PID: why there is no oscillation on my results

Hi all, In my simulink file, there is PID controller and s-function block diagram.Refer below

<<http://s1009.photobucket.com/albums/af218/syarinazulkifeli/?action=view&current=diagram.jpg>>

My manipulated variable is heat, control variable is reactor temperature. so, my result of reactor temperature without controller is as below:

<<http://s1009.photobucket.com/albums/af218/syarinazulkifeli/?action=view&current=reactorT.jpg>>

However, after put in proportional parameter until 2.3e4, there is no oscillation on my reactor temperature result, only got this result,

<<http://s1009.photobucket.com/albums/af218/syarinazulkifeli/?action=view&current=result.jpg>>

i changed a lot of numbers for proportional parameter but still no oscillation appear.if the maximum number,only straight line result comes out.i do not know what should i do.I hope somebody can help me... Thank You

[Arkadiy Turevskiy]

your images do not display, so hard to help you without seeing the model

[yana osman]

i'm sorry.i do not know how to attach the pictures. or else you can go thru the above link.hope this will not troubling and really hope that you can help me. thank you in advance

Answer 1

[K E]

Is it possible that your time step is too large to resolve the oscillations? If so this blog will be helpful.