ex4_22.m

华东理工大学自动化系《控制系统分析、设计和应用》教材配套程序实例,有关说明： 1. 安装MATLAB软件。安装时

% ex4_22
% 三阶环节的频率响应和衰减频率响应
figure('pos',[20,50,250,220],'color','w');
axes('pos',[0.2,.2,.7,.7]);
G=zpk([],[-1 -2 -3],6);
syms s m nums dens denm numm den num w;
G=tf(G);
num=poly2sym(G.num{1},s);
den=poly2sym(G.den{1},s);
m=0.221;
[MAG,PHASE,ww] = bode(G);
wM=max(ww)/10;
wm=min(ww);
w=logspace(log10(wm),log10(wM),100);
set(G,'inputdelay',0.5);
DT=get(G,'inputdelay');
numm=subs(num,s,(j-m)*w);
denm=subs(den,s,(j-m)*w);
nums=subs(num,s,j*w);
dens=subs(den,s,j*w);
Gm=numm./denm.*exp(m*w*DT);
Gs=nums./dens;
sysm=frd(Gm,w);
sys=frd(Gs,w);
set(sysm,'inputdelay',DT);
set(sys,'inputdelay',DT);
nyquist(sysm);
hold on;
nyquist(sys)
[Gmm,Pmm,Wcgm,Wcpm] = margin(sysm)