Optimal Tuning for Fractional Order Controllers: An Integer Order Approximating Filter Approach

Abstract

This paper offers a systematic framework for the design of suboptimal integerorder controllers based on fractionalorder structures. The proposed approach is built upon the integerorder approximations that are traditionally used to implement fractionalorder controllers after they are designed. Accordingly, the fractionalorder structures are exploited to derive a suitable parameterization for a fixedstructure integerorder controller. The parameters, which describe the structure of the fixedorder integer controller, are the same as those used to describe the original fractional structure. Optimal tuning is then performed in the parameter space of the fractional structure and the resultant set of optimum parameters will determine the optimal integerorder controller. The proposed approach outperforms traditional implementations of optimal fractional controllers and presents an alternative that attempts to capture merits of both fractionalorder and integerorder structures.