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Sensorless FOC PMSM control

Jesus Perez
Intellectual 260 points
Other Parts Discussed in Thread: CONTROLSUITE

Howdy,

A colleague and I are trying to implement sensorless FOC using TI's High Voltage Motor Control+PFC kit. We are driving  a permanent-magnet synchronous motor with the kit. Originally most of the motor parameters were unknown and we were unable to close the speed loop per the incremental build system outlined in the documentation. We experienced lots of vibration and high current draw during open-loop operation and when we closed the speed loop the motor would pull out and overcurrent the power supply. 

We've recently determined the parameters of the machine we are working with. While driving the motor in open-loop we still have lots of vibration and audible noise. We can now close the speed loop but the motor stops very quickly then restarts. The current is lower than in open-loop mode but the vibration is still there. We also noticed that the speed is higher in closed-loop than in open loop by about 200 RPM. Furthermore, we are not always able to close the speed loop successfully.

If anyone could give any insight on how to get rid of the vibration and how to properly tune the PID gains it will be much appreciated. Thank you very much beforehand! :)

  • 0
    TI__Guru** 118750 points

    PI tuning is one of the "black magic" areas.  Some people try simulation tools, some people use a procedural method, and some seem to have a natural intuition.

    I'd first suggest making sure you are using the pid_grando PI controller from motor_lib v3.1

    I'd then suggest - if you can - tuning first with a sensor.  Matching the QEP angle to the SMO angle is critical to isolate only the PI controller.

    Make sure you start with something nominal like 30% rated speed, no load.

    Solving and automating this process would be quite beneficial, wouldn't it?

     

  • 0 in reply to ChrisClearman
    Intellectual 260 points

    Hi Chris,

    Thank you for the suggestions. I am using whatever PI controller was included into the PMSM_Sensorless project from controlSUITE. Should I replace it with the pid_grando module?

  • 0 in reply to Jesus Perez
    TI__Guru** 118750 points

    I don't think it will magically solve your problems, but at some point I would move to PID Grando

    Tuning the PI controller is "black magic". To do it manually the way it's typically done is to set Ki = 0 and start moving Kp up until you reach oscillation.  Then your Kp value should be set to 1/4 - 1/2 of that value, then you start tuning Ki upwards.

     

  • 0 in reply to ChrisClearman
    Genius 5170 points

    I found this tuning process behaving better with some load... Under no-load condition it becomes challenging to overcome back EMF to obtain any well behaved current signature. But as mentioned ...tuning these loops is still in kind of "trial and error" process and takes some time to get it correct.

  • 0 in reply to Arefeen
    Intellectual 360 points

    Hello, I am new in this forum.

    My problem is that I have to finish a master thesis, that includes the control of an asynchronous motor. The simulation in powersim works just fine, even using discrete controllers. Now I am having to program this on a 320f28335. Unfortunately, my search for application notes were not as successful as I would have liked.

    Is there a manual that indicates step by step for beginners, how I configure two ADC-inputs for 40kHz sampling, read the results, get 20kHz PWM on 6 outputs (three active low, 3 inverted, activ high), configure the deadband etc. for absolute beginners like me? I have found DMC-libraries from TI, but I do not understand them, also, as I am not that familiar with the floating point format.

    Looking forward to your answers.

     

    regards

  • 0 in reply to E_
    Intellectual 260 points

    Erich,

    If you download ControlSUITE from TI you will get a lot of documentation for this. It is not by any means everything you need for your thesis but it's a good starting point. You can find hardware design app notes under the Motor Control modules as well as firmware code under the Projects pane. Hope this helps.

  • 0 in reply to Jesus Perez
    Intellectual 360 points

    Gracias Jesús, veré lo que puedo hacer, porque muchos enlaces parecen estar muertos.

    saludos

  • 0
    Intellectual 270 points

    HEHE, its a old problem of all the sensorless FOC kit. Please refer to http://e2e.ti.com/support/microcontrollers/tms320c2000_32-bit_real-time_mcus/f/171/p/97761/406704.aspx#406704