2. (40 pts) The open loop transfer function of a unity feedback control system is given as
s(s2+4)
a) (12 pts) Draw the root locus of the system for K > 0, indicating all particulars such as asymptotes
and their centroid, angles of arrival or departure, crossing points, break in/away points, etc.
Draw the root locus neatly; neatness will be graded.
b) (3 pts) Determine the range of positive K values for which the system is stable
(c) (5 pts) In one sentence, explain why using a single PI controller will not make this system stable
(d) (10 pts) Suppose you use a PD controller Gc(s) = Ka(s + 8). Determine the range of Ka values
for which the system is stable.
(e) (10 pts) Let Ge(s) = Ka(s - z). Determine the range of z for which the system can be stabilized
for all Ka values. Explain your work in detail.