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MCT8316A: PI Speed Control

Unai Canales
Prodigy 40 points
Part Number: MCT8316A

Tool/software:

Hi,

We are currently evaluating the MCT8316A motor controller and we have encountered a limitation with the integrated PI speed controller for our application. We understand that the available gain ranges are:

  • Kp: from 0 to 0.1023
  • Ki: from 0 to 0.004095

These constraints prevent us from achieving the desired dynamic response from the motor. As a result, we are considering implementing the PI speed control externally using a separate microcontroller.

However, we have some concerns regarding the internal acceleration and deceleration rate limitations of the MCT8316A, which we believe might interfere with the external control loop.

We would appreciate your guidance on the following points:

  1. Is it possible to implement an external PI speed controll in a external microcontroller using MCT8316A?
  2. What are the recommended settings for acceleration and deceleration rates to ensure minimal impact on the external control loop?
  3. Are there any additional considerations or best practices we should follow to ensure stable and responsive motor behavior under external PI control?

Thank you in advance for your support. We look forward to your recommendations.

Regards

  • 0
    TI__Mastermind 23222 points

    Hi Unai,

    I will respond by this weekend.

    Thanks and Best Regards

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    Prodigy 40 points

    Hi Venkatadri,

    I haven’t received a response yet.

    Let me know if you need more information.

    Best regards.

    Unai C

  • 0 in reply to Unai Canales
    TI__Mastermind 23222 points

    Hi Unai C,

    Sorry for late response. 

    1. We can use external PI if the PI gain is not sufficient for your application. The acceleration / deceleration factor depends on the inertia, available power (dc bus current, voltage). Most of the case the PI gain available is sufficient, verify with Voltage mode if the acceleration is achievable and then test with speed loop enable

    2.  CL_ACC is V/s, the duty is output of PI loop. The ramp of duty from reference to next reference is controlled through the CL_ACC value. Basically, we should match the resolution between external loop and internal loop.

    3. External loop has to sample the speed (via I2C/FG) and then process the duty command. Account the loop latency when using the external speed especially for transient conditions.

    Go through modelling to understand feasibility of the approach.

    Thanks and Best regrads

    Venkatadri S