Consider the feedback control system in Figure AP2.3. Define the tracking error as E(s) = R(s)−Y(s).

(a) Determine a suitable H(s) such that the tracking error is zero for any input R(s) in the absence of a disturbance input (that is, when Td (s) = 0).

(b) Using H(s) determined in part (a), determine the response Y(s) for a disturbance Td (s) when the input R(s) = 0.

(c) Is it possible to obtain Y(s) = 0 for an arbitrary disturbance Td (s) when Gd (s) ≠ 0? Explain your answer.