[JDNovak]

Team 16 has used CAN since 2010. We started with the 2CAN from the beginning and ran 10 Jaguars the first year and 11 Jaguars in 2011 and this year. The biggest issue the first two years was an initialization problem at boot up that was hard to detect but would render the robot motionless at the start of the match. This risk caused us to convert to PWMs at the end of last season.

This year we started again with CAN intent on finding the issue and solving it rather than avoiding it. We haven't had the problem with this year's firmware and CAN driver. We did have problems with the original 2CAN due to static but we were able to overcome that until we could get the redesigned 2CAN just before the start of the season.

There are tradeoffs with every system. Every time we build another robot we have cable issues until all marginal ones are found and replaced. After that we have had very little trouble. As several have alluded to, a cable problem usually takes the whole system down due to daisy chaning and failed termination. I intend to create a bus system that reduces this weakness similar to the ones referred to above. The 2CAN web page is invaluable in finding problems quickly. It can even be monitored through the router while driving to see motor loading and intermittant problems.

One side issue I would like point out is the Jaguar overcurrent protection vs Victors. I have had a few motors fail in the last year and a couple with very low resistance. The Jaguars shut down fast enough to keep the battery voltage above the reset point of the Crio and D-Link. I have heard of shorted motors on victors in at least a couple of cases that left robots dead while the system rebooted. Sometimes the quick overcurrent protection is worth something. We have had no problem with overcurrent shutdown on properly geared systems.

One of the reasons we continue to come back to CAN is the inherent current monitoring on every motor. One use is to protect motors in parallel. Our winch this year uses worm gearboxes in parallel to eliminate backdriving. if one motor doesn't drive the other is stalled and fails quickly. current monitoring allowed shutdown fast enough to avoid this problem.

As for PID control on board. the testing we have done has worked well but we always wind up back in the Crio because of lack of features in the Jaguar. Syncing two motors is a big issue. If there were some filtering options and the configuration was non-volitile I think we would be using it.

It will be interesting to see what transpires with TI backing out of manufacturing Jaguars but if we have to go back to PWM I'll be dissapointed.

My opinion is that a lot of the challenge of robot design is in finding how much technology you can incorporate into your design without making it the weak link. This about science and technology, isn't it?