Filters and PID tuing in Betaflight

How I tune filters and PIDs in Betaflight using PIDtoolbox pro (a musthave)

radio

• ADC Filter OFF
• global functions -> GF1 ON Lua Script bfbkgd for time sync from radio’s RTC to the betaflight flight controller

quad

• must have a capacitor
• must have new props installed, all screws tightened, no dangling antennas or XT60

ESC

• ESC tuning
• https://esc-configurator.com or https://am32.ca, or locally
• for 2,5-inch and smaller set PWM frequency to 48 kHz, for larger quads set it to 24 kHz
• set type to 2S+ if it is not 1S FC, disable temperature protection
• motor settings in am32 must be set close to the actual ones. manual protocol selection DSHOT

Betaflight preparation

• backup previous config (dump and diff all showdefaults), flash the latest version of Betaflight using online app or locally
• load ELRS profile, racing preset
• load defaults: tune + filters profile, if available for the current BF version
• enable bidirectional dshot, set correct dynamic idle value is based on the prop size/pitch, here and here
• the two pidsum_limit can be used to set PID authority to 100% from 50% default (do not change this after PID tuning).

  set pidsum_limit = 1000
  set pidsum_limit_yaw = 1000
  

• if MCU has enough compute power, set ESCs to DSHOT600, set pid_process_denom = 1 and disable gyro low pass 2
• motor_poles must be set correctly (usually 12 for small motors and 14 for large motors)
• set blackbox to 2 kHz

Filters

• https://www.youtube.com/watch?v=E3s5XYk3M74
• UAVTech’s workspace for blackbox viewer is here
• adjust

  set rpm_filter_weights = 100,20,20
  set rpm_filter_fade_range_hz = 0
  set rpm_filter_q = 500
  

PID

• https://www.youtube.com/watch?v=sqT4MACi3d8
• https://www.youtube.com/watch?v=ehvQm8Rqrzk
• set angle to 100
• the process
  • on the default PIDs, record hover
  • use blackbox explorer and PIDtoolbox to adjust the filters
  • set ff and dmax to zero, iterm gain to 0.2
  • in angle mode, record wiggle with dterm gain 0.6-1.8 step 0.2, set the best curve without overshoot (to have a headroom for mm)
  • in angle mode, record wiggle with master multiplier 0.6-1.8 step 0.2, choose loweset latency, compare roll and pitch latency and adjust roll:pitch balance
  • in acro mode, record iterm gain 0.5-2 step 0.5, choose the lowest latency between setpoint and gyro
• if there is a slow bounceback after a roll or a flip, lower I term gain
• iterm https://www.youtube.com/watch?v=Sq_DFjmvVDE

after tuning

• turn on anti-gravity, voltage sag compensation (depends on vbat_warning_cell_voltage), thrust linearization
• set motor_output_limit = 90 for a 5-inch

problems

• about the washout problem with ducted frames, when quad not descending with lowered throttle
• hot motors 1 2 . Too Much D-Term, Too Little Filtering, or Both

references

• https://oscarliang.com/fpv-drone-tuning/
• https://oscarliang.com/pid/
• https://www.youtube.com/playlist?list=PLFPBjpbd5xKQAzyblBStGKYtNdP9FCpRe