ONDAS — Oscillating Normalized Dynamic Adaptive Stabilization
The Core Principle
A fixed-wing or conventional aircraft generates control forces continuously — a control surface deflection or RPM change produces a steady-state moment. An ornithopter does not. Every gram of thrust, every Newton of torque, is phase-bound within the wingbeat cycle. The same force impulse applied at different points in the stroke produces fundamentally different results.
ONDAS acknowledges this reality and modulates stabilization effort synchronously with the flapping cycle.
Cadence — The Timing Brain
Cadence is the most critical ONDAS filter because it determines when correction happens within each wingbeat.
| Stroke Phase | Effect of Force Application |
|---|---|
| Downstroke center | Maximum lift, roll authority |
| Downstroke end (braking) | Induced drag → yaw moment |
| Upstroke center | Thrust rearward, pitch-up |
| Upstroke end | Wing reversal, minimal effect |
Cadence shifts the modulation window to align with the phase where the aerodynamic lever arm is longest. Wrong cadence = fighting wing physics. Correct cadence = every milliwatt becomes control authority.
Parameters
| Parameter | Value | Function |
|---|---|---|
ONDAS_K0 |
1.0 | Base phase offset |
ONDAS_K2 |
10.0 | Phase spread / sharpness |
ONDAS_PHASE_SCALE |
0.00005 | Small factor, large leverage |
Ferocity P — Immediate Asymmetric Thrust
Ferocity P increases the waveform squareness (trapezoidal shaping: dwell at ±1, cosine ramp between) proportionally to the current PID error.
- More thrust on one side → immediate moment
- The braked wing at stroke-end experiences induced drag — this is the counter-moment
- Effect: direct, proportional, immediate
Ferocity D — Anticipatory Drag Exploitation
Ferocity D completes the picture. Where P provides thrust asymmetry, D leverages the drag of the contralateral wing as a brake.
- Reads error rate of change and anticipates
- Can deliberately exploit the drag of a slowed wing for yaw/pitch moments
- P+D together create a differential moment pair — thrust on side A, drag on side B — more efficient than thrust-only
Three Ways Cadence/Ferocity D Increases Ferocity
1. Direct — D boosts P during rapid error change
In gusts or aggressive maneuvers, error_rate is large. D multiplies this and adds to base ferocity. The wing becomes sharper (more trapezoidal) because P+D together demand more squareness than P alone. Result: maximum authority precisely when critical.
2. Indirect — Cadence shifts the leverage point
Cadence modulates when in the cycle ferocity acts. Moving the window into a more aerodynamically sensitive phase (e.g., downstroke center vs. upstroke end) means the same ferocity value produces more effect — effectively amplification without numerical change.
3. Combinatorial — D × Cadence during stall recovery
In a stall: high sink rate → D detects the rate → increases ferocity. Simultaneously, cadence shifts modulation into the downstroke phase where the wing has maximum bite. The interplay: D provides the force, cadence the right moment. Without cadence, D-force arrives at the wrong phase and dissipates uselessly.
Additional ONDAS Parameters
| Parameter | Function |
|---|---|
| Balance | Up/down thrust symmetry — I-term bias between upstroke and downstroke. Compensates for wing asymmetry, manufacturing tolerances, and wear |
| Warp | Roll/Yaw P → L/R ferocity differential — right and left wings flap independently on the roll axis for bank and turn maneuvers |
| Anchor | Phase anchoring — locks modulation to a specific phase reference, resisting drift |
| Resonance | Airframe resonance compensation — avoids exciting structural modes of the airframe |
Analogy
Cadence is the conductor. Ferocity P and D are the instruments.
Without a conductor, they play — but not together. With one, noise becomes music.
See Also
- ONDAS Tuning Guide — practical tuning procedure
- MSP Protocol — wire format for ONDAS parameters
- Flight Profiles — profile-aware ONDAS configuration