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MCT8329A: Gradual start up of motor

Ron Wilton
Prodigy 60 points
Part Number: MCT8329A

Tool/software:

Hello

Is it possible to get the motor to start up very slowly and gradually build up to the desired speed using a MCT8329A motor controller?

I'm finding that the motor runs at a higher frequency before dropping down to the desired speed. There is also a jolt as the motor starts up.

Thanks

  • 0
    TI__Genius 9210 points

    Hi Ron,

    You could try changing the open loop and closed loop acceleration settings :

    • decrease the Open Loop acceleration rates: [OL_ACC_A1] and [OL_ACC_A2]
    • decrease the Closed loop acceleration rate: [CL_ACC]

    Regarding the jolt during motor startup, what motor startup option [MTR_STARTUP] are you using?

    • if you are using Align or Double align, the initial movement is normal since the device will align the rotor to the align vector before it transitions into open loop acceleration
    • if this initial align movement is undesired, you could try using IPD as your motor startup option, which determines the initial rotor position by injecting high frequency current pulses that keeps the rotor stationary.
    • if the jolt is seen during open loop acceleration, you can try decreasing the [OL_ILIMIT] or [OL_DUTY] to apply a lower torque during open loop acceleration.

    Regards,
    Eric C.

  • 0
    Prodigy 100 points

    Ron,

    Ron Wilton said:
    Is it possible to get the motor to start up very slowly and gradually build up to the desired speed using a MCT8329A motor controller?

    For a slower speed ramp, try reducing your open-loop and closed-loop acceleration rates.  You may need to adjust your hand-off cycles, too.

    Ron Wilton said:
    I'm finding that the motor runs at a higher frequency before dropping down to the desired speed

    If your open-loop acceleration rate is too high relative to the maximum target speed, there's a chance that the motor will enter the closed-loop stage at an elevated speed.  The controller won't notice the elevated speed until it enters closed-loop, thus correcting the error (slowing the motor down).  Lowering your open-loop acceleration rate should fix this.

    Ron Wilton said:
    There is also a jolt as the motor starts up.

    The jolting action is likely happening during the alignment stage.  Decreasing your align voltage ramp and increasing the alignment time may solve this.