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Simulink bloc to check if a condition is true during a period of time

Asked by NeedsSupport on 7 May 2013
Hi everyone, I wish to thank you for your time. I need to create a Simulink block: the input of the block is x, the output is outp. the simulation time is 10 steps (the unit I use to express time is the step of the simulation time, not seconds or minutes). The Simulink block does the following: if (x<0.9 during 5 steps of simulation time) then outp=1; Although it looks very easy but I have no idea on how to check the time condition. Any help is welcome. Thank you very much.

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2 Answers

Answer by Babak
on 7 May 2013

You can use a "Weighted Sample Time" block to know what's the sampling time and an "If" block to create a condition.
If you only care about counting the sampling times passed, you can also use a "Counter Free-Running" block that starts counting from 0 as soon as the simulation starts.
When you open the Simulink Library Browser, search for these three blocks' names and use them to make your model.

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in the weighted sample time, you can chose Ts only (or 1/Ts only) and u don't need an input. Output is not dependent on the input because the output is either Ts only (or 1/Ts only). But if you want to add something to Ts or multiply or divide,... you can use other options and it does the operation for you. Ts is the sampling time. I don't thin you need weighted sample time.. a counter works good enough for your case.

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Answer by NeedsSupport on 8 May 2013

Thank you for your help. i just wonder what should be the input for the weighted sample time? a constant (=1) didn't work for me, and the clock didn't work either.

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