frequency relay function for Zeigler nichols 2?

Hi,

I have to write matlab code/function for Zeigler Nichols 2(Closed Loop).

I wrote the code for solve of pid parameters, but I have problems in simulation of Closed Loop.

I understand that I need of relay, but as function or command I could not found.

 ----r-->+---e-|relay|--|PID|--u-|PLANT|-----------y->
         ^-                                 |
         |__________________________________|

[Azzi Abdelmalek]

What is a relay?

Answer 1

[Azzi Abdelmalek]

Maybe you mean a delay block

Answer 2

[Myumyun]

relay info I'm sorry http://www.mathworks.com/help/simulink/slref/relay.html

Answer 3

[Myumyun]

If there isn't function/command for this,

Pls you give me some information on how I can write code.