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DRV10987: DRV10987 debugging software problem

Annie Liu
Genius 10295 points

Part Number: DRV10987

Hi Team,

Customer is experiencing an issue need your help.

1. When the motor is in the open loop state, the speed is maintained at about 200 rpm, the phase current is between 1.7 and 2.5, the current is too large, and the speed cannot reach the predetermined speed of 1000 rpm or more.
2. The motor cannot rotate continuously in the closed loop state, and can only rotate intermittently, showing overcurrent protection.
3. Motor R=0.4; V=24; I=1A; the predetermined speed is around 1500 rpm.

May I know what's wrong. Or please provide a copy of your debug data based on the data.

Thanks.

  • 0
    TI__Expert 6065 points

    1) I highly recommend please refer to the tuning guide to see ho to tune the DRV10987 to spin your motor http://www.ti.com/lit/ug/slou477/slou477.pdf . 

    2) If you are looking for settings to start with, please find them attachedannieE2eConservativeSettings.csv

    You need to insert the correct phase to center tap resistance and Kt Bemf constant.

  • 0 in reply to Sanmesh Udhayakumar
    TI__Genius 10295 points

    Hi Team,

    Please kindly help to provide a formula for calculating the Kt value. Customer tried the formula in the document, but it doesn't work.

    Whether the Kt value is the only certain value?
    Whether the resistance value is the resistance between any two phases divided by 2?

    Thanks.

  • 0 in reply to Annie Liu
    TI__Expert 6065 points

    I'm assuming you used the equation below:

    You can also try to measure kt by manually spinning the motor quickly or coast it, and use an oscilloscope to capture the differential voltage

    waveform between any two phases, as detailed in the tuning guide.

    You can guess if the kt is correct by looking at the BEMF constant Kt measurement in the display tab of the gui and seeing if it roughly matches what you ented.

    The resistance entered is the resistance between any two phases divided by 2.

  • 0 in reply to Sanmesh Udhayakumar
    TI__Genius 10295 points

    Hi Sanmesh,

    Thanks for your answer.

    Using a sliding motor to measure, whether it is to measure the back electromotive force of any two phases of the motor at 1000 rpm, and then divide by 1.732 to get the Ep in the formula? Does the cycle time is the period displayed on the oscilloscope?

    The customer would like to confirm the method he said or provide a specific method for measuring EP and cycle. Customers think that the resistance should be no problem. There is a problem with the test. It should be that Kt is not accurate enough or for other reasons.

    Thanks.

  • 0 in reply to Annie Liu
    TI__Expert 6065 points

    I do not know what the following terms are:

    a) What is Ep?

    b) why do you divide by 1.732? 

    c) What do you mean when you say "Does the cycle time is the period displayed on the oscilloscope?"

    If you are looking for a reference on how to measure the kt, you can view this video from time stamp 1:01 https://www.youtube.com/watch?v=ix7YPvBtbvE