[Scilab-users] Problems with Bode and Bode asymptotic

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Emmanuel Delaleau Emmanuel Delaleau
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[Scilab-users] Problems with Bode and Bode asymptotic

I don't succeed in using the Bode plots facilities. (See script below).

- on fig 1 and 2 one sees a shift between the true and the asymptotic
Bode plot

_ on fig 3 one sees a strange plot corresponding to the second argument
of frequency bounds.

Do you have any idea ?

Thank in advance.

Emmanuel

//-------------------------------------------------------------------------------------------------------------

//
xdel(winsid());
f1 = 100;
w1 = 2*%pi*f1;
tau1 = 1/w1;
H1 = 10/(1 + tau1*%s); // order 1 system
S1 = syslin('c',H1);
scf(1);
bode(S1);//,[0.001,10000]);
bode_asymp(S1);
xtitle('Order one');
//xs2pdf(1,'order1bode');

m = .125;//sqrt(2)/4;
wn = w1;
H2 = 10/(1 + 2*m*%s/wn + %s^2/wn^2); // order 2 system
S2 = syslin('c',H2);

scf(2);
bode(S2,[.01,1e4]);
bode_asymp(S2);
xtitle('Order two');
//xs2pdf(2,'order2bode');


scf(3);
bode(S1,[0.01,1000]);

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Rafael Guerra Rafael Guerra
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Re: Problems with Bode and Bode asymptotic

Hello,

 

Noting that bode_asymp() takes (rad/s) inputs and that the bracketed syntax [ , ] in Scilab’s help file means optional inputs, please check this:

 

// START OF CODE
xdel(winsid());
fmin = 1e-2;
fmax = 1e4;
wmin = 2*%pi*fmin;
wmax = 2*%pi*fmax;
 
f1 = 100;
w1 = 2*%pi*f1;
tau1 = 1/w1;
H1 = 10/(1 + tau1*%s); // order 1 system
S1 = syslin('c',H1);
scf(1);
bode(S1,fmin,fmax);
bode_asymp(S1,wmin,wmax);
xtitle('Order one');
 
m = .125;//sqrt(2)/4;
wn = w1;
H2 = 10/(1 + 2*m*%s/wn + %s^2/wn^2); // order 2 system
S2 = syslin('c',H2);
scf(2);
bode(S2,fmin,fmax);  // 
bode_asymp(S2,wmin,wmax);
xtitle('Order two');
 
scf(3);
bode(S1,fmin,fmax);
// END OF CODE

 

Regards,

Rafael


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Rafael Guerra Rafael Guerra
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Re: Problems with Bode and Bode asymptotic

You are welcome.

 


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