Index in position 2 exceed array bound (must not exceed 1)?

A = [ 1 2 -4; 1 1 4; 0 -1 4];
B = [0 ;0; 10];
C = [ 0 0 1];
D = 0;
poles = [ -0.5-1i -0.5+1i -0.7];
Kt = place(A,B,poles);
F = inv(C*inv(-A+(B*Kt))*B);
Acl=A-(B*Kt);
Bcl=B*F;
Ccl=C;
Dcl=0;
syscl=ss(Acl,Bcl,Ccl,Dcl);
t=0:0.1:10;
r=ones(size(t));
x0 = [1 0 0];
[y,t,x]= lsim(syscl,ones(size(t)),t);
figure(1);
plot(t,y,'r');

obpole1 = -0.5+1i;
obpole2 = -0.5-1i;
obpole3 = -0.7;
L = place(A',C', [obpole1 obpole2 obpole3])';
At = [A-B*Kt  B*Kt  ; zeros(size(A)) A-L*C];
Bt = [ B ; zeros(size(B))];
Ct = [ C  zeros(size(C)) ];
obsys = ss(At, Bt, Ct, 0);
x0ob = [0 0 0];
[yob,t,xob] = lsim(obsys,ones(size(t)),t,[x0 x0ob]);
figure(2);
plot(t,yob,'b');

figure(3);
plot(t,yob(:,1),'r');
hold on

plot(t,yob(:,2),'b');

Index in position 2 exceeds array bounds. Index must not exceed 1.

hold on
plot(t,y(:,1),'--r');
hold on
plot(t,y(:,2),'--b')

Answer 1

[Yusuf Suer Erdem]

your 'yob' matrix has a single column but you are asking for its second column. that is why it is happening. recover it please.

Answer 2

[Walter Roberson]

A = [ 1 2 -4; 1 1 4; 0 -1 4];
B = [0 ;0; 10];
C = [ 0 0 1];
D = 0;
poles = [ -0.5-1i -0.5+1i -0.7];
Kt = place(A,B,poles);
F = inv(C*inv(-A+(B*Kt))*B);
Acl=A-(B*Kt);
Bcl=B*F;
Ccl=C;
Dcl=0;
syscl=ss(Acl,Bcl,Ccl,Dcl);
t=0:0.1:10;
r=ones(size(t));
x0 = [1 0 0];
[y,t,x]= lsim(syscl,ones(size(t)),t);
figure(1);
plot(t,y,'r');

obpole1 = -0.5+1i;
obpole2 = -0.5-1i;
obpole3 = -0.7;
L = place(A',C', [obpole1 obpole2 obpole3])';
At = [A-B*Kt  B*Kt  ; zeros(size(A)) A-L*C];
Bt = [ B ; zeros(size(B))];
Ct = [ C  zeros(size(C)) ];
obsys = ss(At, Bt, Ct, 0);
x0ob = [0 0 0];

obsys

obsys =
 
  A = 
           x1      x2      x3      x4      x5      x6
   x1       1       2      -4       0       0       0
   x2       1       1       4       0       0       0
   x3  -6.319  -8.906    -3.7   6.319   7.906     7.7
   x4       0       0       0       1       2   14.92
   x5       0       0       0       1       1   10.35
   x6       0       0       0       0      -1    -3.7
 
  B = 
       u1
   x1   0
   x2   0
   x3  10
   x4   0
   x5   0
   x6   0
 
  C = 
       x1  x2  x3  x4  x5  x6
   y1   0   0   1   0   0   0
 
  D = 
       u1
   y1   0
 
Continuous-time state-space model.

tf(obsys)

ans =
 
        10 s^2 - 20 s - 10
  ------------------------------
  s^3 + 1.7 s^2 + 1.95 s + 0.875
 
Continuous-time transfer function.

[yob,t,xob] = lsim(obsys,ones(size(t)),t,[x0 x0ob]);
figure(2);
plot(t,yob,'b');

size(yob)

ans = 1×2

101 1

figure(3);
plot(t,yob(:,1),'r');
hold on

plot(t,yob(:,2),'b');

Index in position 2 exceeds array bounds. Index must not exceed 1.

hold on
plot(t,y(:,1),'--r');
hold on
plot(t,y(:,2),'--b')

Notice the transfer function equivalent is one input to one output. Notice that your state space C only has one row, and so defines only one output.