Robust Tuning for 2DoF Fractional-Order PI Controllers Based on Model Reference Approach

Abstract

AbstractThis work proposes a tuning methodology for a two-degree-of-freedom (2-DoF) fractional-order PI (\(FOPI_{2}\)) controller based on the Model Reference methodology presented by [1, 2]. The tuning rules are optimized for a first order plus dead time (FOPDT) model and for an over-damped servo and regulatory closed-loop target time responses. Moreover, the design takes into account a robustness consideration, expressed as a maximum sensitivity target value of 2.0, 1.8, 1.6 and 1.4; dealing with the performance/robustness trade-off of the closed-loop control system. A set of controller tuning equations (four parameters) is provided for FOPDT models with normalized dead-times from 0.1 to 2.0. Also, an evaluation of the control system performance and robustness is presented, in order to show the effectiveness of the proposed tuning method, that is compared with other tuning rules. The work extends a previous presented idea [15], for a new parameterization of the controller and more values for the target robustness.KeywordsPI controlModel ReferenceFractional controlTuning rules