[GeeTwo]

I put together a lesson on drive systems for our (boreal) summer 2014 "robocamp". Trying to classify drives, I came up with something like:

• Skid-steer/tank (2n+4 wheels, drop center when n>0, optional shifter)
• Linkage drives
  • Two-wheel steering (automotive style, rarely if ever seen in FRC, but I wanted to cover it in the camp if only to explain why it is rarely used.)
  • Crab drive (all wheels drive same direction and speed)
  • X drive (I made up this name, but it has 4 wheels, left-rear and right-front rotate together and mirror left-front and right-rear)
  • Fire truck steering (independent 2-wheel steering on front and rear wheels, again rarely used)
• Holonomic wheel drives (I focused here on the wheels with rollers, not whether it was truly holonomic)
  • Omni tank (a 4-wheel skid steer with omni wheels)
  • H-drive (omni tank plus a transverse-mounted strafe wheel)
  • Killough (that is 4 omni wheels in a diamond configuration, not Killough's drive)
  • Mecanum
  • Kiwi (3 omni wheels whose axle lines cross at the CoG, a lot closer to Killough's drive)
• Swerve drives (I described 3 and 4 wheel setups, and explained that other configurations were possible)
• Articulated drives
  • Holonomic wheel hybrids
    • Octanum (includes butterfly and grasshopper)
    • Nonanum
  • Crab/lobster (dual skid/steer - alternate drive is transverse to main drive)
  • Articulated shifter (different size wheels or gear ratios on different drive wheels)
  • Ladder drive (as shown above, though I did not include it this past summer, but will add this year)

I did not include a monobot, or what I've personally called a "dizzy drive" (crab with a big steerable lazy susan for the "upper robot"). I'm sure there are other possibilities.