This Bode plot suggests that the diagonal terms behave as integrators (up to the sign)
beyond 5 rad/s. This justifies using proportional-only control. Consistent with the baseline
design, set the target bandwidth for the p,q,r loops to 30, 22.5, and 37.5 rad/s,
respectively. The gains Kp, Kq, Kr for each (alpha,beta) value are readily obtained from
the plant frequency response at these frequencies, and the phase plots indicate that Kp
should be positive (negative feedback) and Kq, Kr should be negative (positive feedback).
% Compute Kp,Kq,Kr for each (alpha,beta) condition. Resulting arrays
% have size [1 1 8 5]
Kp = 1./abs(evalfr(Gpqr(1,1),30i));
Kq = -1./abs(evalfr(Gpqr(2,2),22.5i));
Kr = -1./abs(evalfr(Gpqr(3,3),37.5i));
Angular Rate Control in the HL-20 Autopilot