I'm doing my project on modern control system and had already design my circuit as below. The problem I'm facing is to eliminate the steady steady error. The steady state error is the second picture. I know that this is a first order system and in order to eliminate the steady state error, I need to add another integrator circuit. But I dont know how to calculate the values and also which type of integrator to use, i know there are two types which is inverting and non inverting but i dont know how to choose between these two types. The requirements is to eliminate the error without changing the original circuit which is can only add another circuit outside the circuit below and with the output still monitored. If a circuit need to be added, where is it need to be? After the Vin or need to have a summing amplifier with the input with some feedback?