How to use Simulink System Identification with Arbitrary I/O Data?

I'm trying to develop a system model of my physical plant using the Simulink PID tuner.

I'm following this guide: https://au.mathworks.com/help/control/getstart/interactively-estimate-plant-parameters-from-response-data.html

I'm not 100% sure on what the input/output data should be however. I'm currently unable to generate a step response for the system for the input/outputs.

The system currently has a pretty good PID controller implemented in it. When I record the I/O data does it matter that the system is already 'controlled'?

How should I collect my data for system identification to develop a better PID tune?

Answer 1

[Arkadiy Turevskiy]

Are you trying to improve your PID? The IO data to collect should be the data from the plant, i,e, input to the plant and output from the plant. In the page you linked to, there is clear notation where you need to collect IO data.