Hi all!
I've been experiencing a jittery motor. Almost like the position tracked is not accurate and it "skips" one pole. It only happens when with moderate to high requested current at moderate to low speeds. The strangest part is that it only happens when applying torque in one direction (braking while going forwards or reverse accelerating)
Heres a short video demonstrating what I'm talking about: (audio on)
Please ignore the click where the belt skips, I've fixed that already 
but you can clearly hear the jittering.
I have a flipsky 4.12 and a turnigy aerodrive sk3 6374 149kv motor, a combination which I would expect is fairly common. I'm using it in sensorless FOC mode, but I've observed the same problem in BLDC mode.
I have tried every possible setting I thought could be relevant and then some, but I'm open for any suggestions as I'm reaching the point of desperation
I've also tried switching the motor direction and swapping two of the motor leads, and the problem still occurs in the same acceleration direction (from the skateboard perspective), leading me to believe that my hardware has no defects and instead looking at the control side of things.
Any suggestions are welcome and thanks in advance
The 4.12HW is a very old design with only 2 low side shunts and no phase filtering. Don't expect a perfect behavior in sensorless operation, especially close to zero speed. Some cogging is to be expected when using these cheap old controller designs. From what I can see in the video it's not too bad. The short VSS bleeps you can hear are totally normal and are used to track the rotor at low RPM. BLDC is outdated and for the sensorless stuff you should always use FOC.
I want to point out its not just at close to zero speeds, it does also happen at medium speeds. (To be honest I haven't tested that much on high speeds as I'm still a noob :P). I do consider it problematic and a safety concern as it is seriously hampering my ability to break. I have to be quite smooth on the throttle in the problematic direction, anything above the threshold where this starts happening, I suddenly lose 80-90% of braking power and coast for very long distances. I'm essentially limited to 15-20% of throttle in one torque direction.
I am aware that the bleeps are from VSS after I did stop, but you can hear throughout the entire video the oscillating power is what I perceive as it jittering and skipping poles. Thats not me playing with the input, I am holding it at a fixed level.
What confuses me most, and gives me hope that it can be fixed, is that in the other torque direction, it does work perfectly fine. I can floor the throttle to max and it gives me perfect acceleration/braking behavior.
Usually a simple detection is done and things should work. If the controller is doing funny things it might be a HW related issue. The controllers should work the same in both directions.
What is your suggestion, do you have any pointer as to what the culprit might be?
Not sure. This is a question for the Manufacturer. Do you run the latest FW?
I'm on the latest FW that comes bundled with vesc tool, 5.3. It does state that my hardware is 4.10 when it is 4.12, but from what I could find on here, thats not an issue right?
410, 411 and 412 all use the same firmware.