A discrete-time framework for stability analysis of nonlinear networked control systems

In this paper we develop a prescriptive framework for the stabilising controller design based on approximate discrete-time models for nonlinear Networked Control Systems (NCSs) with time-varying sampling intervals, large time-varying delays and packet dropouts. As opposed to emulation-based approaches where the effects of sampling-and-hold and delays are ignored in the phase of controller design, we propose an approach in which the controller design is based on approximate discrete-time models constructed for a set of nominal (non-zero) sampling intervals and nominal delays while taking into account sampling-and-hold effects. Subsequently, sufficient conditions for the global exponential stability of the closed-loop NCS are provided

A discrete-time framework for stability analysis of nonlinear networked control systems

In this paper we develop a prescriptive framework for the stabilising controller design based on approximate discrete-time models for nonlinear Networked Control Systems (NCSs) with time-varying sampling intervals, large time-varying delays and packet dropouts. As opposed to emulation-based approaches where the effects of sampling-and-hold and delays are ignored in the phase of controller design, we propose an approach in which the controller design is based on approximate discrete-time models constructed for a set of nominal (non-zero) sampling intervals and nominal delays while taking into account sampling-and-hold effects. Subsequently, sufficient conditions for the global exponential stability of the closed-loop NCS are provided

Scheduling of over-Actuated networked control systems

We investigate the scenario where an over-Actuated plant is controlled over a network. We concentrate on the effect of two network-induced phenomena: varying transmission intervals and scheduling, in the sense that only one of the actuators receives new data at each transmission instant. We present an emulation-based solution for the controller design, i.e., the controller is first designed to stabilize the origin of the plant ignoring the network and second, the packet-based network is taken into account and conditions on the maximum allowable transmission interval (MATI) and the scheduling protocol are given to preserve the stability of the closed-loop system. Our results are tailored to over-Actuated plants leading to significant improvements compared to applying off-The-shelf results available in the literature. In particular, a new model is derived and new conditions on the scheduling protocol are given, which lead to a two-measure stability property for the networked control system. We illustrate how new classes of scheduling protocols can be derived by exploiting over-Actuation, which leads to larger MATI bounds compared to applying existing results, as shown on a numerical example

Selection of electrode area for electrochemical noise measurements to monitor localized CO<inf>2</inf> corrosion

The simultaneous fluctuations of potential noise and current noise between two nominally identical X-65 mild steel electrodes were recorded using a ZRA (Zero Resistance Ammeter) to monitor localized CO 2 corrosion in CO 2 -saturated 1 wt% NaCl solution at 80°C. Electrochemical noise (EN) was obtained from both 11.6 cm 2 and 1 cm 2 specimens to understand how the surface area affects EN signals. Linear polarization resistance (LPR) measurements were conducted to investigate the general CO 2 corrosion behavior. Surface morphologies and pit depths were observed by scanning electron microscopy (SEM) and infinite focus microscopy (IFM) for 3D optical analysis. The results showed that the electrode area significantly influenced the EN signals of localized CO 2 corrosion. Transients related to metastable pitting were best observed with 1 cm 2 specimens but not clearly obtained for 11.6 cm 2 specimens. © 2012 The Electrochemical Society