PID Tuning

OrniFlight uses a PID (Proportional-Integral-Derivative) controller adapted for flapping-wing flight. Tuning differs significantly from conventional aircraft due to the periodic nature of flapping thrust.

Ornithopter PID Basics

Unlike conventional aircraft where thrust is nearly continuous, ornithopter thrust oscillates with each wing stroke. This creates:

Thrust ripple at flapping frequency (typically 5–15 Hz)
Phase-dependent control authority — same PID output has different effect depending on where in the stroke cycle it’s applied
Coupled roll-yaw dynamics — asymmetric wing thrust affects both axes simultaneously

PID Terms

Term	Effect	Ornithopter Note
P	Proportional — immediate correction	Use conservative values; oscillation is flapping-synchronous
I	Integral — persistent error correction	Essential for maintaining attitude during glides
D	Derivative — dampens oscillations	Tuned to wing stroke rate, not frame oscillations
F	Feed-forward — direct stick-to-output	Useful for crisp response on roll axis

Starting Values

For a medium-sized ornithopter (1–1.5m wingspan):

Axis	P	I	D	F
Roll	25	30	15	30
Pitch	30	35	20	35
Yaw	40	35	10	20

Tuning Procedure

1. Rate Tuning First

Before PID tuning, set rates that feel comfortable: - Start with RC Rate 0.90, Super Rate 0.65, Expo 0.30 - Adjust for your flying style and ornithopter size

2. P Gain

Increase P until you see oscillation at flapping frequency, then back off 20%: - Roll oscillation: wing wobble at stroke rate - Pitch oscillation: fore-aft bobbing - Yaw oscillation: tail wag synchronized with strokes

3. D Gain

Increase D to dampen bounce-back after sharp stick inputs: - Too much: servo jitter, overheating - Too little: ringing after roll/pitch stops

4. I Gain

I gain counters persistent drift: - Increase until drift is eliminated - Too much: slow oscillation at 1–2 Hz (below flapping rate)

ONDAS Integration

ONDAS (Ornithopter Nonlinear Dynamic Aerodynamic System) modulates the PID output within each wing stroke. After basic PID tuning:

Set Cadence Gain — shifts modulation window to aerodynamically optimal phase
Set Ferocity P — immediate asymmetric thrust boost
Set Ferocity D — anticipatory drag exploitation
Fine-tune Balance — left/right wing symmetry

See ONDAS Tuning Guide for detailed procedure.

Blackbox Analysis

Enable Blackbox logging to visualize PID performance. Look for: - P-term oscillation at flapping frequency → reduce P - I-term windup during sustained turns → reduce I or increase I-term relax - D-term noise from vibration → check mechanical balance first, then reduce D

Flight Profiles

OrniFlight supports 3 flight profiles switchable mid-flight:

Profile	Use Case
1	Standard cruise
2	High agility / aggressive
3	Efficiency / thermal soaring