paper: 4 CIM versus 6 CIM theoretical calculations

[MichaelBick]

In practice, my guess is that you can draw way more current than 200 amps. Just based off of my team's 2016 drivetrain, which was 4 CIM with no voltage ramping, we experienced no brownouts even going from full forwards throttle to full backwards throttle. If we assume that our robot was traction limited below 40% of our max speed (a conservative assumption), we were drawing over 300 amps max.

Another cool aspect to current limiting is changing the limits in real-time based on each subsystem's need. For example, in a 4 CIM "hard right" turn -- 0% power on the right drive side, 100% on the left -- you may only be drawing 50% of what the battery is able to provide. If you have 1.5 or 2 times the power and current limit, you can double the current limit on the left side so that you fully utilize the battery. This same idea can be used to change the current limits to better follow a motion profile or prioritize superstructure motions.

One last important item to keep in mind is the main breaker. A high power drivetrain with a current limit pulls the maximum current for more time than an equivalent lower power drivetrain. Because the main breaker is heat triggered, it is sensitive to prolonged periods over the 120 amp breaker limit, and therefore high power drivetrains are more likely to blackout than lower power drivetrains.

Given that the talon SRX now supports current PID, a lot of doors have been opened for teams to find performance improvements with current limiting.