The PI controller is a widely used closed-loop controller for controlling a first-order system. The basic functionality of a PI controller is to make the feedback measurement to track the reference input. PI controller performs this action controls its output until the error between the reference and feedback signals becomes zero. There are two components that contribute to the output: the proportional term and the integral term, as shown in the following figure. The proportional term depends only on the instantaneous value of the error signal, whereas the integral term depends on the present and previous values of an error.