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TMS320F28334: Flying start

Part Number: TMS320F28334

Tool/software:

Dear Team,

I hope this message finds you well.

I am currently working with the TMS320F28334 and a 1.2kW sensored BLDC hub motor, which I am running using sine commutation on a single shunt topology. At present, I am utilizing a cascaded control scheme with the RPM PID operating at 1 kHz and the current PID at 10 kHz.

I have a few questions regarding the control behavior under specific conditions:

1. When the user fully accelerates the motor to its maximum RPM and then suddenly releases the throttle, the motor continues to rotate due to external forces and gradually decreases its RPM. If the user reapplies full throttle during this deceleration, what acceleration value should be provided to the motor?
2. Considering that the motor stop time depends on the load it is carrying, how should the above scenario be managed under varying load conditions?
3. How should the PI controller be handled in this situation?

Additional Notes:
- I turn off the PWM when the user releases the throttle.
- I calculate the electrical angle using the motor's built-in hall sensor in all situations.
- From my research, I understand that this situation is generally referred to as a "flying start" in the TI forum. However, I am seeking guidance on how to implement this logic in a sensored BLDC motor.

I would greatly appreciate your guidance on these matters.

Best regards,
Dipak
  • If the user reapplies full throttle during this deceleration, what acceleration value should be provided to the motor?

    It depends on the system and motor requirements, no special value can be recommended for you.

    2. Considering that the motor stop time depends on the load it is carrying, how should the above scenario be managed under varying load conditions?

    Continue to detect the rotor position angle and rotation speed when release/stop the motor, and use the latest angle and speed to restart the motor with flying start as you mentioned in the title.

    3. How should the PI controller be handled in this situation?

    You can keep using the PI controllers as normal operation, just set the feedback with the latest detected speed as mentioned above.

    You can take a look the lab guide below that has an introduction about flying start method.

    Universal Project and Lab User’s Guide: https://www.ti.com/lit/spruj26

  • Hi Yanming Luo,

    Thanks for the reply!!!

    I have Chinese controller and I don't have motor parameter like motor inductance, resistance and other values.

    I have only  pole pair information so based on that how to implement fly start as described  in is09_flying_start.c file?

    Please help me how to implement in sine commutation? 

    Best and regards,

    Dipak

  • Correct. You can refer to the reference to implement the method on your project, it can be for FOC with sinusoidal. You can take a look at the lab user's guide, just need to always detect the rotor angle and speed, and use them when you re-start the motor.

  • Hi Yanming Luo,

    I hope this message finds you well.

    I have developed a code that continuously monitors the motor angle and speed and adjusts the PWM accordingly.

    I have a few questions regarding this:

    1. If the e-bike is descending a slope without electrical commutation at 100 RPM (with a maximum RPM of 600), and I apply acceleration midway, what could happen if the acceleration is either too low or too high? Specifically, could this cause the motor to jerk or get stuck momentarily, and is there a risk of damaging the circuitry?

    2. In the same scenario, how would the situation differ if there is a single person seated on the e-bike compared to having three people seated on it?

    Additionally, how should I determine the appropriate duty cycle to apply to the motor in these situations?

    Your insights and guidance would be greatly appreciated.

    Thank you very much for your help.


    -Dipak

  • what could happen if the acceleration is either too low or too high? Specifically, could this cause the motor to jerk or get stuck momentarily, and is there a risk of damaging the circuitry?

    The flying start doesn't matter the acceleration.

    Additionally, how should I determine the appropriate duty cycle to apply to the motor in these situations?

    The PWM duty is determined by the current and speed controllers automatically