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DRV8301: How to Apply Break to the BLDC Maxon Motor

user4718777
Prodigy 50 points
Part Number: DRV8301

Hi, 

I have designed a BLDC driver Board using DRV8301, all is working fine i am able to drive the Max or any BLDC motor successfully at a rate velocity and position etc.

I am able to ramp up and run and ramp down the motor successfully no issues till now. Now this issue is, its a circular devices that runs around the pipe the motor is fitted on it, drive is able to run the motor in circular position along the pipe and stop at a give angle degree on the pipe. But no the issue is when i had any load on the device and try to stop the device just slips to the bottom of the pipe i.e 180 degree. 

How to solve this problem when there is a load applied, how do i hold the device at say 90 degree with 20kgs of load, without slipping,

Is there any breaking mechanism that i can adapt please guide.  

Regards

Mahesh Prasath.

  • 0
    TI__Guru** 114905 points
    Hi Mahesh,

    We will investigate and reply in a few days.
  • 0 in reply to Rick Duncan
    TI__Expert 4650 points
    Hi Mahesh,

    In order to hold the rotor of your BLDC at given angle the magnetic field of the stator must be holding the rotor at your desired angle. This will give you the required holding torque needed to keep your load at the desired angle.

    With a BLDC, this is often achieved using a three phase sinusoidal drive. When the rotor has reached the angle you would like to stop at, the three phases are energized so that the current flowing through each phase will hold the rotor at the desired angle.
  • 0 in reply to Phil Beard
    Prodigy 50 points

    Hi Phil,

    Thanks for your reply, I have another concern, should the duty cycle of all the three phase PWM remain 100%, please suggest.

    What should be low state of half bridge. quick response is appreciated. 

    Regards

    Mahesh Prasath.

  • 0 in reply to Phil Beard
    Prodigy 50 points
    Hi Phil,
    I tried the above method but still, the motor does not stop in the given angle, it just slides down the circle. Any other method suggest.
    What I did.
    Method 1 what we tried
    1) Enabled all the three phase high (100%) duty Cycle.
    2) Disabled all the low side of the Half bridge.
    when the motor is stopped.
    Method 2 What we tried:
    1) All high side of the half bridge with 0% Duty Cycle.
    2) Only Two phase of the low half bridge was energized.
    When the motor is stopped.

    But none of the both methods worked for us..

    Regards
    Mahesh Prasath
  • 0 in reply to user4718777
    TI__Prodigy 325 points

    Hi Mahesh,

    You can try different control technique (torque or speed control) instead of voltage control. Currently you are trying to brake the motor, but you should produce reverse holding torque to hold the load (20kg).

    In case of torque control set the reference torque zero to stop the motor. But due to load when motor will try to spin back then there should be negative current feedback. Due to current feedback (error) automatically PI controller will apply duty to hold the load. For faster PI response use higher integral gain(Ki).