Question

A steady state error will not occur when there is a change to the set value with a control system operating in the mode:
1. Proportional
2. Proportional plus derivative
3. Derivative
4. Proportional plus integral

Answer 1

To answer this , one should know the difference between , Proportional , integral and derivative actions.

PROPORTIONAL : fast time response and minimises output fluctuations. But it cannot elimate offset completely.

INTEGRAL : eliminates offset and returns to steady state.

DERIVATIVE : controls process with rapidly changing output and keeps system at consistent setting.

So a steady state error will not occur if the offset is zero.

It's only possible where integral action is present.  

So the answer is OPTION : 4

PROPORTIONAL PLUS INTEGRAL.