Hi
I assume the signal shown in the image is the input signal. I think whatever you are doing is correct, you might be getting same curve with slight shift of 1 time unit with same magnitude. It may be because of the transfer function you have selected as its coefficients are very small. Try with different transfer function like
tau=10;
Tf=100;
sys = tf(1,[1,10]);
[u0,t] = gensig("square",tau,Tf);
u = 2*u0-1;
lsim(sys,u,t)
You will see a significant change in response. Hope it will help!
