Proportional control action applied to the flow rate qmi can be used to control the liquid height,

Question:

Proportional control action applied to the flow rate qmi can be used to control the liquid height, as shown in Figure P11.19. Consider the specific plant
Gp (s) = H2(s) / Qmi (s) = 5 (s + 4) / (s + 3) (s + p)
The proportional gain is Kp = 2. The likely value of p is p = 7, but it is known that p might be greater than 7. Use the root locus plot to investigate the roots of the system for p ‰¥ 7.