Adaptive Control of Systems with Fast Varying Unknown Delay in Measurements

An adaptive output feedback controller with a fast varying unknown delay in the measurements is considered. Sufficient conditions for the resulting closed-loop system to be asymptotically stable with respect to state variables within some domain of attraction are derived. It is shown that the adaptive gain tends to a constant value. The proof is based on Passification lemma and a Lyapunov-Krasovskii method. The result is applicable to systems with polytopic-type uncertainties. Advantages of the adaptive control over the static output feedback are demonstrated on a pitch angle control of a flying vehicle.