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Kh zaa
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delay time - s function

Asked by Kh zaa
on 26 Aug 2018
Latest activity Commented on by Aquatris
on 10 Sep 2018
hello sir, i use level 1 S-Function in my simulink model. I need s function to wait for 2 sec, then collects the measurements. How i can do that ?

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Kh zaa
on 26 Aug 2018
measurements from simulink are collected and, then, entered to S Function as input. S- function performs an controller. but i need s function to wait 2 second to avoid the transient values of measurements and then perform the controller.
Aquatris
on 27 Aug 2018
You can use a switch block. The two inputs to the switch can be "constant 0" and the actual signal. Then you will attach "clock" block to the decider and set the switch block to give constant 0 as output if t < 2 and actual signal if t > 2.
Kh zaa
on 5 Sep 2018
dear Aquatris, my model is very complex with more than 350 measurements. i need to make delay inside S function. thanks

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1 Answer

Walter Roberson
Answer by Walter Roberson
on 27 Aug 2018

Aquatris's solution is the correct one in many cases.
However, if you are feeding into a controller, then the controller might be taking the differentiation, and the sharp change between 0 and non-zero would be a problem for differentiation. Therefore for you situation you should probably instead use an enabled subsystem https://www.mathworks.com/help/simulink/ug/enabled-subsystems.html, in which the control signal is the output of a comparison block between the clock and a constant block which is the enable time.

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Kh zaa
on 6 Sep 2018
My model as follows: S- function collects measurements from Simulink and, then, execute its code. the outputs of S -function are used to update parameters in SIMULINK. the process is repeated until the simultaion is stopped. my problem is that I need S -function to wait for 2 seconds after running the model and, then, execute its code. In other words, i do not need the values of the meaurements during the first 2 seconds of simulation time. Another thing, after updating the parameters (from s-functions output), I need s -fuction to wait also 2 seconds. Thanks in advance
Kh zaa
on 10 Sep 2018
kind reminder
Aquatris
on 10 Sep 2018
You can also use a "rate transition" block, which samples the signal in a different time than the simulation time. See image below where I use a sine wave as the source signal and the rate transition block allows to sample it every 2 sec (Zero order hold) and ignores the changes if 2 sec had not passed. Is this what you are trying to achieve?

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