PID code questions

[Kevin Watson]

Originally Posted by Dave Flowerday

The effect seen at kickoff was the loop overshooting. This can come from either too large of an integral term or too large of a proportional term or some combination of the two. The problem with PID loops is that it can be tricky to get the behavior "just right" such that the loop doesn't oscillate, doesn't overshoot, and has a fast rise time all while dealing with varying external forces. Most likely the problem stemmed from the fact that when Dave kicked the robot, the angular velocity that it encountered was much higher than what the robot was capable of on its own, so the PID loop was not as well tuned for it as when it was driving under its own power.

The proportional gain was set too high. The demo code was finished the evening before the kick-off and we didn't have/spend enough time tuning the 'bot. When we got it tuned to the point where we were (reasonably) confident it wouldn't slam into Dave's ankle, we quit for the evening <grin>.

-Kevin