Help Using Simulink tp draw ODE

Hi,

I was wondering if someone could help me create a basic differential equation in Simulink. I'm trying to create the following equations

I tried using this as an example ODE to help me solve this problem but it doesn't seem to help. The link above has a very similar ODE. When I create two of what is done in the example and try and connect it to a XY Graph I don't get anything so I'm doing something wrong but am not sure what. Thanks for any help.

[Mischa Kim]

Please add follow-up questions as comments to the respective answer.

Answer 1

[Mischa Kim]

Dylan, the basic structure looks like this:

Try using an embedded MATLAB function to compute the state derivative

function Xdot = fcn(X, u)
  Xdot = [0; 0];
  x    = X(1);
  y    = X(2);
  Xdot = [y*u; -x*u];
end

As a final note, make sure to adjust the limits in the XY Graph according to the signal outputs.

[Mischa Kim]

Double-click the integrator block and add the intial conditions, e.g., [1; 1] ;

Answer 2

[Dylan]

Hey,

I seem to be having some issues. I created the circuit like you did,

and used the following function

But when I run it I don't get anything on the graph

Am I doing something wrong? Also how would I go about entering in initial conditions for X and Y if they were given. Thanks for your help.

[Mischa Kim]

Dylan, could you please post follow-up questions as comments? Did you get it to work with setting the initial conditions? See comment on top.