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

3.3 Robotic Wheel Motor with Ripple Counting

The tuned parameters can be found in Table 3-5. Please assume default values for the writable register values not mentioned. Please note that it is advisable to turn on the error corrector (DIS_EC=0b) only while PWM-ing since current waveform is noisy.

Table 3-5 Tuned Parameter Values for the Vacuum Robot Wheel Motor
Parameter/Register Bits/Decimals Value
EN_RC 1b -
W_SCALE 01b 32 rad/s
INV_R_SCALE 10b 1024
INV_R 0x66 102
KMC_SCALE 01b 24 × 29
KMC 0xFC 252
FLT_GAIN_SEL 11b 16
FLT_K 0110b 6
Note:

The following sections demonstrate the performance of the ripple counting algorithm in various situations. Please note that:

  1. RC_OUT output is denoted in yellow.
  2. Motor current is observed using a current probe and shown in green.
  3. Encoder output is shown in pink.
  4. Accuracy, is calculated against the output of an encoder. Encoder emits 4 pulses per rotation. RC_OUT emits 6 counts per rotation. Thus, accuracy can be calculated using the following equation:
Equation 5. Accuracy=No. of RC_OUT counts6No. of encoder counts4×100%