How can I create an impulse (delta) signal in Simulink?

How can I create an impulse (delta) signal in Simulink? I looked for it in "Sources" library but there is not.

Answer 1

[Mark Lin]

Hi Alessio,

Use a step response block and linked it to a derivative block can create a delta, impulse, signal.

All you need to do is making sure the response time in your system.

Hope it help.

[Alessio Conte]

Wow thanks, It looks great! I Will try

[Fangjun Jiang]

Alessio Conte, what is your purpose of needing a pulse in Simulink?

The derivative of a step signal is the impulse signal. But that is only theoritical. Doing that in Simulink, the outcome depends on the sample time.

[Jimmy Sølvsteen Nielsen]

I could see several uses for a pulse function in Simulink. For example adding a defined amount of chemical into a mixing tank volume instantaneously, and having delayed mixing in the tank. calculating output concentration is a common chemical enginering task.

I get that takting the derivative of the step function will depend on the sample time, and I wonder why the Dirac function is not available in the Simulink function library?

Answer 2

[Chul-Goo Kang]

Use step input and multiply s in the transfer function of the next block.

[Henry Davies]

Can you please explain what you mean by this?

[SAMSARA NIRVANA]

esta derivando

Answer 3

[Fangjun Jiang]

From the note of impulse():

Note: In discrete time, impulse computes the response to a unit-area pulse of length Ts and height 1/Ts where Ts is the sample time. This pulse approaches the continuous-time Dirac impulse delta(t) as Ts goes to zero.

So you will construct a pulse of width as Ts and height as 1/Ts.

[Alessio Conte]

Hi, thanks for your answer. Not sure to have understood... do you mean that a rectangular signal whose base is Ts and height is 1/Ts is the equivalent of a delta impulse signal? I attach an image of what i mean

[Fangjun Jiang]

That is correct. When Ts->0, the pulse becomes the theoretical delta (the impulse).

Answer 4

[Alessio Conte]

Yes you're right actually...I was just curious of doing what we have seen in classe but actually doesn't make sense.

Thanks!

Answer 5

[Hiromasa]

Thank you for your question.

One way to create an impulse signal is to use Hit Crossing block. (https://www.mathworks.com/help/simulink/slref/hitcrossing.html)

As shown below, Hit Crossing outputs an impulse signal of magnitue 1. The gain block after the Hit Crossing amplifies the signal by the factor of 1/t where t is a discrete time step for the system.

Hope this information helps.