This is kinda off from your discussion, but when you started taking about feedback - that were we come in Team 670 has developed a close-loop steering mechanism that allowed our robot to have semi-real time feedback from our robot. I'll try and post a pic or it soon but here's the rundown.
We used the new window motor along with a steel plate attached to the gears on the motor. The plate has a slit down the center of it an as the motor turns from side-to-side it moves a bolt attached to a rack n' pinion. Directly over the motor output gear is a rubber stopper, which hold the end of a 0-255 Potentiometer. Our operator mechanism was a wheel and stick system, when the stick was moved in the X direction the robot would move forward or reverse.
The wheel when turned left or right would generate a negative feedback loop and move the motor in the correct direction. If you have anymore questions on the closed negative feedback loop steering system. Email me at
chrisccts@yahoo.com