Reducing state space order by doing matrix operations

Dear All

I have (11 by 11) state matrix, three inputs and 9 outputs in the attached MATLAB file. I want to drop the second plant input , first four outputs, output number 6, 7 and 8 , as I dont need these for further operations by using a controller just like an attached example. can anyone please help me in this regard?

A1 = [-0.2506     1.989;    -0.08803       -1.167];
B1 = [0    1  0.3;1    0    0];
C1 = [1    0; 0      1];
D1 = [0    0    0;0    0    0];
sys = ss(A1,B1,C1,D1)

If I drop the first input and second output , then use the following command

sys = sys(1,2:3);

This will reduce the size of input and output operations. Similar help is needed for the attached

% code
A = [0         0    0.2616         0         0         0         0         0         0    0.7483   -0.6634;...
   0         0   -0.2616         0         0         0         0         0         0    0.6634    0.7483;...
   0         0         0         1         0         0         0         0         0         0         0;...
   0         0    -8.205    0.1144    -141.7     125.6         0         0   -0.2498    -4.593    -90.72;...
   0         0         0         0         0         0         1         0         0         0         0;...
   0         0         0         0         0         0         0         1         0         0         0;...
   0         0         0         0         0         0         0         0         0         0         0;...
   0         0         0         0         0         0         0         0         0         0         0;...
   0         0         0         0         0         0         0         0         0         0         0;...
   0         0   -0.1448  -0.04184    0.8347   -0.7405         0         0    0.4732   -0.9367     1.141;...
   0         0     0.078    0.1954   -0.2402    0.2131         0         0    0.2852   -0.2871    -4.836]

B = [0          0          0;...
     0          0          0;...
     0          0          0;...
    -0.6585     0.3862     0;...
     0          0          0;...
     0          0          0;...
     1          0          0;...
     0          1          0;...
     0          0          1;...
   -0.1434  -0.002274      0;...
  -0.001117  -0.07752      0]

C = [ 1    0    0    0    0    0    0    0    0    0    0;...
    0    1    0    0    0    0    0    0    0    0    0;...
    0    0    1    0    0    0    0    0    0    0    0;...
    0    0    0    1    0    0    0    0    0    0    0;...
    0    0    0    0    1    0    0    0    0    0    0;...
    0    0    0    0    0    1    0    0    0    0    0;...
    0    0    0    0    0    0    1    0    0    0    0;...
    0    0    0    0    0    0    0    1    0    0    0;...
   0    0    0    0    0    0    0    0    1    0    0]

D = [ 0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0;...
      0   0   0];

Thank you

Answer 1

[Barkat]

Can I do it like the following as well? B=[B(:,1) B(:,3)]; C=[C(1,:);C(2,:);C(7,:);C(11,:)];

[Aquatris]

Yes, and you need to adjust the D matrix as well. Your D matrix is all zeroes so Matlab also accepts if you do

 D = 0;

Answer 2

[Aquatris]

Removing 2nd plant input;

B(:,2) = [];

Removing the outputs 1,2,3,4,6,7,8;

C([1 2 3 4 6 7 8],:) = [];.

Adjusting the D matrix;

D(:,2) = [];
D([1 2 3 4 6 7 8],:) = [];

[Aquatris]

Alternatively, you can use feedback function and define the indices where you want your controller and system to connect without removing any input or output from your system;

sys = feedback(sys1,sys2,feedin,feedout)