Robots not under driver control- does it happen- do you determine why?

[Alan Anderson]

At a pre-ship scrimmage, our robot would occasionally start spinning in circles or take off at high speed in reverse. This would happen with nobody touching the driver joysticks. The program was definitely using only those joysticks to control the drive motors. Some of the team believed it was a communication issue, but I couldn't see any evidence of that kind of problem.

It took us most of the day to track down a bug in our rate limiting code. It was intended to keep the robot from accelerating backwards quickly so a chain tensioner wouldn't be overstressed. The bug was being triggering whenever a joystick went just barely outside the deadband in reverse. We spent a few minutes puzzling over the code, first trying to figure out how it was broken, then trying to figure out how we had intended for it to work in the first place. Finally we just threw it out and rewrote what it should have been originally.