Simple conditions for robust stability of positive discrete-time linear systems with delays

The paper is devoted to the problem of robust stability of positive linear discrete-time systems with delays in the case of structured perturbations of state matrices. Simple new necessary and sufficient conditions for robust stability in the general case and in the case of system with linear uncertainty structure are established for two sub-cases: 1) unity rank uncertainty structure, 2) non-negative perturbation matrices. It is shown that robust stability of the positive discrete-time linear system with delays is equivalent to: 1) robust stability of the corresponding positive system without delays of the same order as time-delay system - in the general case, 2) asymptotic stability of finite family of the positive vertex systems without delays - in the case of a linear unity rank uncertainty structure, 3) asymptotic stability of only one positive vertex system without delays - in the case of a linear uncertainty structure with non-negative perturbation matrices.