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InstaSpin FOC DRV8301-69M-KIT Help

Steve Marks1
Prodigy 120 points

Other Parts Discussed in Thread: MOTORWARE

Hello, I have been evaluating an instaSpin FOC DRV8301-69M-KIT for a couple weeks. I have a question about what is used for the base value for the per unit values.

The confusion comes from conflicting documentation. The instaSpin users manual, section 5.1.2 seems to clearly state that the USER_IQ_FULL_SCALE_VOLTAGE_V

USER_IQ_FULL_SCALE_CURRENT_A are used as the base value.

 Howerver the TI wiki clearly states that the TI DMC libraries use max measureable ADC values.

http://processors.wiki.ti.com/index.php?title=TMS320C2000_Motor_Control_Primer#PU_System_Model_and_Base_Values

This is important to understand this because I want to re-scale the board to operate at 12 volt < 10 amp operating range. I have the hardware side figured out, I need to determine what all needs changed in the software.

Additional info:

I understand fixed point math and per unit values.

I'm using "proj_lab02a" that ships with Motorware as the source code to experiment with.

Thanks for any help.

- Steve

  • 0
    TI__Guru** 119680 points

    Steve,

    Please use the MotorWare InstaSPIN documentation and not the TI DMC Libraries. They follow the same philosophy of per unit, but the differences may confuse you.

    The maximum range of input to the ADC pins is set by the hardware circuitry.  The values at the ADC between 0 and 3.3V correspond to the values 0 to 2^12 (4096) by the registers of the ADC The variable USER_ADC_FULL_SCALE_XXXXX is the scaling factor that lets you determine the real world value for any value in the ADC register. [Note that there is also an ADC Bias, an offset value to this register based on the value of the ADC conversion vs. an expected conversion of 0]

    The USER_IQ_FULL_SCALE_XXXX are the values used to normalize into per units for use inside the algorithms and throughout user code.  These USER_IQ values will differ based on the maximum voltage that could be present on the motor windings (which can be greater than the value measurable by the ADC!!! see section 5.1.2) and the maximum current that may be present in the motor  (5.1.3)

    I've added a new section into the HW QSQ about how to change the hardware and software scalings for the DRV83x designs. This will be in the next MotorWare release on 8/22, but I've attached the relevant document, which is an update to the document normally found:

    C:\ti\motorware\motorware_1_01_00_08\docs\boards\drive\drv8301kit_revD\docs\

     

     

    qsg_hw_drv8301_revd.pdf
  • 0 in reply to ChrisClearman
    Prodigy 120 points

    Perfectly answered Chris, Thanks.

    Thanks for the updated document too.