How to put a variable in transfer function num and den?

when i include a symbolic variable in a numenator of transfer function

clear all;clc;

syms k;

n1=[k]; d1=[1 10]; G=tf(n1,d1);

I get this==> The values of the "num" and "den" properties must be row vectors

or cell arrays of row vectors, where each vector is nonempty and

containing numeric data. Type "help tf.num" or "help tf.den" for

more information.

Answer 1

[Star Strider]

You are mixing Control System Toolbox and Symbolic Math Toolbox funcitons and syntax.

You cannot do that!

Try this instead:

n1=@(k)k;    
d1=[1 10];    
G=@(k)tf(n1(k),d1);

Note that it will be necessary to supply a numeric value for ‘k’ to use this, for example:

figure
bode(G(5))

.

[Mohammad Alzoubi]

I can not run this code and include k in The tf?

clear;clc; syms s t k;

%the TF=k/(s^2+4*s+3+k) R=1/s; num=@(k) [k]; den=@(k)[1 4 3+k]; TF=tf(num,den); ys=TF*R; sys=s*ys; yss=limit(sys,s,0); E=R-TF; sE=s*E; ess=limit(sE,s,0); yt=ilaplace(ys);

[Star Strider]

Do not use the Symbolic Math Toolbox for this.

Use the Control System Toolbox, and it will work correctly.