The first plot confirms that the open-loop response has integral action and the desired
gain crossover frequency while the second plot shows that the MIMO stability margins
are satisfactory (the blue curve should remain below the yellow bound). Next check the
response from the step command azref to the vertical acceleration az:
T = getIOTransfer(ST,'az ref','az');
figure
step(T,5)
The acceleration az does not track azref despite the presence of an integrator in the
loop. This is because the feedback loop acts on the two variables az and q and we have
not specified which one should track azref.
Tuning of a Two-Loop Autopilot