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2 Example 8-6 OGATA 4ed(Bode plot)



    Let's plot Bode plot by Scilab.

    \begin{displaymath}G(s)=\frac{9\cdot (s^{2}+0.2\cdot s+1)}{s\cdot(s^{2}+1.2\cdot s+9)}\end{displaymath}

    Scilab program
    s=%s;
    s1=s/(2*%pi);
    g=9*(s1^2+0.2*s1+1)/(s1*(s1^2+1.2*s1+9));
    gs=syslin('c',g);
    clf;
    w=logspace(-2,3,100);
    bode(gs,w);
    xtitle('Bode plot of 9*(s^2+0.2*s+1))/(s*(s^2+1.2*s+9))');
    
    
    Image Ejemplo8-6bPag517


    Let's do it but according as program 8.4
    Scilab program
    s=%s/(2*%pi);
    g=(9*(s1^2+0.2*s1+1))/(s1*(s1^2+1.2*s1+9));
    gs=syslin('c',g);
    w=logspace(-2,3,100);
    gsf=tf2ss(gs);
    [frq1,rep] =repfreq(gsf,w);
    [db,phi]=dbphi(rep);
    clf;
    subplot(2,1,1);
    plot2d(w,db,style=0,logflag="ln")
    plot2d(w,db,style=2,logflag="ln")
    xgrid;
    mtlb_axis([0.01 1000 -50 50]);
    xtitle('Bode plot of (9*(s^2+4*s+25))/(s*(s^2+4*s+25))','frequency (rad/seg)',
    'Gain Db')
    subplot(2,1,2);
    plot2d(w,phi,style=0,logflag="ln")
    plot2d(w,phi,style=2,logflag="ln")
    xtitle('','frequency (rad/seg)','Phase (degrees)');
    mtlb_axis([0.01 1000 -150 150]);
    xgrid;
    
    Image Ejemplo8-6cPag521

cajael