P9.21 Consider a unity feedback system with the loop transfer function

(a) Sketch the Bode plot for K = 1. Determine

(b) the gain margin,

(c) the value of K required to pro

vide a gain margin equal to 20 dB, and

(d) the value of

K to yield a steady-state error of 10% of the magni

tude A for the ramp input r t( ) = > At, t 0. Can this gain be utilized and achieve acceptable performance?

K L(s) =G(s)G(s)= s(s+3)(s+5)