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F28027F & BoostXL DRV 8301. Project lab 5b - where to find sample frequency?

Michiel Vanrompay
Intellectual 490 points

Hi all,

I am doing some work with the lab examples and have run into a little problem whilst following some of the calculations in the pdf.
The KpSeries value has to be calculated using the controller Bandwidth as shown below.

 (P 108 in pdf)

In order to get the controller Bandwidth value I have to make the following calculations.

 (P 102 in pdf)

In this formula the sample frequency (Fs) needs to be filled in, however there is no explanation on how to get this value.

The example right above this formula shows a sample frequency of 10KHz. But is this specific to the motor they are using in this example or is this a general value that can be used with any motor?

(P 102 in pdf)

Thanks in advance,

Michiel Vanrompay

  • 0
    TI__Guru** 118000 points
    Micheil,
    The sample frequency is set in user.h
    You can follow the DECIMATION section of SPRUHJ1

    PWM freq = USER_PWM_FREQ_kHz
    ADC Sampling freq = USER_PWM_FREQ_kHz / USER_NUM_PWM_TICKS_PER_ISR_TICK
    Control System freq = ADC sampling freq / USER_NUM_ISR_TICKS_PER_CTRL_TICK
    Current Control freq = Control system freq / USER_NUM_CTRL_TICKS_PER_CURRENT_TICK
    Estimator freq = Control system freq / USER_NUM_CTRL_TICKS_PER_EST_TICK
  • 0 in reply to ChrisClearman
    Intellectual 490 points

    Hi Chris,

    First of all thanks for your feedback.

    What do you mean with the DECIMATION section of SPRUHJ1? I have never heard about SPRUHJ1 before I'm afraid.

    Is the Estimator Freq in your formula's supposed to be equal to the sample frequency? Otherwise I do not see why I need to perform these calculations.

  • 0 in reply to Michiel Vanrompay
    TI__Guru** 118000 points

    SPRUHJ1 is the User's Guide.  You should read it when you have questions.

    The estimation and sample frequency are sometimes the same. They are user configurable.