sgrid1.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

function sgrid1(nn,fre)
%zeta=[0.216 0.344];fre=[1:5];
% 根据阻尼比回衰减比和频率绘制等阻尼比线和等频线

% Copyright 2000-2001 ECUST. 
%   $Revision: 1.2 $  $Date: 2001/04/12 16:48:42 $

if nn>1,syms zet n pp;pp=subs((n-exp(2*pi*zet./sqrt(1-zet.*zet))),'n',nn);
for i=1:length(nn),zea(i,:)=solve(pp(i)),end;zeta=sym2poly(zea);else zeta=nn;end;
bs=sqrt(1-zeta.*zeta)./zeta;YM=max(get(gca,'ylim'));ym=min(get(gca,'ylim'));
XM=max(get(gca,'xlim'));xm=min(get(gca,'xlim'));xs=(ym+0.025*(YM-ym))./bs;
for i=1:length(fre);t=-pi/2:0.01:pi/2;
    x=-fre(i)*cos(t);y=fre(i)*sin(t);plot(x,y,':');yy=fre(i)-0.025*(YM-ym);
    if ym<yy & yy<YM;text(-0.025*(XM-xm),yy,num2str(fre(i)),'fonts',8);end;
    hold on;end;h=get(gcf,'pos');
for i=1:length(zeta);
    line([0 xm],[0 bs(i)*xm],'lines',':','col','k');
    line([0 xm],[0 -bs(i)*xm],'lines',':','col','k');
    if h(3)<=350 |h(4)<=300,
    text(xs(i)+(0.025+(i-1)*0.008*bs(i))*(XM-xm),ym+(0.025+(i-1)*0.05)*(YM-ym),num2str(zeta(i)),'fonts',8);
    else text(xs(i)+0.025*(XM-xm),ym+0.025*(YM-ym),num2str(zeta(i)),'fonts',8);end;
end;