PID Controller Response Curves:

You have to notice that these response curves are drawn supposing no corrective action is taken through the control system. Within actuality, as soon as the outcome of the controller starts to reposition the last control element, the magnitude of the error should starts to decrease. Finally, the controller will bring the error to zero and the controlled variable back to the setpoint.

Figure demonstrates the combined controller response to a demand disturbance. A proportional action of the controller stabilizes the procedures. The reset action combined along with the proportional action causes the measured variable to return to the setpoint. The rate action combined within the proportional action decreases the initial overshoot and cyclic period.

Figure: PID Controller Response Curves