How do I find out the ODE function that the solver in Simulink uses?

I would like to find out the ODE function that the "ode45 (Dormand-Prince)" solver in Simulink uses. When I call the MATLAB function "ode45", the input argument requests for a ODE function that describes the system.

However in Simulink, it doesn't tell me the ODE function it uses. Is there any way to find out?

Answer 1

[Sainath Varikuti]

Hi Lin,

In Simulink a dynamic system is represented as states. Therefore, it is not possible to get the mathematical representation of ODE function directly. However, you can obtain the state-space representation of Simulink model using Simulink Control Design as discussed here . The state-space object will give us the system dynamics.

Regards,

Sainath.

[ml Lin]

Hi Sainath,

Thanks for the reply. I see. But how does Simulink compute the states during every iteration without knowing the mathematical representation of the ODE?

What I don't understand is that, for Simulink to obtain the state space representation, wouldn't it need to know the system dynamics first?

Or is there some technique involve that I am not aware of?

Regards, Lin