I'm running a custom STM32F446-based design with a 7-pole 750kv motor, operating at 16V. The "kv" command gives me 5100, which is pretty much exactly right.
When starting the motor from stop, it usually works fine -- but occasionally seems to go into a stable "wrong direction" mode, where a lot of power is used to barely spin the motor. Here's an example: (command of 0.1 duty cycle followed by brake several times. Last time it does the bad thing)
- Screenshot from 2017-06-02 20_25_59.png (149.71 KiB) Viewed 1452 times
- Screenshot from 2017-06-02 20_25_56.png (171.4 KiB) Viewed 1452 times
(Note that in reality in the last run it's actually spinning in the opposite direction, while making DRDRDRDR sounds).
This mode happens *always* when trying to start from still in RPM mode with high enough gains. So it seems to have to do with how spinup works before there is a reliable BEMF signal.
Any hints? Would be hugely appreciated!!