delay time - s function

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Kh zaa
Kh zaa 2018-8-26
评论： Aquatris 2018-9-10
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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Aquatris
Aquatris 2018-8-27
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
Kh zaa 2018-9-5
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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Walter Roberson
Walter Roberson 2018-8-27
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
Kh zaa 2018-9-10
kind reminder
Aquatris
Aquatris 2018-9-10
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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