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InstaSPIN for a low-speed high-torque motor

Seok Joo Jang
Prodigy 230 points
Other Parts Discussed in Thread: DRV8312

Hello,

I tried to run a very slow motor with InstaSPIN control. But there are some restrictions with the parameters in user.h and I get errors from USER_getErrorCode(&gUserParams) function.

The motor is a 125V 0.42A 13Hz pm motor with 4 pole pairs.

Should I change some numbers in user.h which have 'do not change' comment? Or is there any workaround?

Thank you!

  • 0
    TI__Guru** 118790 points

    which error are you getting?

    13 Hz is the maximum speed?

    Which HW are you using?  You will need to scale your current and voltage readings to maximize resolution for best results....probably will have to run RsOnline all of the time as well.

    But I'm not sure if sensorless observer techniques will be the best solution for an application like this.  You may want to think about a high frequency injection technique if the motor is salient....or stick with using sensors.

     

  • 0 in reply to ChrisClearman
    Prodigy 230 points

    Hell Chris,

    Thank you for your help again.

    Yes, the rated frequency of the motor is 13 Hz.

    The error code is USER_ErrorCode_RoverL_estFreq_Hz_High. I used the DRV8312 and HVMTR. Both cases show the same error message.

    As you mentioned, I will use the encoder sensor. But I did not come to the encoder lab (lab12?) yet.

  • 0 in reply to Seok Joo Jang
    TI__Guru** 118790 points

    Just put the FULL_SCALE_FREQ to (200.0) and the error should go away. 

    However, for Flux ID what Freq are you trying to use?  

    I'd try 8 Hz

    And then you need to set ZERO_SPEED_LIMIT to (2.0/200.0)

    Still not sure it will work though....

  • 0 in reply to ChrisClearman
    Prodigy 230 points

    I set FULL_SCALE_FREQ to (200) and USER_MOTOR_FLUX_EST_FREQ_Hz to (3).

    Then the HVMTR drive with proj_lab02a identified the resistance and inductances.

    I will move on to the sensored control.

    Thank you.

  • 0 in reply to Seok Joo Jang
    TI__Guru** 118790 points

    what values for Rs, Ls, and Flux were identified?

    Did you try running it to see how it behaved? 

  • 0 in reply to ChrisClearman
    Prodigy 230 points

    Here are the result.

    Rs = 80.69006

    Ld = Lq = 0.5219215

    Flux_VpHz = 4.837737

    I measured the line-to-line resistance, which showed 159 Ohm. Rs looks good. I did not check the other numbers.

    For safety reason, I applied DC 60V from a lab power supply. The motor ran smoothly up to 50 rpm. The higher speed was not achievable probably because the DC voltage is too low.

  • 0 in reply to Seok Joo Jang
    TI__Guru** 118790 points

    Very cool. What HW did you say this was?

    How low could you run with ForceAngle DISABLED?  I would expect <1 Hz with a flux this large.