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DRV10974: Fail to go out of open-loop

Part Number: DRV10974

Hi,

I am struggling to run Maxon's 283828 motor:

https://www.maxongroup.com/medias/sys_master/root/8882350882846/EN-21-245.pdf

Compared to those recomendation:

Is BEMF parameter possible to calculate having informations from motor's datasheet? Because it is the only one I am not sure is respected.

Resistors used in project (actually 0,5W potentiometers):

CS -> 36k,

RMP -> 7,32k (datasheet default),

ADV -> 59k (datasheet default).

I am using 0-1,8V analog value to speed control.

And what results I got? Motor spins for some time accelerating, but stops suddenly, after 5s process repeats. Closed loop mode doesn't activate.

I have used different resistors, but it didnt help.

This is a whole process:

And this enlarged

Yellow is U voltage, blue is FG pin output. Looks like driver is tries to run that motor, but encounters some failures.

Can you tell me please if it's true, that this motor can be controlled by DRV10974? If yes, is the problem in bad callibrating?

Thank you for your help. If you need more information or tests I will deliver them as soon I can.

  • Hi Patryk,

    Thanks for posting your question in MD forum. I checked the motor datasheet and DRV10974 should be able to spin this motor. Did you check the DRV10974 tuning guide? Please refer to the quick tuning and comprehensive tuning sections for steps to tune the motor.

    Can you share the phase current waveform? It looks like the device is triggering Abnormal BEMF constant fault which prevents the motor from entering into closed loop. This fault gets triggered when the estimated BEMF constant does not match the self-measured BEMF constant. I would recommend you to play around with ADV resistor. This resistor sets the lead time. Adjusting the lead time will ensure the estimated BEMF constant matches self measured BEMF constant. Since the motor resistance is higher, lead time for this motor might be around 10 µs to 100 µs. Check section 3.3 in the tuning guide for more details.

    Regards,

    Vishnu

  • Thank you for your answer.

    Here are some U current waveform based on voltage measurements on a 1 Ohm resistor:

    Waveform start (higher current limit)

    Wafeform middle (higher curtent limit)

    Waveform start (lower current limit)

    Waveform end (lower current limit)

    Looks like noised sinusoid with frequency increasing every cycle.

    So considering what you have said and documentation (image below), we can see on waveforms, that every cycle's integrating value is getting lower. Am I right? If there must be BEMF constant calculated, sin amplitude should increase with frequency.

    I'll try change ADV resistor and observe current changes.

  • Hi Patryk,

    DRV10974 measures BEMF voltage and calculates BEMF constant during open to closed loop transition. Figure 7-9 shows the BEMF waveform which is different from the phase current waveform. 

    Please adjust the lead time by changing the ADV resistor and let me know if you see any improvement. 

    Regards,

    Vishnu

  • Hello Patryk,

    Do you need any further assistance on this thread?

    Thanks,

    Matt

  • Hi Patryk,

    I will close this for now, since I haven't heard a response back. If you want a follow-up, please feel free to reply to this thread or create a new thread.

    Regards,

    Vishnu