Over the course of the last two decades, it has become hard to keep track of the numerous fieldbus systems that have been developed in the automation industry specifically for purposes of process and factory production control. Yet there remain various restraints that are impeding their performance. Demand has therefore become more pressing for a reliable communication system that would offer high flexibility and across-the-board compatibility. A new solution in this vein was also expected to allow for ongoing improvements and future upgrades. Ethernet was the first to rise to this challenge: it was a tried and tested technology that was free of patents and widely standardized to boot. Moreover, it had great potential to serve as a consistent, integrated communication solution that could support the interconnection of the control, process and field levels. Nevertheless, standard Ethernet in combination with an Internet protocol like TCP/IP is unsuitable for data transmission in hard real time. Data traffic can be delayed in unforeseeable ways due to the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) mechanism. An integral part of the Ethernet standard IEEE 802.3, this mechanism helps prevent data collisions on the bus that can occur in Ethernet environments due to the particular nature of Ethernet transmissions. In order to develop Ethernet-based, but real-time capable fieldbuses, manufacturers have pursued various approaches in their efforts to eliminate such delays. These solutions are commonly referred to as “real-time industrial Ethernet” technologies. POWERLINK has become one of the most successful real-time industrial Ethernet systems in the world today.
The Ethernet POWERLINK Standardization Group (EPSG) is an independent organization founded in 2003 by leading companies of the automation industry. Its aims are the standardization and further development of POWERLINK, which was first introduced by B&R in 2001. The high-performance real-time communication system is a protocol extension of the IEEE 802.3 Ethernet standard, designed to ensure real-time data transfer on the microsecond level. With openSAFETY, the EPSG has introduced in 2010 the world's first 100% open safety protocol. In fact, openSAFETY is open not only in terms of its legal basis, but also literally open in technical respects: given the protocol's busindependence. openSAFETY can be used with all fieldbusses, Industrial Ethernet solutions, or industry-specific communication solutions.