2015: Year of the Mecanum

[Jalerre]

For those talking about driving over the bumps, I do believe that is prohibited. Don't quote me on this but I think it says so somewhere in the manual. Their primary only purpose is as a scoring platform so you don't need to worry about how mecanums are going to get over the bumps.

In regards to programming mecanums, I can say from experience that it is really easy. Our team has used them for the past 3 years. Both Java and C++ (I can't speak for Labview) have methods for programming a mecanum drive (2 methods in fact, at least in the 2014 library). Just plug in your parameters and that's all there is to it.

Finally, though I didn't agree with my team in the past about a mecanum drive train, this year I can really see the advantages. Because there won't be too much robot-to-robot interaction you won't have to worry about pushing power or traction. Also strafing will be really useful when you need to line up to stack the totes and recycling bins.

[nicholsjj]

The code in labview is a canned VI. The only problem that I have had to help teams with is many younger teams make the rotation the throttle axis. Most of the time I have them switch to a button switch statement for turning and it works out fine, some still like other axis turning methods and it can be worked through with the Get axis. Our team has decided to use Mecanum since the no defense is in play and we might try to go for the stack in auto. Mecanum will work out nicely for strafing left or right and picking up as long as you use a gyro for drift. The only initial issues we are concerned with is the frame spacing for the totes and going over the scoring platforms. We think 8" HD's will be fine enough to prototype though.

[Ether]

Originally Posted by Jalerre

For those talking about driving over the bumps, I do believe that is prohibited.

The game reveal video at 1:13 shows a bot driving over the platform.

[jtrv]

Originally Posted by Ether

The game reveal video at 1:13 shows a bot driving over the platform.

He might have been talking about the middle platform, but yes, the scoring platforms can be crossed.

[Ether]

Originally Posted by jtrv

He might have been talking about the middle platform

In the given context, that wouldn't make sense.

Also note that the middle is called a step, not a platform.

[Jalerre]

Originally Posted by Ether

The game reveal video at 1:13 shows a bot driving over the platform.

I didn't see it in the manual anywhere that's just the conclusion that our team had come to. (I didn't try to confirm it I just trusted them)

[craigboez]

If you have 3 rollers on the carpet and one on the hdpe, does the coefficient of friction come into play? I assume as long as you don't break traction on any of the wheels you can effectively transmit force vectors to the ground?

[theCADguy]

Originally Posted by Jalerre

For those talking about driving over the bumps, I do believe that is prohibited.

I believe that you are thinking of the step in the middle. You can traverse the scoring zones, however.

Also, quick question:
Can a mechanum drive be set up where the length of the drive train is greater than the width, or does it require a square wheel configuration?

[StephenNutt]

Originally Posted by theCADguy

Also, quick question:
Can a mechanum drive be set up where the length of the drive train is greater than the width, or does it require a square configuration?

You can set it up with any aspect ratio, square, long or short (within reason)

[Kevin Sevcik]

Originally Posted by StephenNutt

You can set it up with any aspect ratio, square, long or short (within reason)

However, the farther you get from a square configuration, the more scrub you'll get when turning in place. Also, not square configs mean the wrong mecanum layout will make your robot turn backwards. Heh.

[Ether]

Originally Posted by Kevin Sevcik

However, the farther you get from a square configuration, the more scrub you'll get when turning in place.

For a mec, the inverse kinematics are the same¹ as long as it's rectangular.

¹ignoring roller friction, axial free play, and carpet compliance

[Pollux]

There's nothing in the manual about not driving over the scoring platforms. In fact, it makes sense that many robots would have to drive on them in order to deposit their payloads.