  This paper investigates the target tracking problem for networked robotic
systems (NRSs) under sampled interaction. The target is assumed to be
time-varying and described by a second-order oscillator. Two novel distributed
controller-estimator algorithms (DCEA), which consist of both continuous and
discontinuous signals, are presented. Based on the properties of small-value
norms and Lyapunov stability theory, the conditions on the interaction
topology, the sampling period, and the other control parameters are given such
that the practical stability of the tracking error is achieved and the
stability region is regulated quantitatively. The advantages of the presented
DCEA are illustrated by comparisons with each other and the existing
coordination algorithms. Simulation examples are given to demonstrate the
theoretical results.
