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MathGroup Archive 2005

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Re: Re: Re: bode diagram

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57075] Re: [mg57040] Re: [mg57016] Re: [mg56979] bode diagram
  • From: DrBob <drbob at bigfoot.com>
  • Date: Sat, 14 May 2005 04:58:14 -0400 (EDT)
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

I used the code below for each example at the link:

http://www.swarthmore.edu/NatSci/echeeve1/Ref/Bode/BodeRules.html#Examples

In several cases I got what appears to be the same result as pictured at the link, but in other cases I got very different plots. The fourth example is particularly strange. Am I doing this wrong?

I'm plotting magnitude and phase on a single plot in each case, and I'm ONLY plotting the exact curves -- assuming I have the right formulae for them. I see no point in approximate plotting techniques, with exact plots readily available.

Needs["Graphics`Graphics`"]
SetOptions[LogLinearPlot, PlotStyle ->
     {Red, Blue}, PlotRange -> All,
    ImageSize -> 500];
db = 20*Log[10, Abs[#1]] & ;

Clear[h]
h[s_] = 100/(s + 20);
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 1, 10^3}];

h[s_] = (100*s + 100)/(s^2 + 110*s + 1000);
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 10^(-2), 10^4}];

h[s_] = 10*((s + 10)/(s^2 + 3*s));
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 10^(-1), 10^3}];

h[s_] = (-100*s)/(s^3 + 12*s^2 + 21*s + 10);
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 10^(-2), 10^3}];

h[s_] = 30*((s + 10)/(s^2 + 3*s + 50));
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 10^(-1), 10^3}];

h[s_] = 4*((s^2 + s + 25)/(s^3 + 100*s^2));
LogLinearPlot[{db[h[s]], Arg[h[I*s]]*(180/Pi)},
    {s, 10^(-1), 10^3}];

Bobby

From: Pratik Desai <pdesai1 at umbc.edu>
To: mathgroup at smc.vnet.net
References: <200505120633.CAA08967 at smc.vnet.net>

David Park wrote:

> I'm fairly certain it could be done with Mathematica if you would only tell
> us what a bode diagram is and give us some sample data of function that you
> want to plot in the diagram.
>
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
>
> From: GaLoIs [mailto:lanellomancante at inwind.it]
To: mathgroup at smc.vnet.net
>
>
> hi, like plotting simple bode diagrams of systems. could you give me some
> information about it? i can do it with another program, but i'd like to see
> how mathematica works
> thank you
>
>
>
>
>
>
>
Here is a nice example from a website I found.

*http://www.swarthmore.edu/NatSci/echeeve1/Ref/Bode/Bode.html*


-- 
DrBob at bigfoot.com


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