Why everytime I am trying to write the values for num and den in the transfer function block I get num(s)/den(s)?

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?

[Mayra Mita-Gabriel]

You just need to enlarge the transfer function block size by stretching it, because the box is small to show second-order equation in the denominator.

I hope It helps

[ANAND AMAR]

Thanks bro...

[Kurniawan]

i try not working

[Benjamin Thompson]

@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.

Answer 1

[Sam Chak]

Hi @Alexander Guillen & @Kurniawan

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.

Answer 2

[messaoudi]

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')