Improved robust stability criteria and design of robust stabilizing controller for uncertain linear time-delay systems

In this paper, an improved linear matrix inequality (LMI)-based robust delay-dependent stability test is introduced to ensure a larger upper bound for time-varying delays affecting the state vector of an uncertain continuous-time system with norm-bounded-type uncertainties. A quasi-full-size Lyapunov-Krasovskii functional is chosen and free-weighting matrix approach is employed. Less restrictive sufficient conditions are derived for robust stability of time-varying delay systems with norm-bounded-type uncertainties. Moreover, the investigation of the stabilization problem with memoryless state-feedback control is presented such that the stabilizability criteria are obtained in terms of matrix inequalities, which can be solved via utilizing a cone complementarity minimization algorithm. Finally, the problem of output feedback stabilization for square systems is also taken into consideration. The output feedback stabilizability criteria are derived in the form of linear matrix inequalities, which are convex and can be easily solved using interior point algorithms. A plenty of numerical examples are presented indicating that the proposed stability and stabilization methods effectively improve the existing results. Copyright (C) 2006 John Wiley & Sons, Ltd.