pic: drive base idea

[IKE]

Originally Posted by Ryan Dognaux

Maybe not on all 4 corners though. Some teams have had problems in the past (us, for example) with controlling our robot by having a six wheel drive with 4 omni's. 2 omni's would probably be ideal, either on the front or in opposite corners. I'd also suggest powering at least the rear part of your drive, throw a sprocket and chain on that bad boy and you'd be good to go.

This guy brings up some good points. One other thing to keep in mind is if it is a flat game or not. Omni's on both ends weren't terribly freindly for climbing ramps (06, 07). Also if only the middle wheels are powered, it is really easy to get the robot stuck if the front or rear gets propped up a little. Many center only powered robots experienced this phenomenom this year with the bumps created by the inner wall supports (08).
As the drove over the bump it lifted the inside drive wheel off the ground and the machine then swerved directly into the wall. From the stands it looked like poor driving. In reality it was just a little vehicle dynamics issue.

I have another thread going on 6WD dynamics. There is a good link to a paper that explains making your robot turn. My recommendation would be power to at least 4 wheels or have your powered wheels at 1 end of the chassis. This brings a whole new set of dynamics issues though (whip oversteer).