Problems with linearization (trim and linmod function)

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Soichi 2017-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/322163-problems-with-linearization-trim-and-linmod-function

Hello,

I have a nonlinear simulink system which I would like to linearize. However, no analytical solutions is findable due to non integer exposant a little bit everywhere.

So I tried to linearized it by using the trim function followed by the linmod functions :

[X_trim,U_trim]=trim('model',xss,Iq,2,[],iy); [A,B,C,D]=linmod('model',X_trim,U_trim);

This give results...but when I want to compare both models, the results are not the same !! There is a slight mistake between the models and I would like to mitigate as much as possible this mistake. It's as if the trim point of the nonlinear system are not the same as the trim point of the linear one. I tried to use the trim point to create the Jacobian estimated at trim points but it gives the same mistake.

It drives me crazy. If someone can help, I begging him to help me.

Thanks