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Original question:

MCF8316A: -101

MCF8316A: How to set the configurations to run the MPET right?

yao eddie
Prodigy 50 points
Part Number: MCF8316A

Hi,

There days I am trying to run the MPET to get the MOTOR_R/L/BEMF CONST, there are something I could not understand.

The OL_ILIMIT_CONFIG was set to 0, the OL_ILIMIT was set to 8A, the faults of E2 was always 80080000, and always could get the BEMF.

Based on the sllu335a.pdf, I tried a lot of different combinations, between the MPET_OPEN_LOOP_CURRENT_REF, the MPET_OPEN_LOOP_SPEED_RE and the MPET_OPEN_LOOP_SLEW_RATE, it always failed. 

For example, the MPET_OPEN_LOOP_CURRENT_REF was set from 1A to 4A, the MPET_OPEN_LOOP_SPEED_RE was set from 15% to 50%, and the MPET_OPEN_LOOP_SLEW_RATE was set fromr 1hz/s to 20hz/s, always faild. I really don't know how to tried now, could you pleae help me analyze it and give me some suggestions? 

Hope to get your replay soon!!

regards,

Eddie

  • 0
    Prodigy 50 points

    sorry,  Correct it at "always could get the BEMF". always could not get the BEMF.

  • 0 in reply to yao eddie
    TI__Genius 9220 points

    Hi Eddie,

    When running MPET BEMF measurement, the device will spin up the motor using open loop (blind) commutation.

    • The MPET open loop current needs to be set high enough to overcome the initial rotor inertia/friction but not too strong to cause rotor to jerk/wobble too much
    • The MPET open loop slew rate / acceleration needs to be slow enough to ensure the rotor is able to keep up with the open loop commutation but too slow may cause some rotors to not spin up smoothly in the beginning.
    • The MPET open loop speed threshold needs to be set high enough so that the motor generates sufficient BEMF at the configured threshold percentage of MAX_SPEED.

    I saw the other post you made about getting KP and KI after MPET, so were you able to complete MPET successfully?

    Regards,
    Eric C.

  • 0 in reply to Eric Chen
    Prodigy 50 points

    yes， IT is done, but there were some other problems, I will ask with other question.

    Thank you so much~

  • 0 in reply to yao eddie
    TI__Genius 9220 points

    Hi Eddie,

    Thanks. I'm working on your other thread and will provide an update before end of today.

    Regards,
    Eric C.