Lsim function returns an array filled with Nan
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Im using lsim to simulate a MVE, for some reason the response y2 is filled with NaN when It should have the system response.
R=1;
C1=1*10^-6;
L=1*10^-3;
A= [1/C1 -1/C1 0; -2*(R/L) R/L -1/L; R/L (-5/2)*(1/L) 1/L];
B= [0 0; 1/L 0; 0 -1/(2*L)];
C= [0 1/2 0; 0 0 1];
D= [0 1/(2*R); 0 0];
sys = ss(A,B,C,D);
t2 = 0:0.01:20;
u1 = 5*heaviside(t2-3);
u2 = 10*heaviside(t2-6);
u = [u1(:), u2(:)];
[y2,t2]=lsim(sys,u,t2);
y2
回答（1 个）
Hi Gabriel,
Recheck the model. As written it has two unstable poles way out in the right half plane. That will be very difficult to simulate.
R=1;
C1=1*10^-6;
L=1*10^-3;
A= [1/C1 -1/C1 0; -2*(R/L) R/L -1/L; R/L (-5/2)*(1/L) 1/L];
B= [0 0; 1/L 0; 0 -1/(2*L)];
C= [0 1/2 0; 0 0 1];
D= [0 1/(2*R); 0 0];
sys = ss(A,B,C,D);
format short e
eig(sys)
heaviside(0)
You can change that 1 using sympref, which is probably what you want. Or define a new function like
unitstep = @(t) 0.5*(t==0) + heaviside(t);
unitstep(0)
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