Hi, guys

I'am very confused with the concept of peaking and overshoot.

Dose they descripe the same thing just in the different domain?

If not, is there any relationship between them?

Thanks a lot~~~

aaron_do wrote on Apr 9^th, 2012, 1:23am:

I know that in a 2nd order system, there is a standard description about Q or damping ratio. How about higher order?

Recently, I have desgned a cascade AMP which is used in the open-loop condition. In the bode diagram, the plot(Mag V.S. Freq) is flat without peaking, while in the trans digram, the overshoot(ring) is series. Do you know how I can solve this problem?

Thank you so much~~~

aaron_do wrote on Apr 9^th, 2012, 1:23am:

Sometime yes and sometimes no.

So - Not necessarily

Peaking can refer to just the spectral response and at a particular frequency

Ringing and damping can refer to either reactive ringing or control systems and their
zeta (phase margin ) response.

(Both have Q, but a feedback system is generally looked at differently than a RL inductive ringing.)

Math types will say that that one is the same, and I will 50% agree with that.

Assuming that, every G(s) has the form of A/(1+sRC), and Gf(s)=B/(1+sRC); So the whole poles,totally 6 with 2 real and 2 pair of compex, is splitting.

You should be able to tell based on the Q of the complex poles.


Aaron

Hi,


Actually I haven't really read up on this in a long time, but just browsing through my book, "Feedback Control of Dynamic Systems", if you have a transfer function which can be written as,

H(s) = (s-a)(s-b)
        -----------
      (s-c)(s-d)(s-e)

you can do a partial fraction expansion to see the effect of each pole. Real poles result in no overshoot, but for complex poles, the amount of overshoot depends on the Q factor, or damping factor of the poles. It seems that you have the transfer function, so you should be able to tell if the overshoot is due to the complex poles just by looking at their Q factor...


regards,
Aaron


BTW, if you are injecting a large signal and looking at the overshoot, then the above explanation doesn't really apply since it is for a linear system.