%繪制根軌跡圖

disp('開環傳遞函數G(s)為：')
printsys(num1,den1,'s');
disp('反饋傳遞函數H(s)為:')
printsys(num2,den2,'s');
lcwin=figure('Position',[120 49 513 491],'Name','180度根軌跡圖','NumberTitle','off',...
      'MenuBar','none');

axes('position',[0 0 1 1]);
axis off;
dd=text(0.06,0.14,'系統穩定時K的范圍');
set(dd,'fontsize',15,'color',[0 0 0],'fontname','宋體');
numedit=uicontrol(lcwin,'style','edit','units','normalized','position',[0.45 0.1 0.2 0.1],...
        'fontsize',17,'back',[1 1 1],'max',10);
dd1=text(0.67,0.14,'到');
set(dd1,'fontsize',15,'color',[0 0 0],'fontname','宋體');
numedit1=uicontrol(lcwin,'style','edit','units','normalized','position',[0.75 0.1 0.2 0.1],...
        'fontsize',17,'back',[1 1 1],'max',10);

%設置繪圖區域
axes('Position',[.15 .33 .8 .56]);

%繪制根軌跡圖
sys1=tf(num1,den1)
sys2=tf(num2,den2)
sys3=series(sys1,sys2)
sys=feedback(sys1,sys2)
n1=num1(1,1)
n2=num2(1,1)
d1=den1(1,1)
d2=den2(1,1)
if n1<0&d1>0&n2>0&d2>0||d1<0&n1>0&n2>0&d2>0||n2<0&n1>0&d1>0&d2>0||d2<0&n1>0&d1>0&n2>0||...
    n1>0&d1<0&n2<0&d2<0||d1>0&n1<0&n2<0&d2<0||n2>0&n1<0&d1<0&d2<0||d2>0&n1<0&d1<0&n2<0
    msgbox('輸入范圍出錯','警告','warn')
else
    rlocus(sys3)
    %得出當系統穩定時K的取值范圍
    syms('x','w','k','real')
    num=conv(num1,num2)
    den=conv(den1,den2)
    n=poly2sym(k*num,x)
    d=poly2sym(den,x)
    f=n+d
    g=w*i
    h=compose(f,g)
    r=real(h)
    l=simplify(imag(h))
    [k,w]=solve(r,l)
    k1=sym2poly(k)
     if min(k1)<0
        set(numedit,'string',0)
    else
        set(numedit,'string',min(k1))
    end
     if max(k1)<0
        set(numedit1,'string',inf)
    else
        set(numedit1,'string',max(k1))
    end
end
ylabel('虛     軸');
xlabel('實     軸');
title('根軌跡圖');