Matlab绘制系统的根轨迹

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[mw_shl_code=applescript,true]%% g摄动时的参数根轨迹
clear;clc;close all;
%% 基本参数设定
Vpcc=311;  Rv=0.2180;  Xv=0.005;m=1e-4;Ei=306;
f = 50;  wn = 2*pi*f;  fh=0.2;wp=2*pi*fh;theta=90;
      
%% 求解零点极点和开环增益，并绘图
% for g=0.17e-3:0.01e-3:3.0e-3
  for g=1.408e-3:0.01e-3:6.438e-3
%     theta = 0: 2*pi/point_num:2*pi; %角度[0,2*pi]
    A=(Rv^2*Ei*Vpcc*sin(theta)-2*Rv*Xv*Ei*Vpcc*cos(theta)+2*Rv*Xv*Vpcc^2-Xv^2*Ei*Vpcc*sin(theta))/(Xv^2+Rv^2)^2;
    B=((Xv*cos(theta)-Rv*sin(theta))*Ei*Vpcc)/(Xv^2+Rv^2);
    C=((Rv^2-Xv^2)*Ei*Vpcc*cos(theta)+(Xv^2-Rv^2)*Vpcc+2*Rv*Xv*Ei*Vpcc*sin(theta))/(Xv^2+Rv^2)^2;
    D=-(Ei*Vpcc*Xv*sin(theta)+Ei*Vpcc*Xv*cos(theta))/(Xv^2+Rv^2);
    a=2*wp-C*g^2*wp;
    b=B*2*pi*m*wp-wp^2*C*g^2+wp^2;
    c=(A*D*2*pi*m*g^2+B*2*pi*m-B*2*pi*m*C*g^2)*wp^2;
%     d=2*pi*m*wp;
    p=[1 a b c];
    r=roots(p);
    p1=r(1);p2=r(2);p3=r(3);
%     i=1:1:100;
%     a(i,1)=z(1);a(i,2)=z(2);
%     a(i,3)=p(1);a(i,4)=p(2);a(i,5)=p(3);a(i,6)=p(4);
%     scatter(real(z1),imag(z1),'ko');%画出散点图
    scatter(real(p1),imag(p1),'mx');
    hold on;
    scatter(real(p2),imag(p2),'bx');
    hold on;
    scatter(real(p3),imag(p3),'kx');
    hold on;
    grid on;
end
% legend('z1','z2','p1','p2','p3','p4','FontSize',12); % 图形注释
% title('kp变化时参数根轨迹');
% xlabel('实轴 /s^{-1})','FontName','宋体');
% ylabel('虚轴 /s^{-1})','FontName','宋体');
set(gca,'fontsize',7);%图中所有字体设为10榜
set(gca,'box','on','linewidth',1)%图窗四边边框全显示，并设置1榜线型
% axis([-1000,50,-700,700])[/mw_shl_code]