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DRV10987EVM: DRV10987 – Motor unstable when switching to closed-loop

Krzysztof Kolodziejek
Prodigy 10 points

Part Number: DRV10987EVM
Other Parts Discussed in Thread: DRV10987,

Hello,

I am using DRV10987 with a sensorless BLDC motor and I have a problem during the transition from open-loop to closed-loop.

I have a small BLDC inrunner with 8 poles for fuel pump. The motor works very well with A4949, fully stable, but to increase pump performance, I need to run the motor at a higher supply voltage, so I started testing DRV10987EVM with GUI.

The problem is after the open-loop startup is smooth and stable, waveform becomes irregular anth the closed-loop does not stabilize. Motor hardware verified OK (stable with A4949), motor parameters entered as carefully as possible, Which parameters should I adjust first to stabilize the open-loop → closed-loop transition? Unfortunately, random tuning did not resolve the issue. 

Any suggestions would be very helpful.

Thank you.

Best regards,

Krzysztofclosed_loop_issue.jpg

  • 0
    TI__Expert 6100 points

    Hi Krzysztof,

    Could you please specify the startup mode utilized in your tuning configuration? I would recommend attempting to initiate motor operation using a reduced open-loop acceleration rate. Additionally, please ensure that the open-loop current rate is maintained at a low level. I hope you have followed the instructions provided in the tuning guide for the proper configuration of the device's register settings.

    Thanks,

    Dhinesh

  • 0 in reply to Dhinesh
    Prodigy 10 points

    Hi Dhinesh,

    Thank you so much for your response. Please check my current settings.

     

    best regards,

    Krzysztof

  • 0 in reply to Krzysztof Kolodziejek
    TI__Expert 6100 points

    Hi Krzysztof,

    Please also provide the motor specifications, including rated voltage, current, speed, and inertia. Motor resistance and back-EMF constants are critical parameters for ensuring proper open-loop to closed-loop handoff operation. Hope you have measured these parameters in accordance with the instructions provided in the tuning guide. Additionally, have you attempted testing with reduced first-order acceleration constant (A1) and second-order acceleration constant (A2) values?

    Thanks,

    Dhinesh