View Single Post
Old 08-27-2015, 08:06 AM   #1892 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
Posts: 3,832

Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
Thanks: 1,368
Thanked 1,202 Times in 765 Posts
My thinking is that KP-ID 2000 is too big. Notice the first graph of Kp = 2000, Ki = 0, the error VERY QUICKLY goes to zero, but then zooms past and slowly goes to zero from the negative side. That overshoot of zero means Kp is too aggressive. My understanding is, when you double the voltage with PI loop tuning, that you have to cut Kp and Ki in half to get the same response time. And with a different, very large motor, maybe the current can change very fast due to very low resistance in the 3 stator coils? Try this:

Kp = 100 Ki = 0
Kp = 200 Ki = 0
Kp = 300 Ki = 0
And see if you get ZERO overshoot, meaning the error numbers don't zoom from + to - like this sample:

If you see it go from + to -, that's a sign that your Kp (or Ki or both) number is too big. We may have to increase the resolution of Kp and Ki in the software too. Your motor is a very interesting test case. I've never tried tuning the loop on such a big AC motor.
kits and boards
  Reply With Quote
The Following User Says Thank You to MPaulHolmes For This Useful Post:
thingstodo (08-27-2015)