Reducing fast dynamic poles in a transfer function.

Imagine I have a tf that looks something like this: G(s) = 1/((s+70)*(s+5))

Is there some sort of command that can return a transfer fucntion that get's rid of the fastest dynamic pole?

In the example given above my output would be something like this: G(s)=1/(s+5).

Thanks in advance.

Answer 1

[Paul]

Maybe freqsep() is what you want:

>> G=tf(1,conv([1 5],[1 70]))

G =
 
         1
  ----------------
  s^2 + 75 s + 350
 
Continuous-time transfer function.

>> [Gs,Gf]=freqsep(G,10)

Gs =
 
  0.01538
  -------
   s + 5
 
Continuous-time transfer function.


Gf =
 
  -0.01538
  --------
   s + 70
 
Continuous-time transfer function.

>> bode(Gs,h);

The dc gain of Gs will need to be adjusted to match the dc gain of G if you intend to use Gs as a low frequency approximation to G. This doc page is a good source for starters. There are also additional pages in Robust Control Toolbox for model reduction.

[Edward Simpson Songel]

Hello Paul.

This command is exactly what I was looking for, managed to do what I needed.

Thanks for the quick reply!

I will be fowarding this post to my class-mates if that's alright.

Kind regards.

Edward

[Edward Simpson Songel]

P.S. Thanks for the further resources on the subject too.