It seems that you are trying to solve a matrix differential equation. If you are using ode45, one possible way this error can occur if you call it like this
ode45(@(t,x) OD, [0 10], [1; -1; 0; 0])
The correct syntax is
ode45(@(t,x) OD(t,x), [0 10], [1; -1; 0; 0])
ode45(@OD, [0 10], [1; -1; 0; 0])
The following shows working code with random values for matrices
global A B C Da K
A = rand(4);
B = rand(4);
C = rand(4);
Da = rand(4);
K = rand(4);
ode45(@(t,x) OD, [0 10], [1; -1; 0; 0])
function xdot = OD(t,x)
global A B C Da K
Aa=A+(B*K*C);
Ba=B*Da;
u=K*x;
xdot=(Aa*x)+(Ba*u);
end
Also, using global variables is not a good coding practice. Following shows how to pass these matrices to function OD without using global
A = rand(4);
B = rand(4);
C = rand(4);
Da = rand(4);
K = rand(4);
ode45(@(t,x) OD(t,x,A,B,C,Da,K), [0 10], [1; -1; 0; 0])
function xdot = OD(t,x,A,B,C,Da,K)
Aa=A+(B*K*C);
Ba=B*Da;
u=K*x;
xdot=(Aa*x)+(Ba*u);
end
Best Answer