@Machinbird,
Pardon. " As we know, the transcription of the acronym "PIO" has been modified and is still unfixed so long the solutions to avoid and recover from a variety of "oscillations" are still to fix and understand better. My propositions are leading too far of common definitions of theory of systems. I don't want to contest them (instability, gain, human operator transfer function). I have to write that clearer.
