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TMS320F28054M: TMS320F28054M

Mika Bay
Intellectual 600 points

Part Number: TMS320F28054M

I have a custom f28054m board for motor control. Things are working fine, however during startup, the motor sometimes wobbles little back and forth a bit (2 to 3 degrees) before starting normally. I observed on CRO and found out that when wobbling occures, the three phase current passing through motor reaches motors rated current. I am therefor suspecting that if motor rotor doesn't latch up with current vector at startup, this condition occurs - Is there a way to overcome/minimize this.

Points:

1. Is related to motor tuning especially speed loop tuning parameters?

2. Is this related to motor acceleration?

(Practically I found no specific relation)

is it possible to fine tune motor starup (force angle?) by adjusting parameters like

#define USER_ZEROSPEEDLIMIT or

#define USER_FORCE_ANGLE_FREQ_Hz

Any other guideline to fine tune motor starup against heavy (30times motor inertia) and rated torque? The motor runs on analog input and minimum speed allowed is 100rpm

  • 0
    TI__Guru** 116670 points
    1. The regulator parameters od speed can improve the startup current, can't avoid the running back which is for the initial position is not correct.
    2. Refer to Chapter 14 of InstaSPIN user's guide, enable offset and Rs recalibration, enable force angle. The two parameters you listed is for force angle, you can change it based on your system requirement.
  • 0 in reply to Yanming Luo
    Intellectual 600 points

    Thanks. I have enabled offset calibration, but is Rs critical for startup or runtime?

    Secondly are there any guidelines for setting the two parameters for force angle mentioned in my earlier mail?

    I think in force angle, the dsp rotates the current vector at " USER_FORCE_ANGLE_FREQ_Hz " frequency till fast takes over the theta calculation, am I right?

    If so, does it make sense to reduce rotational frequency so that rotor does start rotating with stator current vector?

    Also will reducing profile acceleration parameter help?

    Finally one more point: Is USER_VOLTAGE_FILTER_POLE_Hz parameter critical here? Since I am using f28054m dsp, which has internal amplifier for all AD inputs, will this value need to adjusted from the value given in documents ie 1/(2*PI*C*R)

  • 0 in reply to Mika Bay
    TI__Guru** 116670 points
    1. Rs is critical for startup with heavy load, not very sensitive for run time.
    2. Force angle is only for startup to generate the rotor angle without rotor position estimator during very low speed. You can change USER_ZEROSPEEDLIMIT and USER_FORCE_ANGLE_FREQ_Hz to adjust it as the description in InstaSPIN user guide.

    USER_VOLTAGE_FILTER_POLE_Hz is calculated according to voltage sensing circuit, not related to current sensing. Don't need to change it though the internal amplifier is used.