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28335 HVPM Sensorless example code. Sensorless speed control not working right.

Brad Mularcik
Intellectual 580 points

I am running the example code from Control Suite for the HV Kit for Sensorless PMSM control.  I am at build level 6.  I actually modified build level 5 so that I can run either sensorless or with the encoder by changing lsw from a 2 to a 3.  I basically combined build level 5 and 6 using lsw as the switch.  When I run with encoder feedback, the motor runs in velocity loop very nicely.  I can load the motor and the speed stays constant, but current goes up.  I can see the current demand by looking at the value of pid1_iq.Ref.  This changes from 0.09 with no load to .99 with a heavy load.  This is what is expected.  However, when I run with sensorless, I cannot load the motor very much before it stalls,  As I load the motor, pid1_iq.Ref goes up, but when it gets to about 0.2 or 0.3, the motor stalls.  I am viewing qep1.elecTheta (the encoder position) and smo1.Theta (estimated position from sliding mode observer) on a scope.  With no load, they are in synch.  However, when I load the motor, they move out of synch.  It appears that the smo1.Theta advances relative to the encoder when spinning CCW and retards when spinning CW.   I have played with the sliding mode observer gains, but I really do not understand the sliding mode observer, so I really do not know what I am doing with that.  It seems that adjustments of either gain up or down from where I have them now make it worse, not better.

Please advise what I might do to solve this problem.

Thank You,

Brad

  • 0
    Intellectual 580 points

    It has been nearly 2 weeks since I posted this question / issue.  I have not heard any response.

    Please help.

    Thank you,

    Brad

  • 0
    TI__Intellectual 930 points

    Brad,

     

    Are you using the PM motor comes with HVDMC kit?

    The PM project is tested in the 0.2-0.8 pu speed and 0-0.5 pu rated load range, so you should be able to load 0.3 pu. Beyond these ranges you may need to tune the PID and smo.kslide coefficient. Make sure that you provide enough dc bus voltage and not saturate the PID outputs. The filter delay in SMO might cause ~10% phase delay depending on the operating speed which might need to be compensated in you case. In order to spin the motor at negative speed range you have to negate the smo inputs. Make sure that you are not overloading the motor, 1.0 pu=20A peak current and the rated current for this motor is 2.7A rms.

     

    Regards

    Bilal