  This paper proposes a supervisory control structure for networked systems
with time-varying delays. The control structure, in which a supervisor triggers
the most appropriate controller from a multi-controller unit, aims at improving
the closed-loop performance relative to what can be obtained using a single
robust controller. Our analysis considers average dwell-time switching and is
based on a novel multiple Lyapunov-Krasovskii functional. We develop stability
conditions that can be verified by semi-definite programming, and show that the
associated state feedback synthesis problem also can be solved using convex
optimization tools. Extensions of the analysis and synthesis procedures to the
case when the evolution of the delay mode is described by a Markov chain are
also developed. Simulations on small and large-scale networked control systems
are used to illustrate the effectiveness of our approach.
