Betaflight 4.5 Tuning Masterclass - Video 2: PIT Tuning Notes

Introduction

• Second video in Betaflight 4.5 tuning series.
• First video covered filters; essential for pit tuning.
• Structured approach: start with basic, progress to advanced.
• Goal: improve quad tuning progressively.

Overview of PID Controller

• Inputs:
  • Set Point: position of the sticks.
  • Gyro: measures rotational rate on all axes.
• PID Error: difference between set point and gyro output.
• Terms:
  • Proportional (P): reduces PID error to zero.
  • Integral (I): sums up error over time.
  • Derivative (D): reacts to rate of change in gyro.
  • Feed Forward: anticipates stick movement.

Individual PID Terms

Proportional (P) Term

• Acts like a spring in a suspension strut.
• Increases with PID error to reduce it to zero.

Derivative (D) Term

• Acts like a shock absorber.
• Prevents overshoots and oscillations by dampening response.

Integral (I) Term

• Accumulates error over time, pushes harder to minimize steady-state error.
• Balances with P term to avoid oscillations.

Tuning Flights

• Perform sharp moves on roll, pitch, yaw axes.
• Keep hold of sticks during moves to collect clean data.
• Consider tuning in angle mode for easier control.
• Optional: increase PITM Limit for responsiveness (e.g., set pitm_limit=1000).

Tuning Process

1. Master Multiplier:
   • Tune like adjusting volume.
   • Set according to build conditions (e.g., GoPro on).
   • More powerful motors may require lower multiplier.
   • Observe motor temperature and sound during flights.
2. Dynamic Damping:
   • Set to zero initially for tuning.
   • Adjust master multiplier from 0.5 upwards.
   • Monitor for motor sounds and temperatures.
3. PID Balance:
   • Disable feed forward and I terms to tune PD balance.
   • Adjust P and D sliders, looking for oscillations.
   • Use Blackbox logs to analyze response.

Tuning I Term

• Tuning Method:
  • Start with low I gain; increase until oscillations appear.
  • Adjust based on precision and accuracy in flight.
• Settings:
  • Consider using Iterm Relax and Iterm Wind Up to manage accumulation during fast moves.
  • Fine-tune with throttle behavior.

Advanced Tuning Topics

• Feed Forward:
  • Adjust for responsiveness; too high can cause overshooting.
  • Use Blackbox for analysis of stick tracking.
• Dynamic Damping:
  • Adjust for sharp moves vs. normal flight.
  • Can help with overshoot from high feed forward.
• Throttle Boost and Motor Output Limit:
  • Adjusts throttle response and limits motor drive for different battery setups.
• VBat Sag Compensation:
  • Alters motor drive based on battery voltage for consistent performance.
• Thrust Linearization:
  • Boosts low throttle torque for better responsiveness.

Conclusion

• Final tuning results in a quad tightly locked to sticks.
• Next video will cover tuning rates for smoother stick feel.
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