Originally Posted by
MurphyWasRight
Seems to me that an "inner loop" driving the control cylinder rate and/or position to the pilot/autopilot requested values would have to exist.
This is similar to using feedback around an op-amp to precisely set gain even though the raw gain of the amp may vary 10:1 or more.
You're right.
The "demand" to the innner loop (from the pilot or autopilot) is in terms of control surface position (angle), the feedback comes from a control surface position sensor.
If the available raw "gain" (hydraulic pressure) is too low then the inner loop will fail
Your analogy is wrong.... the hydraulic pressure does not equate to gain. To use your op-amp analogy, too low a hydraulic pressure would be similar to the supply voltage collapsing under load or the op amp output stage saturating.
... but that would represent either a fundamental design flaw/or hydraulic system failure.
Exactly.
Since we have a simpler explanation than hydraulic problems, I tend to apply Occams razor....
I am not familiar with real world details (work in electronics not hydraulics) so welcome insight from those who do know.
The transfer function for a electro-hydraulic actuator is a bit more complicated than a simple low-pass filter, but the suggestion of oscillations in the system is somewhat too far-fetched... and would indeed imply a fundamental design flaw.... The technology has been around too long, and is too well understood, for this to be a plausible cause, IMO.
CJ