Once again I want to thank you guys for spending time on this problem. I greatly appreciate your help!
I have attached my Matlab simulink file. It has the plant subsystem and just the single plant transfer function that was obtained by reducing that big plant with multiple block.
I am guess you already know this but incase if you don't - If you double click on that Sub System block it will show the actual plants block diagram with multiple transfer function.
Sorry about not explaing the about the "Big plant". Let me try again.
* If you double click on that subsystem block, there another window will appear where you will be able to see the actual plant. By saying actual plant, its the real plant with multiple blocks.
* since we didnt need to work with the whole plant, we reduced it to the sub system block so that it will only show input, feedback loop and output from the plant.
*Now by using an actual plant (with multiple blocks), we reduced the whole system to 1 single open loop transfer function using block reduction method, which is the one with = 173/(s^2+2.57s) in the transfer block. This is done to make it easier, but basically all system should have Almost same response.
Below I have posted pictures which I had posted couple days ago just to show the actual plant and the subsystem.
Here you can see the Actual plant(with multiple blocks) and Subsystem:
http://img266.imageshack.us/my.php?image=57978335pl0.jpg
And here you can see the same system which was obtained by simplifying block diagram to one single transfer function
http://img388.imageshack.us/my.php?...13240675eo5.jpg
Let me know if I am not explaining well.