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CCS/LAUNCHXL-F280049C: Uncentered currents with increasing speed

Kai Schiffer
Prodigy 80 points

Part Number: LAUNCHXL-F280049C
Other Parts Discussed in Thread: DRV8301, MOTORWARE

Tool/software: Code Composer Studio

Hello everyone,
Here's the problem. I run a PMSM with a Piccolo Launchpad and the drv8301 Boostetpack. The software is the same as Proj_lab08 and has been modified. The modification refers to the application within the 50us task. Accordingly, the handcoded version of Texas Instruments was replaced by a model-based version. The angle information and velocity are still taken from the FAST Estimator. The control is done by Pi controllers in the parallel structure (Speed/Currents). Now the solution works quite well but there is a problem unknown to me and I don't know yet what could cause it. With increasing speed one of the phase currents travels downwards from the center. The behavior is stable at first. The shape and amplitude of the current do not change either. If the speed is further increased, the centre of the one phase current decreases further and further until the system becomes unstable and the control is switched off.
Does anyone have a clue what to look for to fix the fault? The whole thing is for a student research project.

Thank you very much!

  • 0
    TI__Genius 17175 points

    Are you using lab 08 from Motorware on the F280049C device? If so, these examples aren't compatible with the F280049C device

    One of the three feedback op-amps is a dedicated IC instead of integrated into the DRV8301. Can you check if the phase that is drifting is tied to this external op-amp? It's listed as phase C in the schematic. Also, please check if the 3.3V rail is drifting; if so, this could be the cause of the drift you're seeing

    Sean

  • 0 in reply to Sean Bigley
    Prodigy 80 points

    The problem's over.  The solution was to be found in the control parameterization of the D-current cascade.  The estimator calculates the motor parameters with the code from lab05.  It does not consider reluctance due to different longitudinal and transverse inductances.  In a manual parameter identification, Ld & Lq was determined correctly and the controller parameters determined manually.  With these the problem is solved.

    Thank you very much!