Error plotting bode diagram of a transfer function inside a matrix

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Shah Fahad
Shah Fahad 2019-12-9
评论： ahmed solyman 2023-1-11
I am trying to plot bode diagram of an element inside a matrix. The transfer function is alright if i plot G11 which is first row first column matrix. But the bode plot gives error. Is there a different way to plot such bode diagram ? My code is below.
syms s
G11=s-1;G12=s;
G21=-6;G22=s-2;
den=1.25*(s+1).*(s+2);
G=[G11, G12;G21, G22]/den;
G1=G(1,1);
G2=G(1,2);
G3=G(2,1);
G4=G(2,2);
bode(G1)
I even tried G11 by removing all G1...G4. But still doesnt work. Please guide.
  2 个评论
Star Strider
Star Strider 2019-12-9
Shah Fahad’s Answer moved here —
The error is:
Error using bode (line 83)
Not enough input arguments.
ahmed solyman
ahmed solyman 2023-1-11
Regarding MATLAB coding in particular using the bode(sys) code to get the bode diagram. When the numerator equals just a number like (10) without (S), there is an error in computing the bode magnitude because computing it as a 20log(k) “the rule” is not true in MATLAB. Because MATLAB takes into consideration it as log “ln”, not log10.
Please could you tell me how I can solve this issue?

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采纳的回答

Star Strider
Star Strider 2019-12-9
That is not the error.
The error is that you are using the Symbolic Math Toolbox when you need to be using the Control System Toolbox.
Try this:
s = tf('s');
G11=s-1;G12=s;
G21=-6;G22=s-2;
den=1.25*(s+1).*(s+2);
G=[G11, G12;G21, G22]/den;
G1=G(1,1);
G2=G(1,2);
G3=G(2,1);
G4=G(2,2);
bode(G1)

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