How to simplify transfer function？
显示 更早的评论
Hi guys
I have used the function
s=tf('s')
to ceate a transfer function, but I find that Matlab do not simplify the tf at all.
for example.
s=tf('s');
A=1/(1+s);B=A/(1+A);
the result is 1+s/(s^2+3*s+2)
What I want is 1/(2+s)
Anyone know that how to simplify the tf in Matlab?
Thank you!
1 个评论
s=tf('s');
A=1/(1+s); %B=A/(1+A);
B = feedback(A,1)
采纳的回答
Thomas
2012-4-25
Try
s=tf('s');
A=1/(1+s);B=A/(1+A);
minreal(B)
2 个评论
tqy
2012-4-27
Tim
2015-2-5
Looks like a solution to my problem, however I need to find variables from a rewritten tf.
I have a tf G like below
lsys = ss(A B C D); % were all matrices are 3x3
G = tf(lsys);
from which I am intersted in rewriting G(2,2)
G(2,2)=
1.422e-05 s + 4.696e-06
-----------------------
s^2 + 21.76 s + 1.216
into
a * (b*s + 1)
-----------------
(c*s +1)*(d*s+1)
to yield constants a b c d
MatLab does not accept
minreal(G(2,2));
any suggestions?
更多回答（1 个）
Artur Araujo
2016-11-14
1 个投票
You could try H = zpk(G(2,2))
2 个评论
Zuhair Abduljabbar
2021-1-31
Thanks
In addition to this, you can set the DisplayFormat of the zpk model to 'timeconstant' which would show it in the format needed when displayed in the Command Window.
s = tf('s');
G = (1.422e-5*s + 4.696e-6)/(s^2 + 21.76*s + 1.216);
G_zpk = zpk(G);
G_zpk.DisplayFormat = 'timeconstant';
disp(G_zpk);
If you want to store the time constants in variables, you can use zpkdata to first extract the zeros and poles and the compute it using those.
[z,p,k] = zpkdata(G_zpk,'v');
tau_z = -1./z
tau_p = -1./p
Note that for a general approach you will have to account for complex poles and zeros.
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