Getting the bot to go straight?

[JamesTerm]

"
The old Drill Motors were biased to run faster forwards than in reverse
"

We found a similar symptom to happen with our robot and I believe we are using CIM. Basically when appling equal voltage say 0.08 on both motors only one side would run while the other did not. I've applied a software solution that removes the "dead-zone" like what you can do for joysticks, and then linear interpolate the rest of the values. With the wheels on drive blocks I can see this appears to work, but I have not yet tested on the ground. I feel confident that a software solution could work even if it requires an exhaustive attempt to plot a graph of several points to obtain the derivative for each side. I think voltage applied to the motors only are linear, but due to the chains and other static friction it makes it appear more logrithmic. Unfortunately one of our encoders is still defected (returns NAN), and we are all too mechanically challenged to fix it. So I am hoping for a miracle with tweaking the voltage distribution (or hope to get team to install a gyro).

I've added more details (and videos) on my blog here:
http://www.termstech.com/articles/