• State Resolved
  • +1 person also asked this people also asked this
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 39 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

DRV8462: Closed loop control with Encoder to dynamically change full scale current depending on load

Visaacan Rathiraj
Prodigy 80 points
Part Number: DRV8462

Tool/software:

Hi Team,

Our team would love to speak with an applications engineer via online call that could answer some questions we have regarding closed loop control of the DRV8462 and a magnetic encoder using the HW interface of the DRV

Regards,
Visaacan

  • 0
    TI__Mastermind 31495 points

    Hi Visaacan,

    Thank you for you interest with the DRV8462 as well as posting your question in this forum. The DRV8462 does not have an HW interface to talk to and work with an magnetic encoder. It is an open loop only stepper driver. However the controlling MCU could interface with the external magnetic encoder for closed loop position control.

    In the title you mentioned "dynamically change full scale current depending on load". This can be done with the built-in feature of the device known as auto-torque in SPI control mode without any additional external components. This is described in section 7.3.14 Auto-torque Dynamic Current Adjustment of the datasheet from page-41 as well as in this application note, https://www.ti.com/lit/an/slvaff1/slvaff1.pdf. This feature can be evaluated using one of our DRV8462EVM. Please review these and let us know if any questions. I'm the subject matter expert and application engineer for our stepper drivers portfolio. I can address any questions regarding the DRV8462 via this forum. Thanks.

    Regards, Murugavel     

  • 0 in reply to Murugavel4637
    Prodigy 80 points

    Hi  Muruagavel,

    Yes sorry I was not clear about how everything would be interfaced the plan is to use the HW interface of the DRV8462 (STEP and DIR pins) with an external MCU and the MCU would be communicating with an magnetic encoder to get position data.

    One question I had was without using the auto torque feature do you think it is possible to do something similar using the STEP and DIR interface and dynamically adjusting VREF based on encoder data to the MCU, is there other things that we need to consider trying to do an approach like this? 

    Thanks for the support,
    Visaacan

  • +1 in reply to Visaacan Rathiraj
    TI__Mastermind 31495 points

    Hi Visaacan,

    Thank you for the clarification. 

    Visaacan Rathiraj said:
    One question I had was without using the auto torque feature do you think it is possible to do something similar using the STEP and DIR interface and dynamically adjusting VREF based on encoder data to the MCU

    Yes, you can do this. Changing VREF will change the IFS full-scale current setting. It can be changed dynamically. You want to consider to change VREF at full electrical cycles or half electrical cycles of the current waveform, ideally at the zero crossing. This can be done by keeping track of the number of step pulses which is usually done in the MCU anyways. For example with microstepping current would be a sine wave. Changing VREF at zero crossing would reduce the mechanical artifacts from the motor movement. Thanks.

    Regards, Murugavel