Hello everyone,
I am currently working on the identification of the transfer function of my model and I have troubles understanding the systemIdentification Toolbox, let me explain.
The "model output" proposed by the toolbox is what I want. I export the transfer function and use lsim to plot it on my command window but I get something else.
I assume that the function compare is what the toolbox uses to plot the function (because the plot is very similar and there is a goodness of fit coefficient) but I don't know why this type of plotting is different from the lsim type.
I'm using the same input/output data, the same transfer function, the same sample time and yet both plots are different. Here's a picture to show you :
and the code used to plot the figure:
test1 = iddata(Y5,U5,0.01); %iddata(output,input,Ts)
sys5 = tfest(test1,4,0); %tfest(model,pole,zero)
test2 = lsim(sys5,U5,T5);figurecompare(test1,sys5)hold onplot(T5,test2,'r')title({'Difference between "compare" function and "lsim" function' 'TF : 4 poles 0 zero'})legend('Output measured','"Compare" function','"lsim" function')
Does someone know how both functions work ? Or why they are different?
It would help me a lot, thank you in advance!
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