[taichichuan]

Team 116 had a mixture of CAN and PWM on this year's robot. Jaguars on the ball guide and shooter motors (one on each side) and Victors to run the wheels due to size constraints and the annoying habit of the Jaguars resetting when the drivers do a full forward to full reverse thing. You could address that with motor ramping, but we wanted to give our drivers the ability to do whatever they felt was necessary to drive the robot on the field.

2010 and 2011 were pretty much all CAN except where there wasn't enough room to mount a Jaguar and a Victor was used. We had a couple of issues in 2011 based on a bad Jaguar firmware release. But, those problems appear to have been addressed with firmware 101.

However, to many, the Jaguars are damaged goods. Problems with aluminum falling into the Jags and shorting them out, problems with resets because of rapid full forward/full backward control movements, their sheer size, the relative ease with which students (and mentors) could reverse wire the input power and toast them and problems with the RJ-12 connectors have all contributed to the perception that the Jaguars are not a good choice. The fact that CAN can only be used for control with a Jaguar means that CAN gets a bad rap as "guilt by association".

I think that TI/FIRST putting the Jaguars out for re-competition is a good thing. The RFP is open enough to support some crucial modifications that have been long needed in the Jaguars. But, given the perception that the Jag are bad, I'm not sure that you'll find any manufacturer who'd be willing to take that project on with a design they didn't control the IP for with special firmware specifically designed for FIRST and in a really limited market like our robotics applications.

The Stellaris micro-controller is an ARM Cortex M3 -- a very stable chip that is similar to the controller used in the VEX control unit. The Stellaris line is very successful for TI with sales going up by a factor of 2x this past year. But, they just can't make any money on the Jaguars. So, this RFP is a way for TI to dump the Jaguar and move on to more lucrative ventures.

For folks that say CAN is unreliable, I ask if you drive a car made in the past 10 years. If so, you've likely got CAN bus. CAN is *very* reliable. But, the implementation that we see in the Jaguar can be prone to problems because of all of the failure modes of the Jaguars themselves.

However, the ability to get better low speed control and the ease of wiring the robot really speak well for the Jaguars in CAN mode. Add to it the closed loop support modes, and I think that CAN is ultimately a winner. We just need a better implementation, so we can put the CAN is unreliable issue to rest. So, I really hope that the RFP process will be successful and we can get a manufacturer for these new motor controllers that will stay with us while they work out the issues with CAN control and we work out the learning curve to be better able to take advantage of the features that CAN brings to the table.

Mike