Modest request for next Jaguar firmware

[Levansic]

Like other teams using Jaguars on the CANbus, we saw a few areas of operation that need to be improved. As a mentor, I can see why quite a few teams are leery of the results. Quite often, the deficiencies we saw, and others have commented on, are not really fair to pin on the Jaguar, since it is more likely that the Jaguars expose problems that the cRIO's longer time slices tend to hide.

Instead of complaining about the Jaguars PID implementation, I think it would be more constructive to offer suggestions for incremental fixes that would make it easier to recommend closed-loop on the Jaguars with confidence. In this spirit, I'll offer the first suggestions:

1. For speed control; turn off the output if the commanded speed is 0, and the brake is set to coast.
   
   Rationale - We send 0 speed commands initially to our drive motors, as part of the initialization. When the robot is suspended (to keep the wheels off of the ground), there is enough backlash in the typical FRC gearboxes that the encoders will register small movements. The PID then attempts to counter the perceived speed, causing a thrashing of the wheels and gears, when a 0 rpm speed is commanded. Turning off the output for this case is safe.
   
   
2. Offer a simple filter (e.g. moving average of last n readings) for the encoder feedback. This could be on all the time with a user-settable range like 0 < n < 32. Unfiltered would correspond to n = 1, and lag and smoothness increases from there.
   
   Rationale - It appears that the Jaguars are too responsive to the noise in the encoder signal. The speed of the control loop is far faster than the motors that will be hooked up, so the minor lag of grabbing 5-15 encoder readings would not be noticed.