Fractional Order Robust Controller for Fractional-Order Interval Plants

Fractional order (FO) calculus in modelling and control applications has been increasingly popular in every scientific field due to its versatility and superiority in various instances. Moreover, the models' parameters present uncertainties, called intervals. However, the main issue of fractional order elements is related to their implementation. Usually, integer order elements are used through different approximation methods to implement such elements. None of the existing methods discuss the introduction of a fractional element in a fixed-structure robust synthesis method. The objects from the MATLAB's Robust Control Toolbox could not be implied in other than well-known arithmetic operations between the parameters of the fixed-structure controllers, while existing approximations use exponential terms. To overcome this shortcoming, this work proposes and offers the algorithm for an approximation method useful in robust controller synthesis, which is validated for several numerical case studies. Copyright (C) 2022 The Authors.