ex6_4.m

反馈控制系统设计与分析（matlab程序）

G=tf(100,[conv([1,1],[0.0125,1]),0]);
Gc=leadlagc(G,50,50,100); zpk(Gc)

G_o1=Gc*G; w=logspace(0,4); ngrid('new'); 
nichols(G,w); nichols(G_o1,w), axis([-360,0,-40,40])

Gc=leadlagc(G,50,90,100); zpk(Gc)

G_o2=G*Gc; ngrid('new');
nichols(G,w); nichols(G_o2,w), axis([-360,0,-40,40])
[G1,P1,w1,w2]=margin(G_o2); [G1,P1,w1,w2]

Gc=leadlagc(G,100,50,100); zpk(Gc)

G_o3=G*Gc;  ngrid('new'); 
nichols(G,w); nichols(G_o3,w), axis([-360,0,-40,40])
[G1,P1,w1,w2]=margin(G_o3); [G1,P1,w1,w2]

G_c1=feedback(G_o1,1); G_c2=feedback(G_o2,1); G_c3=feedback(G_o3,1);
[y1,t]=step(G_c1); y2=step(G_c2,t); y3=step(G_c3,t);
plot(t,[y1,y2,y3])