Hi all, hopefully this is in the correct section here. Any help is really gratefully received. 1. The problem statement, all variables and given/known data I have a coursework, one question asks us to use a 2nd order approximation of the transfer function to..."estimate the settling time (5% of the settling value of output, peak time and rise time (10%-90% of the nalvalue of response) of the closed loop system with 25% of overshoot." Unfortunately the notes given are completely insufficient and provide no examples. 2. Relevant equations G(s) = (2360·K·s + 118000) / ((s + 160)·(s^2 - 1960)) 3. The attempt at a solution My first thought is to simply discard the (s + 160) term, however, this would leave only (s^2 - 1960) as the denominator, and without a middle term, the function has no damping coefficient. Without a damping coefficient the system is undamped, and therefore has no settling time! Now, I realise I can calculate the damping ratio from the overshoot provided, however, this seems like a backward method.