MATLAB: The system identification models I’ve exported to the work space do not match the results from the toolbox. Why is this happening

Question

I have been using the system identification toolbox to develop two models: a transfer function model and a state space model. Once I developed the toolbox, my goal was to process larger sets of data with a code. However, when I use my code to import the models and plot them, they are different than the results in the identification toolbox. Why is this occurring?

I have attached images of the results, with the code results on the left and the identification results on the right. I have also attached a zip file with the code and the system identification toolbox session.

As a note this has been tried on Matlab versions 2018a, 2017b, and 2017a.

Answer 1

What initial conditions are you using for simulation? Note that by default, the App estimates the initial conditions to maximize the fit to the output signal. See: https://www.mathworks.com/help/ident/ug/estimate-initial-conditions.html