- C The Open Loop Transfer Function Of A Unity Feedback System Is Given By 350 S 0 2 G S S 4 S D S2 4s 1 (102.08 KiB) Viewed 46 times
(c) The open loop transfer function of a unity feedback system is given by 350 (s - 0.2) G(S) = (s - 4)(s + d)(s2 – 4s + 5)(s2 + 25 - 3) where the constant d is a real number. (i) Find all the poles of the open loop transfer function G(s). (ii) The Nyquist diagrams of G(s) for d = 0.75 and d = 2 are given in Figures 3.2 and 3.3, respectively. For each case, using the Nyquist stability criterion, determine the number of poles of the closed-loop system in the right-half plane. Hence, determine the stability of the closed-loop system when d = 0.75 and d = 2, respectively. [8 marks] Nyquist diagram for d=0.75 3 2 Imaginary Axis -2 -3 -2 -1.5 -0.5 0 -1 Real Axis Figure 3.2 Nyquist diagram for d=2 1 0.5 Imaginary Axis -0.5 -1 -1.6 -1.4 -1.2 -1 -0.4 -0.2 0 -0.8 -0.6 Real Axis Figure 3.3