ex8_14.m

反馈控制系统设计与分析（matlab程序）

num=400; den=[1,2,400];  G=tf(num,den);
        nW1=100*conv([0.005,1],[0.005,1]); dW1=conv([0.2,1],[0.2,1]);
        nW3=[1,0,0]; dW3=[40000];
        [m1,p1,w1]=bode(tf(nW1,dW1)); 
        semilogx(w1,20*log10(m1(:)))
        figure, [m3,p3,w3]=bode(tf(nW3,dW3)); 
        semilogx(w3,20*log10(m3(:)))
        
        [a,b,c,d]=tf2ss(num,den); S=mksys(a,b,c,d); 
W1=[nW1; dW1]; W3=[nW3; 0,0,dW3];
TSS_=augtf(S,W1,[],W3);

[cF1,ccL]=hinf(TSS_);

[af,bf,cf,df]=branch(cF1); Gc=zpk(ss(af,bf,cf,df))

G_o=G*Gc; G_c=feedback(G_o,1); step(G_c)

dW1=0.5*dW1; W1=[nW1; dW1]; TSS_=augtf(S,W1,[],W3);
[cF2,CL2]=hinf(TSS_);  [af,bf,cf,df]=branch(cF2);
F1=ss(af,bf,cf,df); G_o=tf(num,den)*F1;
G_c=feedback(G_o,1); step(G_c)
zpk(F1)

delta=-10:1:10; f1=figure;  
f2=figure; ngrid('new')
for i=1:length(delta)
   den(2)=delta(i); G=tf(num,den);
   G_o=G*F1; G_c=feedback(G_o,1);
   figure(f1); step(G_c), hold on
   figure(f2); nichols(G_o); 
end
figure(f1); set(gca,'Xlim',[0,0.2])
figure(f2), set(gca,'Xlim',[-360,0],'yLim',[-40,40])