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coupled motor

Morikeh Daramy
Intellectual 480 points
Other Parts Discussed in Thread: DRV8301

HI

I am using the f28027f Launchpad with DRV8301 booster pack motor driver and maxxon BLDC motor. This set-up is coupled to the f28069f controlCARD with DRV8312EVM inverter board and NEMA 17 motor.

I am attempting to run the maxxon motor as a Motor-Generator.

I have my control algorithm, which appears to rune fine. however,

when the maxxon motor side is running in motor mode it is unable to drive the system beyond the speed determined by that on the NEMA 17 side!

This is undesirable, for example;

If the NEMA 17 side is running at 200rpm but I want the Maxxon side to drive the system at 700rpm, the speed reference on the maxxon side changes, but the speed remains capped at 200rpm!

From the sounds of things, it seems as if the maxxon rotor is locked at the NEMA 17 rotor speed and demanding a greater speed simply increases the rate of switching of the phase currents.

hence rotor speed is locked.

-Is this analysis correct?

-why is this happening?

Main question:

How can I fix this?

I am thinking that I could fix this by using field weakening?

I am managing the problem, at this time, by switching the run_identify switch on the NEMA 17 side, on and off at the appropriate time.

Thank you for your support

  • 0
    TI__Mastermind 27240 points
    I guess the NEMA 17 motor is on speed loop, and you are trying to pull in another motor to control the same shaft speed to 700 rpm. Looks like the NEMA motor is able to torque the motor to stay at 200rpm. If you review the control at the abstract level, you may be able to figure out a solution.
  • 0 in reply to Ramesh Ramamoorthy
    Intellectual 480 points
    If the Nema 17 is in speed loop, then the speed reference determine the Iq value that is sent to the Iq controller.

    If I am correct, setting the IqRef value to a lower value would not produce the desired outcome.

    I have tried adjusting the controller gains (all three controllers) in order to reduce the stiffness of the rotor of the NEMA 17.

    I am not quite sure of I am along the right track.

    Thanks
  • 0 in reply to Morikeh Daramy
    TI__Mastermind 27240 points

    Hi,

    I don't know what else to say, looks like two controllers are trying to control the shaft speed of two coupled motors to different speeds. The lower speed motor is trying to regulate the speed by providing enough counter torque to overcome the other motors' torque. Probably the higher speed commanded  motor is at its torque limit and cannot produce anymore torque to overcome the low speed motor's torque.

    You may have to investigate a bit more.

    rgds,

    rameshj