SLVAFO8A April   2024  – May 2024 DRV8214 , DRV8234

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction: Need for Sensorless Designs
  5. 2Ripple Counting − Concept
    1. 2.1 Ripple Counting Algorithm Details
  6. 3Case Study: Robotic Wheel Drive
    1. 3.1 Robotic Wheel Motor Operating Conditions
    2. 3.2 Tuning Parameters for Ripple Counting
      1. 3.2.1 Resistance Parameters
      2. 3.2.2 KMC and KMC_SCALE
        1. 3.2.2.1 Tuning KMC_SCALE
        2. 3.2.2.2 Tuning KMC
    3. 3.3 Robotic Wheel Motor with Ripple Counting
      1. 3.3.1 Inrush and Steady State Performance
        1. 3.3.1.1 Motor Speed Calculation
      2. 3.3.2 Soft Start
      3. 3.3.3 Loaded Conditions
  7. 4Challenges and Workarounds
    1. 4.1 Low Average Currents
    2. 4.2 Motor Inertia During Stop
    3. 4.3 Inrush
    4. 4.4 High Load Conditions
  8. 5Summary
  9. 6References
  10. 7Revision History

3.2.2.2 Tuning KMC

  1. From section 8.2.3.1.2.2.1.2 in the data sheet, the first step to tune KMC is to verify that EST_SPEED < OBS_SPEED and value of KMC is 255. If this is not the case, please restart the tuning process.
  2. Following the next steps from the data sheet, we find that the tuned value of KMC is 32. Figure 8-4 (Binary Search Algorithm to Find KMC) in the DRV8234 data sheet displays a flowchart for tuning KMC using the Binary Search Algorithm. The iterative steps for tuning KMC in this example are summarized in Table 3-4,
Table 3-4 KMC Tuning
Iteration KMC_SCALE KMC START MID END EST_SPEED (rad/s) OBS_SPEED (rad/s) Decision
1 10b 1 1 128 255 4080 3770 EST>(OBS+16)
2 10b 128 1 64 128 960 3770 EST<(OBS-16)
3 10b 64 1 32 64 1920 3770 EST<(OBS-16)
4 10b 32 32 48 64 3776 3770 EST within OBS±16