Abstract:Energy is a key resource in Networked Control Systems, in particular in applications concerning wireless networks. This paper reviews the multi-layer architecture of those systems in the light of their energy-use, and points out major contributions in the area of energy-management policies, layer per layer. This review of the literature is organized according to the layered communication architecture covering from bottom to top the Physical, Data Link, Network, and Application layers. We specifically focus on advances that concern energy-aware management in wireless communication and control co-design. It is argued that existing work is limited to single layer approaches, with a lack of design methods taking into account several layers.

This document completes the paper "Smart Energy-Aware Sensors for Event-Based Control" submitted to the 51 st IEEE Conference on Decision and Control by the same authors. It is not intended to be self contained; it only gives the proof of Lemma 2.

Energy efficiency is one of the main issues in wireless Networked Control Systems. The control community has already shown large interest in the topics of intermittent control and event-based control, allowing to turn off the radio of the nodes, which is the main energy consumer, on longer time intervals than in the periodic case. While the existing literature only addresses policies using two radio-modes (Tx -Transmitting, and Sleep), this paper considers intermediate radio-modes, which consume more energy than the Sleep mode but have cheaper transition costs to the Transmitting mode. We propose an event-based radio-mode switching policy to perform a trade-off between energy saving and performance of the control application. To this end, we derive a switched model taking into account control and communication. We compute the optimal switching policy using Dynamic Programming and we illustrate the results in simulations.Index Terms-Networked Control Systems, event-based control, radio-mode management.

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International audienceThis paper addresses energy-aware control in a wireless control system. The goal is to save energy in a smart sensor node by co-designing its use of the radio chip together with the control policy. The focus is on exploiting the fact that in many radio-chips used in wireless nodes the depth of sleep can be manipulated dynamically. The choice of the mode involves a trade-off, since deeper sleep is cheaper to stay in, but leads to higher future transition costs. The opportunities arising from the use of multiple non-transmitting radio-modes have not been studied in the systems control literature. The present work presents a first step towards filling this gap. We propose a control scheme that manages the radio-modes of a single sensor node with computation capabilities. This smart sensor node is in charge of sensing the system state, computing the control law to be sent to the actuator, and managing its own radio chip. The joint optimization problem of finding the best switching policy for the radio-chip mode and the best feedback control law is obtained off-line using dynamic programming. The optimal policy is formulated over a finite horizon and implemented according to the model predictive control paradigm. Practical stability of the resulting control scheme is assessed and careful simulation studies document the potential energy savings that can be obtained with this technology