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DRV8711: Tuning Steps, How to Setup Suitable Configurations and Get a Nice Sinusoidal Current Waveform

Kim Wang
Prodigy 10 points
Part Number: DRV8711

Questions:

  1. How to achieve a low noise performance of stepper?
    1. What impacts noise of a running stepper?
    2. Which drv8711 driver configurations impact noise?
  2. How to achieve a minimal vibration performance of a stepper?
    1. What causes vibration of a running stepper?
    2. Which drv8711 driver configurations impact vibration?
  3. Are the below current waveforms expected?
    1. Do higher frequencies cause triangular/square current waveforms?
    2. Can we set configurations such that the current waveforms are sinusoidal for all ranges of speed (1Hz to 250kHz)?
  4. For accelerating and decelerating the stepper, do we need a non-zero starting speed and stopping speed?
    1. Why?
  5. Why powering on motor (setting enable on CRTL Register of DRV8711) makes the motor jump/jerk?

My setup configuration is as follow:

  1. Stepper Motor: Bipolar Stepper Motor Frame Size 23 200.0 Step 2.8 A 24VDC
  2. Power Supply: 48V
  3. DRV8711EVM board
  4. Using most of the recommended settings from DRV8711 Quick Spin and Tuning Guide: 
    • Register Hex Value Settings
    • 0x01 Torque 0x0180  Torque = 80
    • 0x02 Off 0x0032 Internal indexer, 25 µs off time
    • 0x03 Blank 0x0100 Adaptive blanking, 1-µs current blanking
    • 0x04 Decay 0x0510 Use auto mixed decay, mixed decay time has no effect.
    • 0x05 Stall 0x0A02 BEMF/8, Stall after 2, approximately 20 mV (without experimentation yet)
    • 0x06 Drive 0x0000 Minimal drive, minimum OCP deglitch and threshold
    • 0x00 Control 0xxxxx 850 ns dead time, gain of 10, internal stall detect, 1/128 step, enable motor

One winding current waveform are measured below at varying indexing speeds:

Period = 1000 us

Period = 100 us


Period = 10us

  • 0
    Prodigy 10 points

    Follow-Up:

    Updated Winding Current Waveform at stepping frequency of 1kHz (period = 1000 us). 
    The change was increasing the following:

    • tBLANK
    • 0x03 Blank 0x01D8 Increase to 4.32-µs current blanking (from 1us) 

    Better sinusoidal waveform. Less vibrating but has a high pitch chirp sound. Doesn't sound like right behavior.  

    Question:

    1. How to decrease the higher pitch chirp sound?
    2. Why are these behavior?
      1. Higher chirp
      2. Less vibrating (pounding table sound)


  • 0 in reply to Kim Wang
    TI__Mastermind 23000 points

    Hey Kim,

    Kim Wang said:
    • How to achieve a low noise performance of stepper?
      1. What impacts noise of a running stepper?
      2. Which drv8711 driver configurations impact noise?
    • How to achieve a minimal vibration performance of a stepper?
      1. What causes vibration of a running stepper?

    See this app note - How to Reduce Audible Noise in Stepper Motors, I think it will answer all of these questions. 

    Kim Wang said:
    Are the below current waveforms expected?
    1. Do higher frequencies cause triangular/square current waveforms?
    2. Can we set configurations such that the current waveforms are sinusoidal for all ranges of speed (1Hz to 250kHz)?

    Please see this app note, DRV8711 Decay Mode Setting Optimization. 

    Would you mind looking through those and let me know which questions you still have?

    On the motor noise/chirp, can you give either a motor datasheet/model or the key specs like resistance and inductance of it?  

    Lastly, do you have a DRV8711EVM that you are testing this on, or is it on your own PCB?  

    Best,

    Jacob

  • 0 in reply to Jacob Thompson
    Prodigy 10 points

    Hey Jacob,

    Thanks for the resources. 

    To reply:

    1. The motor I am currently using is the WO-5718L-01P-RO LIN ENG. 
      1. Resistance 1.1 Ohms/Phase
      2. Inductance not known
    2. I am using TI's DRV8711EVM board: https://www.ti.com/tool/DRV8711EVM

    Additional questions for DRV8711 Decay Mode Setting Optimization: 

    1. Is every parameter change simply experimental? Or is there a calculation that can be done to figure out what combination of the parameters tunings can get the most optimized result with the least side effects. 
  • 0 in reply to Kim Wang
    TI__Mastermind 23000 points

    Hey Kim,

    Okay, good to hear you have the EVM to test with! 

    Kim Wang said:
    Is every parameter change simply experimental? Or is there a calculation that can be done to figure out what combination of the parameters tunings can get the most optimized result with the least side effects. 

    Basically experimental, yes.  There are some generalities we can make, but no calculation for the absolute best.  Often there will be tradeoffs of audible noise vs EMI noise vs mechanical noise, and the cleanest waveform doesn't necessarily produce the quietest result.  So yes, it is experimental in nature unfortunately.  In my experience, you want to use the highest microstep setting that can accomplish your torque/speed/acceleration needs.  1/256 microstep will typically be much quieter than 1/4 microstep.  But that's just testing and determining what is the best. 

    What's the required current of your motor?  We have a recently released DRV8462 which is an integrated stepper motor driver for up to 5A full-scale current in DDW package, and 10A in soon to be released DDV package.  If this could drive your load it would give you many more advanced features including Silent Step and Auto-Torque, and have a much smaller PCB footprint than DRV8711+FETs. 

    Regards,

    Jacob