Tracking control for sampled-data systems with uncertain time-varying sampling intervals and delays

In this paper, a solution to the approximate tracking problem of sampled-data systems With Uncertain, time-varying sampling intervals and delays is presented. Such time-varying sampling intervals and delays call typically occur in the field of networked control systems. The Uncertain, time-varying sampling and network delays cause inexact feedforward, which induces a perturbation oil the tracking error dynamics, for which a model is presented in this paper. Sufficient conditions for the input-to-state stability (ISS) of the tracking error dynamics with respect to this perturbation are given. Hereto, two analysis approaches are developed: a discrete-time approach and an approach in terms of delay impulsive differential equations. These ISS results provide bounds oil the steady-state tracking error as a function of the plant properties, the control design and the network properties. Moreover, it is shown that feedforward preview call significantly improve the tracking performance and in online extrCITILIM seeking (nonlinear programming) algorithm is proposed to online estimate the optimal preview time. The results are illustrated oil a mechanical motion control example showing the effectivcness of the proposed strategy and providing insight into the differences and commonalities between the two analysis approaches. Copyright (C) 2009 John Wiley & Sons, Ltd.