Failed attempt to explain JAG linearity

[Al Skierkiewicz]

Chris,
During the time that valid drive signals are being converted to output, the brake and coast mode is not enabled. The selected mode only takes place when the input PWM goes to 127 or neutral value. Think about that time when the the throttle is just off the center position. The motor gets a very short pulse of output voltage. If the controller was in the brake mode during the off period, the motor would not turn very much. That is obviously not the case.
As an off season project for a team, I would like to see the test results of CIM motor linearity plotted for different loads. It would need to compare the linearity of the CIM at the max efficiency point, and several points on both sides as the motor approaches free speed and stall.
When teams report trouble tuning PID loops, I always wonder what else might be at play. As you know, things like non-linear frictional loss, gear backlash, motor bias, production variances in motors, misalignment of drive train shafts, minimum resolution on sensors and chain wear are all things that contribute to problems with achieving desired response.