Modifying state in S-function

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Thiago Marinho 2011-7-12

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Hello guys,

I am working with Level- 2 M files S-functions and I have a problem trying to modify the state.

As in a switching controller ( state jumps) I want to assign manually the value of the state after a certain condition.

So I tried to do something like

block.ContStates.Data = mynewthing;

but it looks like this is completely ignored by the simulation. I have know idea of making it work.

I have seen a class called SimState and function a function called SetSimState in the s-function template but I don't know how to use it and I am having trouble finding documentation on it.

Does someone know how to do this?

Thanks!

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Answer 1

Titus Edelhofer 2011-7-13

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Hi Thiago,

you cannot directly set the continues states, they are computed by numerical integration. You can only compute the derivative (see function Derivatives in MATLAB\toolbox\simulink\blocks\msfuntmpl.m). If you would have discrete continuous states, then take a look at the function Update, where you set the discrete state (DWork) to whatever you want ...

Titus

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Thiago Marinho 2011-7-19

Hi Titus,

Thank you for your answer.

If you cannot directly set the states, how can one deal with state switching systems in continuous time ?

Thiago

Titus Edelhofer 2011-7-25

It depends on what is "continuous" for you: a continuous state is the x in some differential equation like x' = 2*x. This state does not switch (only the differential equation might switch, but this can be done). If you have something like x = g(x, y), where y is the input and x is the x of the timepoint before, you can do this (see my answer above). Simulink can model both in one system ...

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