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TMS320F28069M: Vibration Compensation Issue in Lab11b for Starter Motor

Ram babu
Intellectual 260 points
Part Number: TMS320F28069M
Other Parts Discussed in Thread: MOTORWARE

Hello TI Support Team,

I am trying to write the firmware for a BLDC motor being used as a starter to crank an IC engine using MotorWare Lab11b – Vibration Compensation Example. Using this lab, I am able to achieve a maximum speed of 200 RPM but with unacceptable amount of oscillations when the crank/rotor angle approached the Top Dead Center (TDC) of the IC engine.

As the piston approaches the TDC, the rotor of the BLDC motor starts oscillating back and forth. The rotor oscillates a few times before successfully crossing the TDC, which affects smooth engine cranking of the engine.
I tried with gAlpha values between 0.1 and 0.99 but there was no significant improvement in the performance. 

Could you please guide me on:

  1. How to correctly configure the vibration compensation parameters for starter motor operation given the highly non-linear load profile with respect to the rotor angle. 

  2. Recommended adjustments or techniques to reduce rotor oscillation and vibration during engine cranking. For example, is there a way to poll the rotor angle from the estimator and use feed-forward gain scheduling for Iq_ref?

I am attaching a slow-motion video of the cranking with this email for your reference.

Thank you for your support.

  • 0
    Intellectual 260 points

  • 0 in reply to Ram babu
    TI__Guru** 116290 points

    Seems like you have to keep tuning the Phase Advance and Learning Rate parameters according to the system/motor you are working on. It's challenging to have a recommended value without any testing data. It could be the only way to try run the system/motor to find the correct parameters by yourself. 

  • 0 in reply to Yanming Luo
    Intellectual 260 points

    Hi Yanming,

    Thank you for your response.

    We understand that Lab 11b vibration compensation requires system-specific tuning. However, in our starter-motor / cranking application, the rotor oscillation near TDC is significant, and the vibration compensation block does not appear to improve stability.

    So far, we have tried sweeping the following parameters:

    • gAlpha from 0.1 to 0.99

    • Different learning rate values

    We have not yet varied the phase-advance parameter, as we would like guidance on suitable starting values and safe tuning ranges for this type of application.

    In all tested cases, the motor continues to oscillate around TDC and does not smoothly pass through it.

    To help with further analysis, please let us know what additional data would be most useful from our side. We can provided.

    Additionally, could you please advise:

    1. Whether Lab 11b vibration compensation is intended to handle highly nonlinear loads such as engine TDC, or mainly periodic torque ripple ?

    2. Recommended starting values and tuning ranges for phase advance in starter-motor applications?

    3. If TI has any reference design or application note related to cranking or TDC crossing using InstaSPIN?

    We are happy to share logs, plots.

    Best regards,
    Rambabu

  • 0 in reply to Ram babu
    TI__Guru** 116290 points
    Ram babu said:
    Whether Lab 11b vibration compensation is intended to handle highly nonlinear loads such as engine TDC, or mainly periodic torque ripple ?

    It's only suitable for the compressors load with periodic torque ripple. I am not sure that it's suitable for the engine TDC.

    As mentioned above, you have to tune these parameters according to the system. It's difficult to recommend any values.

    Sorry. Currently, we didn't test this on engine TDC, and don't have any reference design.