A root locus of the feedback system is shown in Figure 5-7 for varying k k, with the ratio fixed at 4. A value of z = 0.5 was assumed for the ki system lag. Values of k, varying from 0 to 0.75 were used. It can be seen from Figure 5-7 that the closed system is stable for all non-zero k, . There is one closed-loop real pole and a pair of complex conjugate poles. For a value of k, = 0.75, the complex poles have a damping ratio of 0.87. If the value of k, is increased further beyond 0.75, the damping ratio of the complex poles decreases and the system becomes less damped