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TMS320F28069M: InstaSPIN-MOTION Lab 12a: Cannot get the motor to spin past 5krpm

Asif Ahmed
Expert 1570 points
Part Number: TMS320F28069M
Other Parts Discussed in Thread: LAUNCHXL-F28069M

Hello -

I am currently evaluating InstaSPIN-MOTION for a custom actuator we are building. I am currently using LAUNCHXL-F28069M + BOOSTXL-DRV8305 Hardware and a BLDC motor rated at 360kv (24V).

I have a 4096 cpr magnetic encoder attached to the motor, and attached to the LaunchPad (QEP_A port).

When I run Inertia ID using Lab 5c (sensorless), I am able to get inertia and friction measurements up to the rated 8krpm (I should probably state that there is currently no load on the motor).

However, when running Lab 12a (sensored), I get measurements fine up to about 5.5krpm. Anything higher than that gives Error 2003. However, no matter what value I put into VelIdTorqueRampTime_sec, I still get error 2003. I have tried reconfiguring the encoder for 2048 cpr and 1024 cpr as well with no luck (thinking that maybe that speed was too much for the encoder/QEP port).

Please advise what to look for here.

Lastly, when I use lab 12b to test the velocity controller (using inertia and friction from a valid test ~5krpm) the motor makes unpleasant noise and goes crazy if i try to exceed a certain speed (4krp or higher). I assume this is related to the same issue above?

Any insight is much appreciated!

Best,

asifjahmed

  • 0
    Expert 1570 points
    A quick update on this - I have tried varying the encoder settings (adding hystersis, varying the cpr of the encoder between 1024, 2048, 4096) and I still cannot get past 4.2krpm (exactly). If I go up to 4.25krpm, the motor jumps to maximum speed, sounds bad, and the gMotorVars.SpeedQEP_krpm variable immediately jumps to either a very low number or a negative number. Prior to 4.25krpm everything works beautifully.

    Please help. Adam @ Linestream, I'm specifically hoping you can chime in :-)
    Best,
    asifjahmed
  • 0
    Guru 12800 points

    InstaSPIN-MOTION requires at least three electrical angle samples in order to correctly calculate a feedback speed.  My suspicion is that this limit is being exceeded.  

    Try executing the speed loop at a faster rate to see if that helps.  Note that this will also reduce the resolution of the feedback sensor since we are implementing a pulse counting technique.

  • 0 in reply to Adam D. Reynolds
    Expert 1570 points

    Thanks, Adam.

    I actually resolved this last night by doing exactly what you recommended. Raising the ISR loop speed to 30khz allows me to reach 7krpm.

    I have another issue though - I cannot set the max motor speed in user.h to the motors actual max speed. When I do the program loads and starts up fine, but the motor will not spin. The motion plan never gets executed. Any ideas here?

  • 0 in reply to Asif Ahmed
    Guru 12800 points

    I suspect that you are getting an error somewhere.  Most likely from the PLAN configuration.  Look at the variables under gMotorVars.SpinTAC to see the error codes for PLAN.  There is additional information in the User's Guide.