ROBUST STABILITY AND PERFORMANCE ANALYSIS OF SAMPLED-DATA SYSTEMS

This paper considers the robust stability and performance analysis of a general linear interconnection of a continuous-time plant and a discrete-time controller via sample and hold devices. We obtain necessary and sufficient conditions for the robust stability of the feedback system consisting of an uncertain plant represented as a known linear time-invariant (nominal) model with time-varying norm bounded uncertainty and a shift invariant, discrete-time controller. These results show that the condition arising from the small gain theorem is necessary and sufficient when the uncertainties belong to a class of linear systems. Also similar results are derived for the case of structured uncertainty. Both L2 and L(infinity) signal norms are considered. Robust performance analysis problem is solved by converting it to a robust stability analysis problem.