MATLAB: ODE solver for coupled equations

Question

Hi,

I have a set of equations I am trying to solve using an ODE solver. I originally posted on this thinking about using ODE45. After looking into this more, I'm not too sure ODE45 is the best solver since they are highly coupled. I'm now looking at ODE15s. Are there any suggestions? My code is below.

Also, I am getting an error when running my code. I am trying to use dxdt(2) in the equation for dxdt(1) and also use dxdt(1) in the equation for dxdt(2) and dxdt(3). The error is "Undefined function or variable dxdt".

Answer 1

See if this helps:

...
iLoad   = vC/Rload;
dxdt = zeros(7,1);
dxdt(1,:) = (x*(Vs - vC) + y*(-vj1 - dxdt(2) - vC))/L;      % diL/dt  
...