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Force angle mode for startup - getting stuck in a slow shaky spin

subrat nayak72
Expert 1285 points


When my motor starts from zero speed, it has quite some load. If I command is high enough Iq_ref, it picks and keeps moving. Sometimes when I give it small values of iq_ref increments, it gets stuck in a slow shaky mode and any increase in iq_ref doesn't make it speed up, it's just stuck in the super slow shaky mode probably less than 5 rpm. Any ideas what's causing that? I wonder if it's getting stuck in force angle mode.

Are they any settings for force angle mode that I can vary to see if I can fix the problem?

I noticed _IQ(0.01) is hard code in   if(_IQabs(gMotorVars.Speed_krpm) < _IQ(0.01))  in updateIqRef() function . Is that some thing that can be varied ? 

Also, my understanding was that in Lab5a, the Iq_ref is set by hand and the iq_ref values coming from speed controller are ignored. So, what does 

CTRL_setSpd_ref_krpm(handle,_IQ(-0.01)); or CTRL_setSpd_ref_krpm(handle,_IQ(0.01));

given that the speed controller is not active or is it active in force angle mode?

thanks

subrat

  • 0
    TI__Guru** 119680 points
    in torque mode you still need to set a speed reference to the EST so it's direction capability works. That's the reason for the code you mentioned.

    yes, it seems as if you don't use enough Iq current the motor never reaches a speed at which FAST can take over.

    this frequency at which FAST should take over is set by
    #define USER_ZEROSPEEDLIMIT (0.5 / USER_IQ_FULL_SCALE_FREQ_Hz)
    where 0.5 Hz is the frequency

    the frequency of the forcedangle is given by
    #define USER_FORCE_ANGLE_FREQ_Hz (2.0 * USER_ZEROSPEEDLIMIT * USER_IQ_FULL_SCALE_FREQ_Hz)
    and it is critical to keep USER_FORCE_ANGLE_FREQ_Hz >= 2.0 * "0.5 Hz"

    you will have to try different values for "0.5" to see what works best with your motor. Large flux machines somewhere in the 0.5 - 2.0 are usually best, lower flux machines may require slightly higher.

    You may also wan to have a minimum IqRef_A that you allow for start-up, to guarantee that it kicks off correctly.