Question

The following controller has the maximum offset

• A. P-I-D controller
• B. P-D controller
• C. P-I controller
• D. P-controller

Hint:

Proportional controller has steady-state offset. Integral action is required to eliminate offset.

Answer 1

The Correct Option is D

Offset means the steady-state error remaining after a control action. A proportional controller gives output proportional to error. For a proportional controller: \[ m=K_c e \] where, \[ K_c=\text{controller gain} \] and \[ e=\text{error} \] In proportional control, some error must remain to produce the required controller output. Therefore, proportional controller has offset. Integral action eliminates offset because it continues to act as long as error exists. So P-I and P-I-D controllers can remove steady-state offset. Derivative action improves response but does not remove offset by itself. Among the given controllers, P-controller has maximum offset. Therefore, the correct answer is: \[ \text{P-controller} \]