X" from top-view and an "O" when looking at it from below?

[pfreivald]

No, the rollers should form an O either way.

[Todd]

Originally Posted by pfreivald

No, the rollers should form an O either way.

I'm not looking at a holonomic robot right now, but I'm pretty sure that the rollers should form an O from below and an X from above.

As described here:
http://www.chiefdelphi.com/forums/sh...ad.php?t=80962

EDIT: With mecanum wheels at least, mounted parallel with the drive chassis. Omniwheels are another story.

[GearsOfFury]

Originally Posted by pfreivald

If I may ask, where did you mount your encoders on the p80?

Peter - Last year, BaneBots sold a kit, EN-G0561-KT, that consisted of an optical digital encoder that could be mounted directly (glued) to the output shaft of the gearbox, with a neat plastic cover and mounting kit. It doesn't appear that they offer these any longer on their website, though. I believe they were US Digital encoders, though, so the BaneBots folks may still be able to help you locate some sets.

[pfreivald]

Originally Posted by GearsOfFury

Peter - Last year, BaneBots sold a kit, EN-G0561-KT, that consisted of an optical digital encoder that could be mounted directly (glued) to the output shaft of the gearbox, with a neat plastic cover and mounting kit. It doesn't appear that they offer these any longer on their website, though. I believe they were US Digital encoders, though, so the BaneBots folks may still be able to help you locate some sets.

Thanks for that... Given BB's inability to ship anything even vaguely on time (including non-P60 stuff that wasn't notified as having any kind of delay), I think we'll figure out something for ourselves!

[lcoreyl]

Originally Posted by Todd

I'm not looking at a holonomic robot right now, but I'm pretty sure that the rollers should form an O from below and an X from above.

I am looking at one, and you are correct.
Bird eye view = X , Worm eye view= O