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Erratic behavior during lab2c when setting RES_EST_CURRENT too low

Scott Phan49
Prodigy 155 points

Other Parts Discussed in Thread: BOOSTXL-DRV8301

Hi, I had been running the labs on a smaller hard drive motor for testing with default system parameters starting with the motor ID lab2. Then I'd switched to a large Turnigy motor which has very low inductance but high speed and power (max power rating at 590W; max volt. at 15V) with the motor ID in lab2c. I had missed the user.h param, RES_EST_CURRENT, which led to the motor not spinning. I later corrected RES_EST_CURRENT which is all fine and it ID's and spins but what I'm worried about is when I had it at 1.0A (too low), towards the end of the run_identify it overloaded the power supply and produced a loud screech before run_identify switch to 0 (w/o error).

I'm wondering what would be causing this as I plan to hook up a much larger motor to the launchpad and don't want the same erratic power jump happening during the motor ID should I set the RES_EST_CURRENT too low.

I'm using the BoostXL-DRV8301 and Launchpad F28027F.

Thanks,

Scott

  • 0
    TI__Guru** 119680 points
    when doing motor ID, if the motor doesn't start spinning during RampUp and continue to spin for the rest of the ID process the ID process should be canceled. Ideally we would have added this check to the ID process, but we didn't.

    What is happening is since the motor is not spinning an incorrect inductance is calculated which is then used to set the tuning of the current controllers as the loop is closed. These gains are too high and the current controller squawks (and in your case causes an over current situation).
  • 0 in reply to ChrisClearman
    Prodigy 155 points
    That makes sense, thanks.