D-stability problem of discrete singularly perturbed systems

The D-stability problem of discrete time-delay singularly perturbed systems is examined. A two-stage method is first developed to analyse the stability relationship between a discrete time-delay singularly perturbed system and its corresponding slow and fast subsystems. Finally, the upper bound of a singular perturbation parameter is derived such that D-stability of the slow and fast subsystems can imply that of the original system, provided that the singular perturbation parameter is within this bound. This fact enables us to investigate the D-stability of the original system by establishing that of its corresponding slow and fast subsystems.