Distance of travel while using mecanum wheels

[Onederful]

How do you calculate the distance the robot will travel relative to the rotations of the mecanum wheels while strafing, going forward, and a diagonal?

[Duncan Macdonald]

If I were in a time crunch with an assembled robot in front of me I would drive a known number of rotations and then measure the distance traveled.

[jspatz1]

I'll take the "going forward" part: Same as any normal wheel.

OK, somebody else take the others.

(Seriously, I agree with the "measure it" suggestion. Better than any calculation or guess.)

[Chexposito]

If it were me, i would use an accelerometer and gyro, to much slip in mecanums to be able to be reliable especially when you are moving in a non-forward direction

[AdamHeard]

If you truly want reliable data here, you might want small, lightly loaded, unpowered wheels on the ground that are hooked to encoders.

Vex omniwheels work great for this, you can measure X with one and Y with the other.

[Alex.Norton]

As already stated, forward and backward is easy, it just acts like any other wheel here. As for strafing, this will depend on the angle of the rollers on the wheel, most will be 45 degrees, but I've seen other angles. If the rollers are set at 45 degrees then in the best case, the robot will strafe at the same rate it moves forward or backwards. Of course there will be some scrubbing losses, so it won't be optimal, but that is true or forward and reverse as well.

[JesseK]

As already stated, forward and backward is easy, it just acts like any other wheel here. As for strafing, this will depend on the angle of the rollers on the wheel, most will be 45 degrees, but I've seen other angles. If the rollers are set at 45 degrees then in the best case, the robot will strafe at the same rate it moves forward or backwards. Of course there will be some scrubbing losses, so it won't be optimal, but that is true or forward and reverse as well.
^ I can confirm this post. We did our testing in early 2010.

[lon.bushweiler]

Team 93 is using a small omni drag wheel with encoder that is pressed to the ground with surgical tubing to determine exact distance travelled in autonomous. The gyro is also used to ensure that the robot stays properly aligned with the scoring rack.