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

2.1 Ripple Counting Algorithm Details

Ripple Counting Block Diagram Figure 2-3 Ripple Counting Block Diagram

Figure 2-3 shows the block diagram for the ripple counting algorithm. The dynamic nature of the commutation process, along with brushes, generates unwanted noise and causes distortion of the current ripple waveform. This unwanted noise in the current signal is filtered out using a digital filter. To improve accuracy, an error corrector block performs signal conditioning by adding or subtracting a set number of ripple counts to the result to compensate for over-counting or under-counting due to excessive noise in the system. The conditioned ripple output waveform is output through the RC_OUT pin in DRV8214 and DRV8234. The PI (Proportional-Integral) control loop generates the duty cycle command based on the difference between desired and detected values for speed or voltage regulation.