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TMS320F28069: speed loop tuning - Oscilation

Gemini1000
Intellectual 500 points
Part Number: TMS320F28069


Hello,

We are using TMS320F28069 to control a sensorless bldc motor; The motor is working great in torque mode however we are having some issues in speed mode where the motor keeps oscillating when we change the load. We have spent so much time tuning the speed loop but didn't help much.  The application's for drones! The motor needs to ramp to 1200 rpm and keeps the speed at 1000 rpm as we change the load. The acceptable rpm variations is within 50 rpm. The motor is rated at 1200 rpm, 42V nominal. Appreciate your URGENT support.

Thanks

  • 0
    TI__Guru** 116510 points

    You have to tune the gains of the speed and torque current PI controllers according to the system, there are no other ways to solve this issue directly. You might try to use different gains of the speed PI controller at high speed and low speed.

  • 0 in reply to Yanming Luo
    Intellectual 500 points

    We have spent so much time tuning the sped PI controller but it still oscillates when we change the load. Any other suggestions? Should we limit the PI output when adding load? What about adding a KD term?  would that help?

  • 0 in reply to Gemini1000
    TI__Guru** 116510 points

    If possible, you might monitor the feedback speed, reference torque current, and actual torque current to know the oscillation is from the speed controller or torque current controller. And you might have to tune both controllers according to the running states.

    It seems like the Kd is used to improve the response. Generally, the PI controller is enough for the current controller. You might try to implement the PID for speed.