Originally Posted by
Check Airman
If I’m understanding what you guys are saying, these diagrams are just explaining how the roll rate is generated, and not necessarily what the stick/surface relationship is. Is that right?
More or less yes. Airbus use a roll rate control law, though that's not what the loop is really controlling:
What you input with the stick is first integrated (rate to angle conversion) and the loop controls the roll angle. That's why in gusts the aircraft always returns to the last roll angle (as long as you don't make control inputs). That's not all: there is also a direct input from stick to the roll angle loop. If you want so a type of Phi pre command. Conversion from dPhi to Phi consequently is realized with a P-I element (in terms of control loop design). There are multiple reasons for the PI combination: Roll angle feedback with Phi>33 (AC returns always to 33 when no input = positive spiral stabillity), a "good feeling" (minimizing PIO risk) for the pilot as the AC directly reacts to stick input and so on....
In the Phi loop you have the coupling between yaw and roll and there a deflection command is generated. This command is fed through the kinematics (which is nothing more than different LUTs for different configuration) and out of them (with rate limiting most likely applied afterwards) you get the commands for the surfaces.
BUT: I have to ask, but I'm pretty sure that there is also a LUT between stick in and stick command used for the law. That's how one could realize a different sensitivity for different configurations.
Simon