Question

A unit integrator is applied to a modified system along with a ramp input. The modified value of the steady state error is 0.25. What was the initial value?

(a) 0.05

(b) 0.1

(c) 0.15

(d) 0.2

I got this question during an internship interview.

My question is based upon Steady State Error topic in section Error Analysis of Control Systems

Answer 1

Correct choice is (d) 0.2

Easy explanation: The integrator is similar to the phase lag systems and it is used to reduce or eliminate the steady state error and when it is cascaded with the ramp input. We know that when unit integrator is applied with a ramp input the steady state error will automatically increase but here we wanted the initial value which will be obviously less than the modified steady state error and by the same proportion.