%
% Critério de Nyquist MIMO
%
% SEM 5928 - Sistemas de Controle 
% Escola de Engenharia de São Carlos - USP
%
% Adriano Siqueira - 2016
%

clear all
close all
clc

A=[1 4;2 3]
B=[1 0;0 1]
C=[1 2;0 1]

lambdaMA = eig(A)
figure(1)
hold on
grid

figure(2)
hold on

for K = .1:.2:3;
K
lambdaMF = eig(A-B*K*C)

j=1;
for w=0.01:.1:100

Det = det(eye(2) + K*C*inv(eye(2)*i*w - A)*B);
    
R(j) = real(Det);
I(j) = imag(Det);

j=j+1;
end
figure(1)
plot(R,I)
plot(R,-I)
axis([-1.5 1.5 -1.5 1.5]) 
plot(R(1:10),I(1:10),'g')

n= [1 (2*K-8) (K^2-8*K+6) (40-10*K-4*K^2) (25-5*K^2)];
d= conv([1 -4 -5],[1 -4 -5]);

DetG = tf(n,d);
figure(2)
nyquist(DetG)
axis([-4 1.5 -1.5 1.5])

pause
end