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My motor not running with weight

Mohammed Alhammadi
Prodigy 130 points

Other Parts Discussed in Thread: DRV8301

Im trying to use my BLDC 48v to run small car that i have build it.

I have done with all labs until 3 and i did inertia id lab also and everything was perfect.

But, when i fixed the motor on my car it wont run it, but when i lift the car and free the tyre, the tyre is rotating as normal an i can control it easily, but when i leave the car on the ground it wont run,!!!!

Is there any other parameters that i have to add it to user.h to make the car run?

Is the problem with the weight ?

When i connect the motor with the controller comes with the motor it runs my car perfectly but i want to use my drv8301 f28069m .

Thanks a lot ,,,

  • 0
    TI__Guru** 119680 points

    Hard to say.

    - are the motor parameters correct?

    - is USER_MOTOR_MAX_CURRENT set high enough?

    - is force angle flag enabled?

    - have you checked that Rs is correct / recalibrated and offsets are correct?

    - are you requesting a large enough torque or speed command?

  • 0 in reply to ChrisClearman
    Prodigy 130 points
    Yes i think the parameters ok,
    My motor 48 vdc bldc and 350w
    USER_motor_max_current is set to 5 by default,
    The force angle is enabled
    Yes the Rs checked and recalibrated
    I dont know how to request and change the torque in the user.h parameter ?

    The motor in the air is running perfectly,
    But on the ground with the car load on it it wont move ?!?
  • 0 in reply to Mohammed Alhammadi
    TI__Guru** 119680 points

    5A of peak current is not enough to produce the required torque.  Try setting to (15)

  • 0 in reply to ChrisClearman
    Prodigy 130 points
    Thanks chris for your fast reply,

    The motor is starting to run with the load but there was a problem which is the response, the motor is gradually start to increases there is a delay before it start to response?!
    And can i ask what is the max current i can use ? Can i put it more than 15?
  • 0 in reply to Mohammed Alhammadi
    TI__Guru** 119680 points
    "The motor is starting to run with the load but there was a problem which is the response, the motor is gradually start to increases there is a delay before it start to response?! "

    OffsetCalc causes a "delay" as it recalculates the ADC offsets. You can disable if the proper offsets are stored in your user.h and compiled into the program.
    RsRecal causes a "delay" as it recalculates the Rs. You can disable if the Rs is valid and stored in your user.h and compiled into the program.

    Any other "delay" will come from your trajectory generator and how you are setting the speed command (acceleration rate).

    "And can i ask what is the max current i can use ? Can i put it more than 15?"
    Peak current needs to be high enough for the peak torque you need to produce. Does your motor have a peak torque spec? Or a torque constant spec? It is higher than the average or constant torque.

    your 350W / 48V motor "signifies" an average current of 7.3A. It likely can take peak currents at least double, that's why I suggested 15A. But the only way to know for sure is if the motor has been characterized and has a specific datasheet.

    With the DRV8301 EVM from the HW side you can increase this to (40) and see if your torque is improved.
  • 0 in reply to ChrisClearman
    Prodigy 130 points

    Thats good thanks chris great information.

    Can you please tell me how to set the offsetcalc and rscalc and where?

    And can i have more information about EMV and how i change it and where?

    Thanks a lot man for your help.

  • 0 in reply to Mohammed Alhammadi
    TI__Guru** 119680 points

    "Can you please tell me how to set the offsetcalc and rscalc and where?"

    this is clearly discussed in proj_lab03b

  • 0 in reply to Mohammed Alhammadi
    TI__Guru** 119680 points
    "And can i have more information about EMV and how i change it and where?"
    I don't understand this question. Are you asking about (40)? Like previous, you can update the USER_MOTOR_MAX_CURRENT