system identification using closed loop data

hello..can i ask a question? this is for my final project..i need to model system using system identification. but my data in closed loop system.. i try many thing but at the end my result for validation to poor. can u help me

[Arkadiy Turevskiy]

you need to provide specific information about what you have tried and what does not work if you want help.

[nurul]

i have try to do direct system identification, but I need to validate using same data I use in this project. i get the best fit by using direct process is too small.