Gain compression
main (planned for: PX4 v1.17)Automatic gain compression reduces the gains of the angular-rate PID whenever oscillations are detected. It monitors the angular-rate controller output through a band-pass filter to identify these oscillations.
This approach is a safe adaptive mechanism for stable aircraft: the PID gains remain unchanged when no oscillations are present, they are never increased beyond their nominal values, and they are bounded by a minimum limit.
Gain compression can help prevent actuator damage and even loss of the vehicle in cases such as airspeed-sensor failure (loss of airspeed scaling) or in-flight changes in dynamics (e.g.: CG shifts, inertia changes), or other failures that could cause the angular-rate loop to become oscillatory.
Usage
Gain compression is enabled by default (FW_GC_EN).
It should be disabled during fixed wing manual tuning to avoid over-tuning. It does not need to be disabled when autotuning.