Traction Control for a Turning Tank-Drive

[DanL]

Originally Posted by Rick Wagner

Your thinking on that seems sound, but as you can't "track" (no slippage condition) and turn, by definition,

What exactly do you mean by this? I don't quite understand. Can you elaborate?

And I completely agree with you regarding usage of traction control in a pushing match -- a TCS would probably do the exact opposite of what you want. You definitely need an on/off switch.

[Rick Wagner]

Originally Posted by DanL

What exactly do you mean by this? I don't quite understand. Can you elaborate?

And I completely agree with you regarding usage of traction control in a pushing match -- a TCS would probably do the exact opposite of what you want. You definitely need an on/off switch.

The whole idea behind anti-slip control is that the wheels have a higher coefficient of friction when they are not slipping (they are tracking true), so the robot can accelerate faster and push harder. Any slippage at all and the wheel force drops about 20%. As you will be slipping in turns, by definition with slip steering, you will lose traction anyway and there's really nothing you can do about it. So anti-slip control makes sense only for straight line acceleration and straight ahead pushing.

[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...

[deusex]

i have thought about using the comparative math earlier that looks at the forward momentum and then based on the case, modifies the casestrucutre and ultimately modifies the scaler going to the system

[Burmeister #279]

Right off the bat we started with a 'master' disable switch on the driverstation and a momentary reset/disable button on the joystick, and thus far its been quite valuable in testing differences, as well as the fact that if something goes, say, kablooey [a strictly technical term], it can be both reset temporarily or shut off. using something like this could save your drivers in a dire situation.