Question

Assertion (A): A PI controller increases the order of the system by units but decreases the steady state error.

Reason (R): A PI controller introduces a pole at either the origin or at a desired points on the negative real axis.

(a) Both assertion and reason are true and R is correct explanation of A

(b) Both A and R true but R is not correct explanation of A

(c) A is true but R is false

(d) A is False but R is true

The question was posed to me during an interview.

My question is based upon Effect of Adding a Zero to a System in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems

Answer 1

Right choice is (a) Both assertion and reason are true and R is correct explanation of A

Explanation: I is proportional +integral controller. Thus integral controller add a pole either at origin or at the desired point on the negative real axis, so order of the system gets increased but it reduces the steady state error of the offset error.