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

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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?

Answers (1)

Sainath Varikuti
Sainath Varikuti on 17 Aug 2015
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.
  1 Comment
ml Lin
ml Lin on 18 Aug 2015
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

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