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.

Gls) Rx) His) FIGURE AP2.3 input. Feedback system with a disturbance