Calculate Time Constant of Discrete or Continuous Transfer Function

Is there a function to provide the value of the time constant of a Continuous or Discrete time transfer function? I mean, I know how to calculate it by hand, but it seems this is so fundamental, I should find a function like tau = TimeConstant(G(s),'step')... Or it should be an output of stepinfo...

Seems such a basic thing in controls, or maybe it's so trivial, no one feels the need for it? Perhaps my google-fu is just really weak tonight?

Thanks for any feedback.

Edit: I should clarify that at this point, I'm just looking at 1st or 2nd order systems.

Answer 1

[Birdman]

Try this function. It takes a first order continuous transfer function as an input and outputs the time constant of it. Hope it helps.

[Russell Senior]

Thanks. That's a good approach. It's still surprising to me that there isn't something built in to matlab. It can do SOO much, this just seems so relatively trivial.

Thanks for the feedback.

[Birdman]

By the way, if this is useful for you, then accept the answer so that other people having the same problem will know that there is a working solution.

[Herdis Hjartar]

Does this function work on 2nd order transfer funktions? It returns one time constant when I try. However, I need two time constants for the 2nd order transfer funktion.

[Russell Senior]

2nd order transfer functions still only have one time constant, but they also have a natural frequency and damping coeffecient.

[Matheus WV]

There was an error in your function: "den" was changed before it was used in the "num" calculation, so "num" would remain the same, as den(len) equals 1.

Here the corrected version.