Need higher resolution speed measurement in FOC code.

[BTrem.1]

In my sensorless application driving a BLDC I need the best resolution possible.

I set the SPEED_UNIT to _001Hz but the feedback from the SPD_GetAvrgMecSpeedUnit procedure still seems to be in units rounded to 6.

For example I can read 3059 and 3064 but nothing in between. I'm running a 6 pole-pair motor at nominally 30.5Hz and my requirement for speed variation is <2us p-p jitter. I'm finding it quite challenging 😉

I'm using a STM32G431 48-pin device with a STSPIN233 using 5V on a custom board. My start current peak is about 700mA and my run current is typically 35mA peak.

For my speed feedback in procedure STC_CalcTorqueReference is SPD_GetAvrgMecSpeedUnit the correct procedure to use to get measured speed?

Also, I can not find the source code that SPD_GetAvrgMecSpeedUnit uses to calculate the average, I think it is procedure STO_PLL_CalcAvrgMecSpeedUnit. Is that available?

Thank you for consideration of my problem. All suggestions welcomed.

[Laurent Ca...]

Dear @BTrem.1​ 

Are you sure about your example?

Indeed, 3064 is not a multiple of 6 but of 8.

Best regards

[BTrem.1]

I need to withdraw my question. I collected more data and plotted a histogram on over 1000 samples taken at 1ms sample rate. The table is shown below

I think my problem is if I sample at the motor electrical rate of 5ms (6 pole pair) I get an aliasing effect and only get sample values 3328 and 3334. Is there any documentation on the procedure SPD_GetAvrgMecSpeedUnit ? It simply returns a pointer pHandle->hAvrMecSpeedUnit. I cannot find where this is updated and I can not find any information on the buffersize it is averaged in.

Thanks,

Brian

Brian

[Laurent Ca...]

Dear STM32 Motor Control Community members

You follow the following thread about SPD_GetAvrgMecSpeedUnit in this new question: https://community.st.com/s/question/0D53W00000xsTlzSAE .

Best regards