Eric Rondeau

A formal method to guarantee a deterministic behaviour of switched Ethernet networks for time-critical applications

The objective of this work is to model a switched Ethernet architecture in order to be able to evaluate the maximum end to end delays. The major interest is to apply these results in an industrial or technical context, where some of the communications are strongly time-constrained. In this paper, we have chosen the network calculus theory, because it enables a good representation of the exchanges between the equipment which are connected to the network, and also to determine the maximum end to end delays. Previous models presented are improved in order to take into account the implementation of a classification of service (CoS) mechanism which enables to define priorities for the messages regarding the time constraints they have to respect This paper describes a new model of a IEEE 802.1p switch. It also presents the analytical formulas which upper bound the maximum time for crossing such a switch, and an algorithm to determine the maximum end to end delays of the time-critical messages over the whole network. A typical application shows the interest of this approach

USE OF UPPER BOUND DELAY ESTIMATE IN STABILITY ANALYSIS AND ROBUST CONTROL COMPENSATION IN NETWORKED CONTROL SYSTEMS

Abstract Recent interest in networked control systems (NCS) has instigated research in various areas of both communication networks and control. The analysis of NCS has often been performed either from the network, or the control point of view and not many papers exist were the analysis of both is done in the same context. Here an overall analysis is presented. In the paper the procedure of obtaining the upper bound delay value in the switched Ethernet network is proposed and the obtained delay estimate is used in stability analysis of the feedback loop and in the control compensation. The upper bound delay algorithm is based on the network calculus theory, the stability analysis uses the small gain theorem, and control compensating strategy is based on Smith predictor, where however the upper bound delay is utilised in obtaining the delay estimate.