Re: 2015: Year of the Mecanum
 

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

Re: 2015: Year of the Mecanum
 

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

Re: 2015: Year of the Mecanum
 

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

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

Re: 2015: Year of the Mecanum
 

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?

Re: 2015: Year of the Mecanum
 

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

Re: 2015: Year of the Mecanum
 

I've been doing this too long and I'm starting to get confused. 2010 and 2011 is what I meant to say there.

Re: 2015: Year of the Mecanum
 

not necessarily mecanum but a maneuverable chassis over a power chassie we would rather have a drop center then mecanum

Re: 2015: Year of the Mecanum
 

We thought the exact same thing, after spending all of our off-season saying "well we're almost certainly doing tank drive, but if the game really wants something else..."

Our only experience with mecanum is with an off-season project, which had trouble going straight, we think because of wonky weight distribution. The programming was easy though: WPILib has a straightforward mecanum-drive function in the DriveTrain class.

Re: 2015: Year of the Mecanum
 

My team is also thinking of using mecnum drive. we even have an old robot from logamotion that used mecnum we are able to drive

Re: 2015: Year of the Mecanum
 

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.

Re: 2015: Year of the Mecanum
 

Weight distribution is only one of many factors which can cause unsatisfactory mecanum performance.

Here are some others:

• too much roller axial free play
  
  
• too much roller spinning friction
  
  
• wheel alignment (toe-in¹, camber¹, and axial offset²)
  
  
• excessive gearbox friction (improper assembly and/or lubrication)
  
  
• chain (or belt) too tight or not properly lubricated
  
  
• warped frame
  
  
• frame too rigid
  
  
• motor manufacturing tolerances
  
  
• motor controller calibration

¹Toe-in and/or camber of a wheel causes the wheel sprocket (or pulley) to be non-coplanar with the driving sprocket (or pulley), and thus contributes to friction between the chain (or belt) and the sprocket (or pulley). Toe-in also causes scrubbing friction with the floor surface.

²"wheel axial offset" in this context means that the wheel sprocket (or pulley) is axially offset from the plane of the driving sprocket (or pulley), causing the chain (or belt) to be non-coplanar, thus creating additional friction between the chain (or belt) and the sprockets (or pulleys).

Re: 2015: Year of the Mecanum
 

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

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

Re: 2015: Year of the Mecanum
 

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)

Re: 2015: Year of the Mecanum
 

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?

Re: 2015: Year of the Mecanum
 

Thanks! This looks very helpful...and is also pretty intimidating, although I imagine a lot of those factors apply to any drive train one might make.