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Scilab Help >> CACSD (Computer Aided Control Systems Design) > Plot and display > bode_asymp


Bode plot asymptote

Calling Sequence

bode_asymp(sl, [wmin, wmax])



syslin list (SISO or SIMO linear system) in continuous time (type state-space or rational).

wmin, wmax

Real scalars: lower and upper frequency bounds (in rad/s).


Plots the asymptote of the system sl.

The optional arguments wmin and wmax (in rad/s) can be used to plot asymptote in a specific range of frequency.

Note that the function bode() or gainplot() must be called before bode_asymp().

Warning: this function is not applicable when the first input argument is a real matrix.


s = poly(0, "s");
h = syslin("c", (s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01));

clf(); bode(h, 0.01, 100); bode_asymp(h);

s = poly(0, "s");
h1 = syslin("c", (s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01));
h2 = syslin("c", (10*(s+3))/(s*(s+2)*(s^2+s+2)));

clf(); bode([h1; h2], 0.01, 100, ["h1"; "h2"]); bode_asymp([h1; h2]);

s = %s;
G = (s+10)/(s*(s+100)); // A rational matrix
sys = syslin("c", G); // A continuous-time linear system in transfer matrix representation.
f_min = .0001; f_max = 1600; // Frequencies in Hz

clf(); bode(sys, f_min, f_max, "rad"); // The optional argument "rad" converts Hz to rad/s
bode_asymp(sys, 10, 1000); // Plots asymptotes in the given range of frequency (in rad/s).

s = poly(0, "s");
h = syslin("c", (s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01));
h = tf2ss(h);

gainplot(h, 0.01, 100, "$\frac{s^2+18 s+100}{s^2+6.06 s+102.1}$"); // Frequencies in Hertz

See Also

  • bode — Bode plot
  • black — Black-Nichols diagram of a linear dynamical system
  • nyquist — nyquist plot
  • gainplot — magnitude plot
  • repfreq — frequency response
  • g_margin — gain margin and associated crossover frequency
  • p_margin — phase margin and associated crossover frequency
  • calfrq — frequency response discretization
  • phasemag — phase and magnitude computation
  • datatips — Tool for placing and editing tips along the plotted curves.
  • show_margins — display gain and phase margin and associated crossover frequencies


5.5.0 bode_asymp() function introduced.
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Last updated:
Thu Oct 02 13:46:49 CEST 2014