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FOC works, but BLDC doesnt.

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Last seen: 4 weeks 1 day ago
Joined: 2019-06-30 21:07
Posts: 4
FOC works, but BLDC doesnt.


I decided to build my own high powered VESC, that is based on VESC and is really similar to this project (same current HAL sensors, fets, isolation):
But here I am now:
Things seem to work in FOC mode, passes detection, numbers are reasonable, spins up small and big motors really good with and without HAL sensors, doesnt get hot, decent performance with different loads and voltages, looks great!, But whenever I try BLDC mode motor just jerks around and doesnt even pass detection. I have managed to get motor "spinning" in detection with some odd current values,but its far from smooth rolling. I have probed gate signals, phase voltages, currents, etc, everything looks reasonable. Also tried different VESC firmware versions.

Why do I even bother with BLDC? Well, quite often when accelerating/braking from freewheeling in FOC mode it seems like ESC loses sync with motor. It causes ABS overcurrent fault when braking. Using sampled data I see that current sinusoidally spikes real high 400+A with large motor
When accelerating it produces large jump at first and I can see in graphs that current goes negative for brief second. 
It happens with and without HAL sensors and I think it has something to do with that motor is not able to work properly in BLDC mode either.

If anybody has any idea where should I continue debugging I would really appreciate the help as I dont know enough how different motor controlling algorithms work and quess the location of the motor.
Im uploading pics of graphs later.