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Lab 9 discrepancy

John Sharp59
Prodigy 20 points

Other Parts Discussed in Thread: BOOSTXL-DRV8301

I bought the LaunchXL- F28027F and BoostXL-DRV8301 to use in a small rotating test fixture.   Using CCS 6.1.2 I've been able to work through the labs up to 5b, and even with a $12 hobby motor (USER_MOTOR_Rs = 0.072, USER_MOTOR_Ls_d  = 6.0e-06, USER_MOTOR_RATED_FLUX = 0.0038) I'm getting better results than with the brushed motor & simple PWM controller it replaced.  When I try Lab 9, the motor still runs fine but the variable gMotorVars.Vs never changes from 0.0, nor do Vd, Vq, Id_A, Iq_A, or Is_A.  I've set gMotorVars.Flag_enableFieldWeakening to 1, is there something else that I've missed for this lab?

  • 0
    TI__Guru** 119680 points
    "When I try Lab 9, the motor still runs fine but the variable gMotorVars.Vs never changes from 0.0, nor do Vd, Vq, Id_A, Iq_A, or Is_A. "

    I didn't go run myself yet, but these variables are getting updated in the source code. Are you sure you have Continuous Refresh enabled in the Expressions window?

    "I've set gMotorVars.Flag_enableFieldWeakening to 1"
    the type of motor you are using isn't meant to use field weakening with. Field weakening will barely work with a motor with such low inductance / large short circuit current / low flux.

    for higher speeds you should try using lab10 over-modulation
  • 0 in reply to ChrisClearman
    Prodigy 20 points

    OK, I am the culprit here.  I have been importing the labs one by one as I went through them, and I carelessly pulled Lab 9 out of the drv8301kit board directory rather than the boostxldrv8301 one.  DOH!

    As it turns out, I really didn't need to go beyond Lab 5b.  I was having some trouble with accelerating the system past 7-8K rpm but it was resolved by spending a little more time playing with the PI constants in the speed controller.

    Thanks for your help!