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TMS320F28054M: Inertia identification ->

Mika Bay
Intellectual 600 points
Part Number: TMS320F28054M

I am trying to implement Lab5c, which has an inertia identification demo. The lab works fine, but immediately after identification of inertia, the motor starts rotating back (a second or two later) with a jerk. What is the reason for same? Is there a way to avoid startup jerk?

  • 0
    Guru 12800 points

    Mika,

    In lab 5c the speed reference is held at ~200rpm so that the FAST estimator will not lose the motor angle at the start of the test.  So after the test is complete, the speed reference will return to 200rpm.  My guess is that the ramp generator may not be getting set correctly after the inertia test is complete.

    It is also possible that FAST lost the angle in the brief time that the motor is stopped and the jerk is FAST correcting the control of the motor.

  • 0 in reply to Adam D. Reynolds
    Intellectual 600 points

    Thanks Adams,

    Is it possible to set motor speed to zero before and after test -> where can I handle ramp generator and?

    How does in general force angle works, is there any TI document?

    What does EST_getFm_pu(ctrlObj->estHandle); function do -> Does it give motor frequency?

  • 0 in reply to Mika Bay
    Guru 12800 points

    It should be possible to modify the motor speed before and after the test.  There is a variable called gMotorVars.StopSpeedRef_krpm where you can modify the speed it goes to after the test.

    Mika Bay said:

    How does in general force angle works, is there any TI document?

    What does EST_getFm_pu(ctrlObj->estHandle); function do -> Does it give motor frequency?

    You'll need one of the TIer's to weigh in on these questions.

  • 0 in reply to Adam D. Reynolds
    Intellectual 600 points

    Adam,
    Thanks for help.
    Actually I am only interested to find out why motor has jerk after inertia identification.
    I observed gMotorVars.SpeedRef_krpm = gMotorVars.StopSpeedRef_krpm; lines in

    function ST_runVelId().however this jerk occures even if I set end speed to zero. Secondly 

    the jerk occures after around 2 to 3 seconds aftermotor inertia and friction are
    updated in the CCS expression window.So bassed on your advise, is there way to
    find out if FAST is loosing out the angle? If yes, what can be done to
    control/minimize/eliminate it?

  • 0 in reply to Mika Bay
    Guru 12800 points

    I'm not sure what is causing that jerk in your system.

    Mika Bay said:
    So bassed on your advise, is there way to find out if FAST is loosing out the angle?

    I can't really speak for the FAST software.

    Mika Bay said:
    If yes, what can be done to control/minimize/eliminate it?

    I'm not sure how big of an issue this will be in your end application since the inertia identification is designed to be ran during design time and not in end applications.  But you could set gMotorVars.Flag_Run_Identify to false after the inertia identification is completed.  That will for sure remove the jerk.