On Stabilization of Nonlinear Time-Delay Systems via Quantized Sampled-Data Dynamic Output Feedback Controllers

In this paper we deal with the stabilization problem of nonlinear systems affected by state delays and known time-varying disturbances via quantized sampled-data dynamic output feedback (QSDOF) controllers. In particular, a QSDOF controller for nonlinear time-delay systems is proposed by means of the novel notion of Dynamic Output Steepest Descent Feedback (DOSDF) induced by a general class of Lyapunov-Krasovskii functionals. Then, the theory of the stabilization in the sample-and-hold sense is used in order to show that: there exist a suitably small inter-sampling time and a suitably accurate quantization of the input/output channels such that the semi-global practical stability of the related quantized sampled-data closed-loop system is ensured with arbitrarily small final target ball of the origin. In the theory here developed, time-varying sampling intervals as well as non- uniform quantization of the input/output channels are taken into account. Furthermore, the stable inter-sampling system behaviour is proved. The case of non-linear delay-free systems is addressed as a special case. An example is presented which validates the theoretical results.