SIMULINK - Solving Differential Equations

Hi,

1. is it possible to solve an IMPLICIT ordinary differential equation ODE in SIMULINK. If yes, do you have an implemented example? Which solvers can be used? If it is possible, is it normal that a message appears saying that an algebraic loop exists? Am I right, that an explicit/implicit solver has nothing to do with an explicit/implicit ODE?

2. is it possible to solve a DAE system in SIMULINK?

Thank you

[Fangjun Jiang]

What is your equation?

[JOKY JOKE]

F(x1, x2, x3, .... xn, y, y') = 0

with x being defined by functions, which partly are also not explicit, for example:

x1 = f(x2, xn)

0 = F(x2, x4, xn)

x3 = f(x2, xn)

...

Answer 1

[Walter Roberson]

I do not know about Simulink directly; you could call a MATLAB function if you needed to. See

<http://www.mathworks.com/support/solutions/en/data/1-15S5M/index.html?product=ML&solution=1-15S5M>

[JOKY JOKE]

Yes, there should be a way in MATLAB. However, I have to implement it in SIMULINK directly. So MATLAB probably won't help.

Answer 2

[Fangjun Jiang]

Since you didn't provide an explicit example, it's hard to say. Maybe this post will give you a little bit of ideas.

http://www.mathworks.com/matlabcentral/answers/18742-how-to-solve-ode-with-simulink

The point is, find all the x', x'', y, y'' etc. in the equation, feed it to an Integrator block, the output will become x, x', y, y' respectively. Use other blocks such as Sum, Product, Gain, Constant to construct the equation. Set up proper initial values for those Integrator blocks. Then you can run simulations to see the dynamic response of every signal.

The solution is only to be numerical.