Consider the open loop transfer function in the feedback loop as shown in Figure 1.
1
G(s) s(s2 + s + 4)
Y(s)
X(s
K
G(s)
Figure 1. Block diagram of a closed loop system with feedback
Using Routh's stability criterion and, determine the range of K for stability. Using direct
substitution method, find the critical period. Assume step change in setpoint X(s)