My code won't run, error message :Unrecognized function or variable 'ss'. Error in Q4_109 (line 19) Sys=ss(A,B,C,D);

clear;clc
close all
M=[4 0 0 0;0 3 0 0;0 0 2.5 0;0 0 0 6];
C=[4 -1 0 0 ;-1 2 -1 0;0 -1 2 -1;0 0 -1 1];
K=[500 -100 0 0;-100 200 -100 0;0 -100 200 -100;0 0 -100 100];
x0=[0;0;0;0.01];
v0=[1;0;0;0];
B=[0;0;0;0;0;0;0;1];
t=0:0.01:80;
u=sin(4*t);
A=[zeros(4,4) eye(4);-inv(M)*K -inv(M)*C];
X0=[x0;v0];
C=[eye(4) zeros(4,4)];D=[0;0;0;0];
Sys=ss(A,B,C,D);
[x,tout,X]=lsim(Sys,u,t,X0);
plot(tout,x(:,1),tout,x(:,2),tout,x(:,3),tout,x(:,4))
xlabel('Time');ylabel('x')
legend('x_1','x_2','x_3','x_4')

I'm trying to code and plot this... (see attached)

Answer 1

[Star Strider]

If you are getting an error that MATLAB cannot find the ss function, then you need to license and install the Control System Toolbox.

The code otherwise works as written —

M=[4 0 0 0;0 3 0 0;0 0 2.5 0;0 0 0 6];
C=[4 -1 0 0 ;-1 2 -1 0;0 -1 2 -1;0 0 -1 1];
K=[500 -100 0 0;-100 200 -100 0;0 -100 200 -100;0 0 -100 100];
x0=[0;0;0;0.01];
v0=[1;0;0;0];
B=[0;0;0;0;0;0;0;1];
t=0:0.01:80;
u=sin(4*t);
A=[zeros(4,4) eye(4);-inv(M)*K -inv(M)*C];
X0=[x0;v0];
C=[eye(4) zeros(4,4)];D=[0;0;0;0];
Sys=ss(A,B,C,D);
[x,tout,X]=lsim(Sys,u,t,X0);
plot(tout,x(:,1),tout,x(:,2),tout,x(:,3),tout,x(:,4))
xlabel('Time');ylabel('x')
legend('x_1','x_2','x_3','x_4')

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[Abuqasem]

you're awesome thank you!

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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Answer 2

[the cyclist]

As you can see, I was able to run your code here.

I expect you do not have the ss function, which is in the Control System Toolbox. You need to have that toolbox installed.

[Abuqasem]

I appreciate your response thank you!