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LAUNCHXL-F28069M: Selecting the right Encoder for PMSM traction motor

Jesal Patel
Intellectual 840 points

Part Number: LAUNCHXL-F28069M
Other Parts Discussed in Thread: MOTORWARE

Hello there,

 I've been working with controlling of PMSM traction motor with FOC; herein i'm using the LAUNCHXL 28069m . I require some guidance regarding the encoder to select for traction control .

The encoder which can be easily communicate with the LAUNCHXL and also i require some resource on data handling of the encoder ..

  • 0
    Expert 2550 points

    Dear Jesal Patel,

    In my experience with LAUNCHXL-F28069M and InstaSPIN-FOC, you can use an Incremental Encoder for your application. Based on MotorWare library, you can easily interface with Incremental Encoders (or QEP encoders) to get position and velocity info which is necessary for FOC algorithm.

    A problem is you should choose carefully the revolution of Encoder to be suitable for your requirements.

    Regards,

  • 0 in reply to Tran Binh Duong
    Intellectual 840 points
    Dear Tran Binh Duong,

    I refered your point regarding the Incremental Encoder, but i have a doubt regarding the event which may arise at the starting of the system i.e. when the index pulse may not show up, so at that point how to get the angle information frrom the encoder?
    one more point is how to map the encoder data to generate PWM signal.

    hoping for a reply soon
  • 0 in reply to Jesal Patel
    Expert 2550 points

    Dear Jesal Patel,

    I have tried with enc.h/enc.c module in the set of MotorWare Library, I did not meet the issue which you are worried about.

    InstaSPIN-FOC and InstaSPIN-MOTION does a task called "forcing alignment" in which the Encoder angle is aligned with the rotor angle in order to ensure that the position info always gets right value at right time.

    You can refer Lab12a, 12b to verify this feature.

    Hope to help!

  • 0 in reply to Tran Binh Duong
    Intellectual 840 points

    Hello Tran Binh Duong,

     greetings of the day !

    Thank you for the support. I'll work on what you reffered to.

  • 0 in reply to Jesal Patel
    TI__Guru 57255 points

    Hi Jesal,

    Using an incremental optical encoder will likely work well (and work with the launchPAD).

    However, I wanted to add two notes:

    1. Incremental encoders can get dirty in traction systems and in many systems, a resolver may be a more optimal choice.  The C2000 has some software example projects/hardware examples that give an example of how someone might use a resolver.  This would require some additional circuitry than what is on the launchPAD though.  This might end up being a potential future improvement.
    2. You can use the FAST sensorless observer to cross-check with what comes out of your incremental encoder (or resolver) for increased robustness in your system.


    Thank you,
    Brett