• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 80 subscribers
  • Views 520 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Phase Shifting Comparison

Louis Zhu
Expert 1675 points
Other Parts Discussed in Thread: CONTROLSUITE, MOTORWARE

I ported my FOC motor control project from Multi-Axis DMC EVM [R3] (F28035 based) platform to DRV8312EVM RevD (F28069M based) platform (I'm not using InstaSpin FOC features), I had problem in closing current PI control loop.

After looking into phase current waveforms, I found that the phase current phase shifting is much different on the two platforms. From the attached document, you can see that the phase A current leads its voltage about 30 degrees on the old platform, however, the phase A current lags its voltage about 150 degrees on the new platform, which results in the opposite sign of the Iq and Id between the reference and the feedback.

There are no implementation differences in the control laws and FOC algorithms beyond low level drivers, although I noticed that there is a 4.7 uH inductor on each phase (OUT_A/_B/_C) on the new platform, while the old platform does not have such inductors.

I'm out of ideas these days, please help look into this issue. Thank you!

Phase Voltage and Current Phase Shift Comparison.docx
  • 0
    Expert 1675 points

    Can anyone help on my question?

    Chris, you must have some ideas.

    If I did not describe my question clearly enough, please let me know.

    Thanks,

    Louis

  • 0 in reply to Louis Zhu
    TI__Guru 57255 points

    Louis,

    I believe the change is due to the differing opamp stage circuitry on the two boards.  You can find the schematics of the two boards in controlSUITE.

    On the multi-axis kit you will note that the non-grounded shunt input goes into the negative terminal of the opamp.  This opamp and the resistors around it will therefore give a negative gain.

    On the DRV kit the non-grounded shunt input goes into the positive terminal of the opamp.  This will then lead to a positive gain. 

    The difference in the sign of the gains leads to a 180 degree difference between the two (which appears to be what you are seeing).

    Hopefully this helps!


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Expert 1675 points

    That explains why the phase current values are negated in the MotorWare function

    DRV_readAdcData().

    Who said that software engineers don't need to know hardware?

    Thank you very much!