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DRV8462: Why do I always get the CNT_UFLW flag if ATQ_LL is bigger than zero

Albert Haberlander
Prodigy 60 points
Part Number: DRV8462

The other parameters are:

ATQ_LRN_CONST1 = 75

ATQ_LRN_CONST2 = 52

ATQ_TRQ_MAX      = 73

ATQ_TRQ_MIN      = 66

ATQ_UL                  = 50

ATQ_LL                   = 10

With these parameters the motor always stalls, If I try to load KP, KD and ATQ_D_THR to any value.

Where could be the fault?

Thanks Albert

  • 0
    TI__Mastermind 21480 points

    Hey Albert,

    The CNT_UFLW flag becomes 1b if ATQ_CNT is less than ATQ_LL. So I'm guessing your ATQ_CNT is 0

    See page 47 of the device datasheet for the algorithm and flowchart for selecting ATQ_TRQ_MIN, ATQ_TRQ_MAX, ATQ_UL, ATQ_LL

    What motor are you using? I want to see if it is one of the motor types that this app note mentions stall detection has issues with:  Sensorless Stall Detection With the DRV8889-Q1

    You can also try the auto learn stall algorithm in the device:

    Auto learning is the left 2/3:

    Best,

    Jacob 

  • 0 in reply to Jacob Thompson
    Prodigy 60 points

    Hi,

    I use the minebea motor 23KM-K046-K21V.

    Now I read out the data from ATQ_CNT and I always get 0 for a long periode.

    Why is this so?

    The datasheet says, that this should proportinal to the meachincal load torque.

    But the motor runs with high load and therefore ATQ_CNT should not be 0.

    Best Albert

  • 0 in reply to Albert Haberlander
    TI__Mastermind 21480 points

    Hey Albert,

    I think it still depends on the tuning of your AutoTorque parameters.  TRQ_COUNT reads the current output more automatically, but ATQ_CNT needs some help being tuned in to a particular motor.  

    What does your TRQ_COUNT reading say?  

    And do you have an EVM you can test this with our web GUI? That might make your debugging easier

    Best,

    Jacob

  • 0 in reply to Jacob Thompson
    Prodigy 60 points

    Hi,

    I'm sorry but the PD controller driver doesn't work.

    The motor has to drive a membrane pump. So the torque is nearly sinusoidal.

    When I read out the ATQ_CNT I get values between 0 and 115. So I set the UL to 120 and the LL to 0.

    The pump runs with a constant speed. When I check the motor current on a scope, than I see no variation on it.

    I tried values from 1 to 200 for KP and 0 to 100 for KD and 2 to 5 for ATQ_D_THR but the current is always the same.

    What could be wrong.

    Best Albert

  • 0 in reply to Albert Haberlander
    TI__Mastermind 28295 points

    Hi,

    Thank you for your question. May 27th Monday is national holiday in US. Will feedback to expert back office.

  • 0 in reply to Albert Haberlander
    TI__Mastermind 21480 points

    Hey Albert,

    Give me another day to try and get some help from a coworker on this that has more experience with this.  

    Best,

    Jacob

  • 0 in reply to Jacob Thompson
    TI__Mastermind 18295 points

    Hi Albert,

    Thanks for sharing the stepper motor and the auto torque settings information. I was unable to find information on the Minebea motor 23KM-K046-K21V. the closest I could find was the https://nmbtc.com/parts/23km-k044-00v/. Is this reasonably close to the specifications of the motor you were using? If not please share its datasheet.

    What was the VM voltage used and the VREF voltage used - internal or external how many volts if external via VREF pin? What were the auto torque Max and Min current limit settings? and the lowest current required for the motor to run without stalling in your end application. If you could please also share with us the current waveform of either the A or B phase. Thank you.

    Regards, Murugavel