Robust H-infinity output feedback control of uncertain fractional-order systems subject to input saturation

This article considers the problems of robust stability and stabilization for a class of fractional-order linear time-invariant systems via 0 < alpha < I subject to input saturation with convex polytopic uncertainties, by a kind of H-infinity-proportional- integral-derivative control synthesis. A new saturation-based stability condition is suggested to estimate the stable region (B-epsilon) and region of attraction (epsilon) using the ellipsoid approach. The main concept of the presented strategy is based on transforming the proportional-integral-derivative controller design problem into the static output feedback control problem. Gronwall-Bellman lemma and sector bounded condition of the saturation function is used for stability investigation and stabilization of such systems. The static output feedback control laws are obtained with the aid of a non-iterative linear matrix inequality implication. From the static output feedback controller, the proportional-integral-derivative controller is then restored. Stability problem is addressed as an optimization problem to obtain the controller gains and the stable region, as well as the largest region of attraction. Some theorems and numerical examples are provided to illustrate the results of proposed mechanism.