Fall 2001 16.313-3 Use logarithmic since if (s+1)(s+2) pg s+3)(s+4 log s+1|+log s+2-log s+3-log s+4 and each of these factors can be calculated separately and then added to get the total FRF Can also split the phase plot since (s+1)(s+2) arg (s+3)(s+4) arg(s +1)+arg(s+ 2) arg(s +3)-arg(s+4) The keypoint in the sketching of the plots is that good straightline approximations exist and can be used to obtain a good prediction of the system responseFall 2001 16.31 3–3 • Use logarithmic since if log |G(s)| =






(s + 1)(s + 2) (s + 3)(s + 4)






= log |s + 1| + log |s + 2| − log |s + 3| − log |s + 4| and each of these factors can be calculated separately and then added to get the total FRF. • Can also split the phase plot since arg (s + 1)(s + 2) (s + 3)(s + 4) = arg(s + 1) + arg(s + 2) − arg(s + 3) − arg(s + 4) • The keypoint in the sketching of the plots is that good straightline approximations exist and can be used to obtain a good prediction of the system response