Turning PID controller tuning into a simple consideration of settling time

This article introduces an approach to PID tuning based solely on a physically meaningful performance specification: settling time. The approach leads to extremely simple tuning procedures which avoid potentially excessive excitation of the process. Provided that the closed loop system meets two necessary conditions, supplemented by a third condition in the PI case, the designer starts by choosing a desired settling time of the response to a step in the reference signal. The integral gain and derivative gain follow from a table look-up. The proportional gain is chosen as large as possible, except in the case of the PI controller. The controller settings define a reference model with the desired settling time chosen by the designer. Consequently, various processes can be tuned to converge to the same reference model response.