Accessing A and B matrices from discrete state space
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I have written a code to convert continuous time state space models to discrete time using 'tustin' metod. I want to access A and B matrices for each the discretized models. I can access from command window but I want to use them for a later portion of the code. My current code is not giving me10 discretized A and B matrices. Kindly help
clc;
clear all;
A1(:,:,1) =[ 0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 -0.0715];%updated the A matrices, -20 t0 20
A1(:,:,2) =[0 1.0000 0;0 0 1.0000; -0.4875 -0.0383 0];
A1(:,:,3) =[0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 0.0715];
A1(:,:,4) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,5) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,6) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,7) =[0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 0.0715];
A1(:,:,8) =[0 1.0000 0;0 0 1.0000; 0.4875 -0.0383 0];
A1(:,:,9) =[ 0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 -0.0715];
A1(:,:,10)=[0 1.0000 0;0 0 1.0000; 0 -1.3438 -2.5664];
B1=[0;0;1];
C1=[1 0 0];
D1=0;
dt=0.01;
for i=1:10
sys1=ss(A1(:,:,i),B1,C1,D1);
sys2=c2d(sys1,dt,'tustin');
a2(:,:,i)=sys2.a
b2(:,:,i)=sys2.b
end
2 Comments
It seems to do what you want when I run it.
Is there something I am missing here?
clc;
clear all;
A1(:,:,1) =[ 0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 -0.0715];%updated the A matrices, -20 t0 20
A1(:,:,2) =[0 1.0000 0;0 0 1.0000; -0.4875 -0.0383 0];
A1(:,:,3) =[0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 0.0715];
A1(:,:,4) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,5) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,6) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,7) =[0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 0.0715];
A1(:,:,8) =[0 1.0000 0;0 0 1.0000; 0.4875 -0.0383 0];
A1(:,:,9) =[ 0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 -0.0715];
A1(:,:,10)=[0 1.0000 0;0 0 1.0000; 0 -1.3438 -2.5664];
B1=[0;0;1];
C1=[1 0 0];
D1=0;
dt=0.01;
for i=1:10
fprintf('Iteration %2d —————',i)
sys1=ss(A1(:,:,i),B1,C1,D1);
sys2{i}=c2d(sys1,dt,'tustin');
a2(:,:,i)=sys2{i}.a
b2(:,:,i)=sys2{i}.b
end
.
Accepted Answer
Hi SM,
As per my understanding, you have converted ten models from continuous state space to discrete state space using ‘tustin’ and you would like to display the discretized state space matrices ‘a2’ and ‘b2’ for each model simultaneously.
I would suggest you to pre-allocate the discretized state-space matrices 'a2' and 'b2' for faster computation.
You can display 'a2' and 'b2' for each model simultaneously in another 'for' loop using the 'fprintf' and 'disp' functions.
Here is an example showing how you can achieve this:
clc;
clear all;
A1(:,:,1) =[ 0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 -0.0715];%updated the A matrices, -20 t0 20
A1(:,:,2) =[0 1.0000 0;0 0 1.0000; -0.4875 -0.0383 0];
A1(:,:,3) =[0 1.0000 0;0 0 1.0000; -0.4768 -0.0375 0.0715];
A1(:,:,4) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,5) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,6) =[0 1.0000 0;0 0 1.0000;0 -9.8100 0];
A1(:,:,7) =[0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 0.0715];
A1(:,:,8) =[0 1.0000 0;0 0 1.0000; 0.4875 -0.0383 0];
A1(:,:,9) =[ 0 1.0000 0;0 0 1.0000; 0.4768 -0.0375 -0.0715];
A1(:,:,10)=[0 1.0000 0;0 0 1.0000; 0 -1.3438 -2.5664];
B1=[0;0;1];
C1=[1 0 0];
D1=0;
dt=0.01;
% Pre-allocating the discretized state-space matrices
a2 = zeros(3,3,10);
b2 = zeros(3,1,10);
for i=1:10
sys1=ss(A1(:,:,i),B1,C1,D1);
sys2=c2d(sys1,dt,'tustin');
a2(:,:,i)=sys2.a;
b2(:,:,i)=sys2.b;
end
% Display the desired using another 'for' loop
for i = 1:10
fprintf("a2(:,:,%d) = ",i);
disp(a2(:,:,i));
fprintf("b2(:,:,%d) = ",i);
disp(b2(:,:,i));
end
Please refer to the following documentation links to know more about
- 'Pre-allocation': https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html
- 'disp' function: https://in.mathworks.com/help/matlab/ref/disp.html
- 'fprintf' function: https://in.mathworks.com/help/matlab/ref/fprintf.html
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