Bode plot with asymptotes

Bode plot with asymptotes

Description

The function asymp() corresponds to bode(), but it also plots asymptotes for the magnitude and phase graphs. Phase asymptotes are vertical.

asymp() only accepts monovariable transfer functions.

If the transfer function also has a time delay, the time delay is ignored
for the phase asymptotes.

asymp() may be called in two ways only, asymp(h), or asymp(h,wmin,wmax).

• Required Products: Control System Toolbox
• MATLAB release: MATLAB 7.6 (R2008a)

[Jiro Doke]

A similar submission:

http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=2664&objectType=file

I would appreciate a more comprehensive help text at the top. The code is documented pretty well. There are some coding styles that could be better (i.e. the while loops). Since you are plotting the asymptotes, maybe the function could return the break frequencies and the corresponding slopes of the asymptotes. It can have the same behavior as BODE, in which if there are no output arugments, then it would create a plot, and if there are outputs, then it wouldn't create a plot.

[Zain Gurraya]

 

[Anton Cervin]

It does not seem to work.

>> G = (s+1)/(s*(s+10))

Transfer function:
  s + 1
----------
s^2 + 10 s

>> asymp(G)
??? Error using ==> axes
Invalid object handle.

Error in ==> asymp at 120
axes(h);

[Trond Andresen]

I am the author of asymp( ).The problem reported by Anton Cervin has now been fixed. Please tell me if problems still remain.

[Trung Duong]

It's work. Nice job

[Joseph Birbiglia]

Very good, but there are errors with the following transfer function:

G(s) = (s^2+1)/(s*(s^2+4))

---------
??? Error using ==> colon
Maximum variable size allowed by the program is exceeded.

Error in ==> asymp at 147
set(get(gcf, 'CurrentAxes'),'YTick',magmin:ydelta:magmax);
----------------

[John babs]

great stuff. thanks!

[Nabil al-hadawy]

******* Thank you **********
This is function (asymp.m) very nice

[Robert]

i need help...it keeps saying error at asymp at 19

[Bennehar Moussâb]

You're a Geeeeeeeeeeenius
really, great m file
thanx

[Bennehar Moussâb]

 

[Robert Stengel]

It doesn't work with this simple test:
    f11 = -1.2794;
    f12 = -7.9856;
    f22 = -1.2709;
    F = [f11 f12;1 f22];
    G = [-f12;0];
    Hx = [1 0];
    B22 = inv(-Hx*inv(F)*G)
    sys = ss(F, G*B22, Hx,0);
    figure
    step(sys), grid
    figure
    bode(sys),grid
    figure
    asymp(sys)