[DanL]

Hmm. That does make sense. Two questions though:

I once looked into racecar launch control systems. The things I read said the fastest launch speeds are achieved by allowing about a 10% slip. Is there a basic-physics explanation for this, or is it due to the non-linear characteristics of rubber tires?

Second, say you mount one pair of wheels inline with the robot/trailer CoM so that the force produced is tangent to the path traced (well, assuming no linear net force). Do /those/ wheels slip in a skid-steering configuration (in the ideal case)? If not, would it be beneficial to have an angular TCS if you built your robot like this?

[edit] By CoM, I mean axis of rotation. If you put a pair of powered wheels in line with the axis of rotation, the path that they would trace would be a circle (with the wheel's direction of movement tangent to said circle). Therefore, the ideal turn would be such that there was no slippage on these wheels, and you could theoretically program some kind of rotational traction control system. I don't quite remember how to figure out the axis of rotation given a few force vectors on a rigid body, though. Also, this would only be the case if the wheels were in line with the axis of rotation... once you get off that axis, the wheels by definition need to slip, and you're in the useless case which rwagner described...