Tuning of a Simulation Model for the Assessment of Functional Safety over Wi-Fi

In recent years, Factory Automation is evolving towards the so-called Industry 4.0, and the creation of a smart factory ecosystem comprising of ubiquitously interconnected objects, namely the Industrial Internet of Things (IIoT), is gaining much research interest. This paradigm aims at developing new smart technological equipment and protocols, thus providing interconnection among “factory objects” anywhere and at any time. In this context, people and machines have to safely cooperate and a high level of protection needs to be guaranteed for both operators and the surrounding environment. For this reason, safety systems, aiming at decreasing risks and failure probabilities, are nowadays of uttermost importance. Several Functional Safety communication protocols have been developed during these years pointing to increase data integrity and guarantee protection in a safety system. Popular examples are Fail Safe over EtherCAT (FSoE), ProfiSAFE, and OPC-UA Safety. These protocols, although conceived for wired networks, can be in principle adopted also by wireless communication, as they are developed by using a black channel approach. Nevertheless, the implementation of these protocols over different wireless networks is challenging as they might not ensure the required Safety Integrated Level (SIL). This paper, moving from the aforementioned observations and the need for wireless solutions in the IIoT context, focuses on proposing a possible implementation of FSOE over Wi-Fi, running UDP at the transport layer. In particular, by using suitable experimental outcomes, an OMNeT++ simulator has been calibrated, thus enabling the possibility to analyze the proposed protocol in wide industrial systems.