Disturbance Responce for a simple control system

[Hiroshi Shinozawa]

I think about the following Feedback Loop

DISTURBANCE -----------------------
                                   | 
STEP INPUT --->O---->|Controller|--O--|Process|--O---> OUTPUT
               |                                 |
               -----------------------------------
I know Step Input Responce is easily calculated by OCST 
"step" function.
But I don't know how to calculate the Step Disturbance
Responce.

I use "lsode" function to simulate a step disturbance
responce as well as a step input reponce.
I am searching a simple function like OCST "step" to 
simulate step disturbance respponce.
Advise me please. 
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address@hidden
Hiroshi_Shinozawa
YHC TC Phone 731-22535
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