% Approximation of uncertain transfer function by unstructured
% multiplicative perturbation
%
hold off
omega = logspace(1,4,100);
%
% first-order fit
Wm = nd2sys([0.3803 60.8973],[1.0000 599.5829]);
Wm_g = frsp(Wm,omega);
K0 = 0.335; T0 = 0.002; 
Gnom = nd2sys([K0],[T0 1]);
Gnom_g = frsp(Gnom,omega);
for K = 0.9*K0:0.04*K0:1.1*K0
    for T = 0.8*T0:0.05*T0:1.2*T0
        G = nd2sys([K],[T 1]);
        G_g = frsp(G,omega);
        reldiff = vabs(vrdiv(msub(G_g,Gnom_g),Gnom_g));
        vplot('liv,lm',Wm_g,'r-',reldiff,'c--')
        hold on
    end
end
grid
xlabel('Frequency (rad/s)')
ylabel('Magnitude')
title('Approximation of the transfer function of the second actuator')
%legend('|Wm(j\omega)|',...
%       '|(G(j\omega)-G_{nom}(j\omega))/G_{nom}(j\omega)|',3)
hold off