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DRV10983: Motor driver do not draw current or drive motor even if the speed registers show the command

Part Number: DRV10983

Dear Sir,

We use a DRV10983 IC in our motor driver unit for driving a maxon motor. The assembled unit is finally for a drone application. The units work fine in ground but in cases with Drone Rotor Thrust above 10%, multiple units fail to start at random times (Drone and the motor units are fed from the same battery supplies through DC-DC converters). We had implemented a data logging that reads from the DRV10983 registers to see what is the driver status when the failure occurs. The following are the major observations:

1. The external PWM command from a micro-controller is received properly at all times through the I2C communication during the issue.

2. The internal speed command registers (0 - 511) also follow the required speed command during the issue

3. The supply Vcc to DRV10983 IC also is present throughout the duration of the issue

4. No faults - neither status nor lock - is recorded during the issue.

5. For some reason the motor current draw is near zero (~0.01 A)

6. Also, the speed registers which record the actual speed shows sub 500 RPM values, with no actual real world rotation observed

7. Once the Drone Rotor Thrust is brought down below (30% - 10%), the motors resume operation automatically

Kindly shed some light as in how else can the Driver IC not draw current or drive the motor in a non-fault condition

1. The figure titled 'Normal Turn-ON Operation Current' shows the current values recorded from driver current registers when the motors start operation normally

2. The figure titled 'Failure to Start Current' show the current behavior recorded from driver current registers when the motors fail to start under drone rotor thrust 45% till horizontal axis value of 397 and;
     beyond that is when drone thrust is brought down to 30% and motors resume operation

Thank You,

Jain James

  • Jain,

    I believe the motor is getting overloaded when the thrust increases and you are not seeing any faults because I'm assuming all faults are disabled. Can you enable all faults and check what faults are getting triggered when thrust increases? Also, is it possible to monitor the phase current on an oscilloscope when the thrust is higher?

    Regards,

    Vishnu

  • Dear Vishnu,

    Just to clarify the motor unit that we use the DRV108983 to drive is not the one used for the drone rotors. They are external rotor mounted on the ends of the drone arms above where our motor units are mounted.

    I understand your point. Yes, currently the faults are disabled but even so, correct me if I am wrong, the faults still used to be detected but not acted upon when they are disabled. Our earlier data-logs and your data-sheet  (Attaching screen capture) suggests the same.

    Monitoring the phase currents using non-intrusive probe while the drone rotors are live is very difficult. Although with no guarantees, we will see the possibility of the same.

    We rely on the internal current registers because, in the past except the first and the very last values read from these registers current drawn used to be fairly accurate.

    Is there any specific reason why TI do not recommend reading from these internal current registers?

    Also, if possible could we hold a meeting to resolve the queries, that would be helpful or a number to contact

    Thank You,

    Jain James

  • Jain,

    I've sent you a request.

    Could you accept my friendship request? We can chat over there.

    Regards,

    Vishnu

  • Hi Vishnu,

    I had accepted it on Friday itself. Could you please expedite further steps or info you need?

    Thank You,

    Jain James

  • Hi Jain, 

    Vishnu is OOO today but we will aim to give a response to you when he returns, before end of this week. 

    Best Regards, 
    Andrew 

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