A New Approach to

This paper presents several new robust stability conditions for linear discrete-time systems with polytopic parameter uncertainties and time-varying delay in the state. These stability criteria, derived by defining parameter-dependent Lyapunov functions, are not only dependent on the maximum and minimum delay bounds, but also dependent on uncertain pa-rameters in the sense that different Lyapunov functions are used for the en-tire uncertainty domain. It is established, theoretically, that these robust sta-bility criteria for the nominal and constant-delay case encompass some ex-isting result as their special case. The delay-dependent and parame-ter-dependent nature of these results guarantees the proposed robust stability criteria to be potentially less conservative