lsim giving wrong results

When using the transfer function bellow with lsim i get wrong results

3.249e08 s^2

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6.365e07 s^4 + 9.476e07 s^3 + 3.484e08 s^2 + 324615 s + 1596

The first image is what I expected (what I get from teh step functions) and the second one is what I get from lsim.

This is the code I used:

T = 50;
t = linspace(0, T, 1000);
u = ones(size(t));
Gs = tf([0,54150000,17043000,324615,1596],[63650000,94760000,348383000,324615,1596]);
lsim(Gs, u, t);
figure;
step(Gs);

Answer 1

[Ivo Houtzager]

Your end time in seconds do not match between the plots. The lsim simulates only up to 50 seconds which was set by the T variable, while step function simulates up to 12000 seconds (until settled). Set "T = 12000'" instead to match the end time of step function.