[JesseK]

I'm not sure about how the timing of this presentation will fit into my own schedule, so I'll post a story here.

Thursday, April 7, 2011: VCU Day 1
We put the bot on the field after readjusting the chain runs for reliability after a demoralizing performance in DC. In our first practice match, the robot did a very dangerous robot dance -- the lift was up to 10', the bot would go-turn-stop-go-turn-stop and do so very violently while doing a sweeping left turn (tough to describe...). It only progressed worse as autonomous continued due to the side-to-side rocking. Finally the bot stopped due to an internal timer (9s) and the lift came back down. We were pretty sure the welds on the lift would pop since the entire base of the lift was twisting as this went on. We were lucky. On the plus side the chains didn't pop off during that entire episode, reassuring us that they were fine for the rest of VCU, and we're now 100% sure our c.g. is "low enough".

It turns out that the double-throw pneumatic valve wiring to the shifting transmission cylinders went bad while we were fiddling with something else. One side of the drive train was stuck in high gear while the other side was stuck in low gear. The 'drive straight' 'P' on the gyro PID wasn't set nearly aggressively enough, so the software couldn't compensate for the 2.56:1 ratio difference in mechanical speed that resulted between the left side and the right side. 100% PWM signal to both sides resulted in very different speeds. Later we tuned the gyro's PID and ran 11 consecutive perfect autonomous modes.

It's a good case for simulations that test error conditions or mechanical failures on the bot.