In the course of testing, we found that the difference between the static and dynamic coefficients of friction between any given rover wheel and the regolith was about 20%. However, the difference between clean and dirty (covered with FRP dust) wheels was on the order of 40-50%. I believe that this accounts for some of the discrepancies between the published CoFs and values that multiple teams found empirically in the first week of build.
So while we had some sort of software traction control implemented at all three of our events this season, it was our "mechanical" traction control that helped us the most. Each of our four drive wheels had a paintbrush mounted against it at the top of its rotation. These brushes did a superb job of keeping our wheels clean during and in between matches, and spared us the chore of having to diligently clean our wheels by hand (though we did need to periodically clean out the brushes - you wouldn't believe how much dust they would accumulate). As a result, we were typically a very slippery target for opposing robots (look at our DPR stats this season, although in Philly a couple of problems made us a sitting duck once or twice). Multiple other teams commented on our ability to break out of pins, and it was only when it was 2-on-1 that we were really immobilized.
However, it is interesting to note that our choice of wheelbase meant that despite our tractive advantages, we weren't a very good pinning bot. We were a "skinny" bot because of dimensions of our scoring system, and we had a 4WD setup on a shortened wheelbase towards the rear of our machine.
Top view:
Code:
^ this is front
^
_____
| |
|w w|
|w w|
w = wheel
As a result, if we were pinning another bot, it was easy to turn us because of the distance between our robot front and our wheels (our chasis acted like a long lever). Thus our pins were usually not hard to get out of.
Lastly, we found that TOO much traction control was not always a good thing. Our initial software (used in San Diego and Philadelphia) fought to keep the bot on course and slip-free, making drifting and the effective use of the trailer's momentum to quickly turn more difficult. In Atlanta, we toned it back just to acceleration limiting, and our driver responded with our best robot performance (despite the outcome) of the year.