P9.28 Consider the feedback system shown in Figure P9.28.

(a) Determine the value of Kp so that the phase margin is P.M. = 60.

(b) Using the P.M. obtained to predict the percentage overshoot of the closed-loop system to a unit step input.

(c) Plot the step response and compare the actual percent overshoot with the predicted percent overshoot.

FIGURE P9.28 A unity feedback system with a proportional controller in the loop. Controller Process Ea(s) R(s) Kp Y(s) s(s+2)