Fractional-order control and interval analysis of SISO systems with time-delayed state

The control of time-delayed perturbed systems is easy when time delay affects system inputs or outputs. In the more difficult case when system states are affected, CRONE (fractional order) control-system design (CSD) methodology can be adapted and used. Stability analysis is achieved using interval analysis. An academic time-delayed system is used to illustrate the robust CSD methodology and the robust stability analysis. In order to provide a reduced-order robust controller, a reduced-order Padé approximation of the nominal system is selected as the nominal plant.