Why everytime I am trying to write the values for num and den in the transfer function block I get num(s)/den(s)?
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Why everytime I am trying to write the values for num and den in the transfer function block I get num/den? I see videos online and they just do the same that I do and they get their transfer function on the block.am i missing something?
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Benjamin Thompson
on 20 Jan 2024
@Kurniawan This question is almost four years old. You can write up a new question and attach sample files to help the community understand your problem.
Answers (2)
Sam Chak
on 23 Jan 2024
Let's say we want to input a third-order critically-damped system
into the Transfer Function block. In the field below the Denominator Coefficients, we enter [1 3 3 1] and click 'OK'. Since the polynomial in the denominator is quite long, the block icon will display
as the default. To ensure that the entire transfer function is properly displayed within the block icon, the block needs to be resized. To resize the block systematically, hold down the 'Ctrl' key and drag the corner horizontally until the polynomial is satisfactorily visible.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1597501/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1597506/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1597511/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1597516/image.png)
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messaoudi
on 30 May 2024
t=0:0.1:5;
k=20;
m=5.187;
b=12.223;
wn=sqrt(k/m);
z=b*wn/(2*k);
num=[1/k];
den=[m/k b/k 1];
fct=tf(num,den);
% réponse à une implusion
y1=impulse(fct,t);
figure(1)
plot(t,y1)
title('réponse à une impulsion')
%réponse à un échelon
figure(2)
y2=stepplot(2*fct,t);
title('réponse à échelon')
tau=1/(z*wn);
tr=3*tau;
tm=2.2*tau;
tp=2*pi/(sqrt(1-z^2)*wn);
D=100*exp((-pi*z/(1-z^2)^0.5));
wn=1.965;
den1=[1/wn^2 (2*1)/wn 1];
den2=[1/wn^2 (2*0.4)/wn 1];
den3=[1/wn^2 (2*0.7)/wn 1];
figure(3)
hold on
fct1=tf(num,den1);
y21=stepplot(2*fct1,t);
fct2=tf(num,den2);
y22=stepplot(2*fct2,t);
fct3=tf(num,den3);
y23=stepplot(2*fct3,t);
legend(strcat('z=1'),strcat('z=0.4'),strcat('z=0.7'));
title('reponse a echelon unitaire')
hold off
% reponse rampe
figure (4)
hold on
u=2*t;
y3=lsim(fct,u,t);
plot(t,y3);
plot(t,u);
legend('sortie','entrée')
title('reponse a rampe')
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