MATLAB Answers


Negative Values in Step Response

Asked by Kenneth
on 26 May 2013

Hi guys,

I just noticed something interesting on MATLAB.

I was working with a transfer function, and I inserted a delay using a Pade approximation, and plotted the step response. At first glance, it seems just like any other step response, however when i zoomed in on the origin, I noticed that it slightly dips into negative values before coming up.

I've never noticed this before. Anyone have any idea why it does this?


1 Answer

Answer by Azzi Abdelmalek
on 26 May 2013
 Accepted answer

This is normal, when your transfer function contains positives zeros

example H(p)=(-p+2)/(p^2+2p+1)

step([-1 2],[1 2 1])


on 26 May 2013

Hmm indeed it did have a positive zero. Why does it do this though? What does it mean?

on 26 May 2013

Interesting stuff, thanks for the info!

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