Real-time networks and protocols for industrial automation
Lucia Seno · Padua Research Archive (University of Padova) · 2011
Nowadays, networks are fundamental elements for developing factory automation systems. In this thesis, we focus industrial communication networks (ICNs) employed at the device level, for the fast data exchange between controller and sensors/actuators, that are required to satisfy tight reliability and real-time requirements. In this context, the scenario is rapidly evolving. Indeed on the one hand, high performance and low costs are required to cope with more and more demanding requirements, while, on the other hand, real-time characteristics are needed in an increasing number of industrial automation applications. In the last years, two new types of ICNs have been introduced for device-level industrial communication. Besides fieldbuses, traditionally employed, both real-time Ethernet (RTE) networks, based on IEEE 802.3 standard, and wireless networks have become available. In this thesis we focus on Ethernet Powerlink, a popular RTE network. Firstly, we refer to the Ethernet Powerlink specifications and provide a description of the network and, in particular, of the data link layer protocol real-time features. We propose a modification to the protocol that allow the network to better manage real-time acyclic traffic and provide results of a relevant both theoretical and a simulative analysis. Subsequently we investigate possible wireless extensions of Ethernet Powerlink based on the IEEE 802.11 wlan and present results of both a theoretical and a simulative analysis relevant to two specific solutions. Finally we practically realize one of the two solutions and provide results of extensive measurements on the real system. We particularly focus on the comparison between theoretical, simulative and experimental results and on the influence of real components behavior on the overall performance of the system.