Problem 2: (25 pts)
Suppose the open-loop unstable plant, P(s) = (s+1)/(s^2-9), and the controller C(s) = k(s + 2) are structured in a unity feedback control scheme.
(a) Find the closed-loop transfer function from r to y as a ratio of polynomials in s:
G(s) = Y(s)/R(s) = (b_ms^m + b_{m-1}s^{m-1} + ... + b_1s + b_0) / (a_ns^n + a_{n-1}s^{n-1} + ... + a_1s + a_0)
(b) Find the range of k such that the closed-loop system G(s) is stable.
(c) Regarding the steady-state error for tracking, what is the System TYPE?
(d) Assume k = 5. Can this system track a step input perfectly? If so, prove it mathematically. If not, determine the steady-state error e(infinity) when the reference r(t) is a unit step function.
(e) Suppose the above controller is replaced by a controller of the form:
C1(s) = k/s
Determine whether a controller of this form can produce a closed-loop system capable of tracking a step reference with zero steady-state-error e(infinity)_step = 0.