  Sampling arises simultaneously with input and output delays in networked
control systems. When the delay is left uncompensated, the sampling period is
generally required to be sufficiently small, the delay sufficiently short, and,
for nonlinear systems, only semiglobal practical stability is generally
achieved. For example, global stabilization of strict-feedforward systems under
sampled measurements, sampled-data stabilization of the nonholonomic unicycle
with arbitrarily sparse sampling, and sampled-data stabilization of LTI systems
over networks with long delays, are open problems. In this paper we present two
general results that address these example problems as special cases. First, we
present global asymptotic stabilizers for forward complete systems under
arbitrarily long input and output delays, with arbitrarily long sampling
periods, and with continuous application of the control input. Second, we
consider systems with sampled measurements and with control applied through a
zero-order hold, under the assumption that the system is stabilizable under
sampled-data feedback for some sampling period, and then construct sampled-data
feedback laws that achieve global asymptotic stabilization under arbitrarily
long input and measurement delays. All the results employ "nominal" feedback
laws designed for the continuous-time systems in the absence of delays,
combined with "predictor-based" compensation of delays and the effect of
sampling.
