Assertion (A): The closed-loop pole-zero dipole introduced by the PI controller does not contribute significantly to the transient response of the closed-loop system.

Reason (R): The PI controller adds a pole at s = 0 and a zero at s = −z to the closed-loop transfer function.

• Increasing the type number of the system drastically improves its steady-state response.
• If an integral controller is added to a closed-loop system, the type number increases, but its transient response deteriorates or the system becomes unstable.
• If a proportional control term is added to an integral term, the controller has a pole and a zero.
• The transfer function of the PI controller is. 

          \(C\left( S \right) = {K_p} + \frac{{{K_I}}}{S}\)

          \(\Rightarrow {K_P}\frac{{s + a}}{s}\)

          \(a = \frac{{{K_I}}}{{{K_p}}}\)

By placing the controller zero close to the pole at the origin, the controllers pole-zero almost cancels, having a negligible effect on transient response. Hence Assertion (A) is true.

⇒ The PI controller adds poles and zero’s, near the origin. So the Reason (R) is false.

∴ (A) is true, but (R) is false.