The transfer function of an open loop system is:
G0(s) = 52 + 2s + 4
The open loop system consists of a controller, differentiator, and plant whose transfer functions are Gc(s), Ga(s), and Gp(s) respectively. All three components are connected in series.
Determine the steady-state error of the closed-loop system if the input is (i) a unit step function or (ii) a unit ramp function of magnitude 10. Assume H(s) = 1. (2 marks)
Sketch the root locus of the closed-loop system for K > 0, indicating clearly the starting and ending points (if any), asymptotes (if any), intersections between the root locus and the imaginary axis (if any), break-away and break-in points (if any), as well as the departure angles from the open-loop poles (if any). (6 marks)
Comment on the types of stability of the closed-loop system that are achieved for different positive values of K. Make reference to the values of the damping ratio. (3 marks)
What are the values of the poles and K if the system is critically stable? (1 mark)
What values of K would ensure ζ = -0.707? What would be the values of the poles in this case? (2 marks)
Figure 1