Improving BLDC FOC Sensored (Hall) Startup

[jimkolonis]

Hello all,

What I have:
FRDM-KV31F logic board
FRDM-MC-LVPMSM power supply / motor board
48VDC BLDC motor w/ Hall sensors
MCUXpresso & FreeMASTER project from AN12374

I am a novice at motor control applications. I chose the FRDM-MC-LVPMSM power supply / motor board since it will handle my motor's power requirements (48VDC), whereas the FRDM-MC-LVBLDC handles only up to 24VDC. My nascent understanding of PMSM is: PMSM can include BLDC or BLAC motors, so this hardware choice is acceptable.

For my application, I need to be able to provide high torque to the motor on startup, but I am wanting to use the FOC commutation during medium/high speed to reduce produced torque ripple.

I am able to get the motor running using the FreeMASTER connection and speed control (commanded RPM). However, I am getting a bit of "cogging" during (Sensored) startup, where I observe the rotor toggling between a few hall states. I have attempted tuning this out of the system by adjusting the Sensored position observer bandwidth, but I am not having much luck.

I am not seeing much about the startup tuning process in the AN12374 document. Would anyone have any recommendations for how to reduce the hall state toggling during the startup phase of motion?

I'll attach a few pictures for reference.

Thanks!

[jimkolonis · Accepted solution]

I solved this problem by implementing trapezoidal commutation during the "Startup" run state and used the "Sensored" configuration that causes the position observer to use the Hall Effect rising/falling edges as its input. Keeping the trapezoidal duty cycle below 30% allowed the transition to occur smoothly. This answers my question.

[FelipeGarcia]

Thanks for sharing your solution with the community!

Best regards,

Felipe