Robustness of Feedforward Notch and Sallen-Key Compensators used with Second-Order Process

Copyright © 2014 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT: Robustness is one of the requirements used in controllers and compensators design. This paper examines the robustness of a Notch and a Sallen-Key compensator when used to control a highly oscillating second-order process. A variation of ± 20 % in process parameters is considered through simulation to study its effect on the system performance parameters using the tuned compensators. With a feedforward notch compensator, the variation in process damping ratio has small effect on the settling time, maximum percentage overshoot, and phase margin of the control system, while the change in the process damping ratio has a clear effect on the control system performance. For a negative change in the process parameters, the control system is unstable. With the Sallen-Key compensator, the control system is stable for the whole range of the process parameters variation ( ± 20 %). The change in the process damping ratio has a minor effect on the control system settling time, maximum percentage overshoot and phase margin. The change in the process natural frequency has a minor effect on the control system settling time and maximum percentage overshoot. The phase margin changes in the range 40-47 degrees corresponding to the ± 20 % change in process natural frequency