This specification was created by a joint working group of the OPC Foundation and the Ethernet POWERLINK Standardization Group (EPSG). It defines an OPC UA Information Model to represent the models from Ethernet POWERLINK.
The OPC Foundation defines standards for online data exchange between automation systems. They address access to current data (OPC DA), alarms and events (OPC A&E) and historical data (OPC HDA). Those standards are successfully applied in industrial automation.
The new OPC Unified Architecture (OPC UA) unifies the existing standards and brings them to state-of-the-art technology using service-oriented architecture (SOA). Platform-independent technology allows the deployment of OPC UA beyond current OPC applications only running on Windows-based PC systems. OPC UA can also run on embedded systems as well as Linux / UNIX based enterprise systems. The provided information can be generically modelled and therefore arbitrary information models can be provided using OPC UA.
Ethernet POWERLINK Standardization Group
The Ethernet POWERLINK Standardization Group (EPSG) was founded in 2003 as an independent association. Its goals are the standardisation, promotion and further development of POWERLINK technology, which was first presented to the public in 2001. POWERLINK is a patent-free, manufacturer-independent and completely software-based communication system for hard real-time that has been available as a free open source solution since 2008. The EPSG’s POWERLINK office handles public relations, coordinates the implementation of shared projects and provides information for existing and prospective members.
The EPSG is working closely with the CiA (CAN in Automation) organisation to integrate CANopen with POWERLINK. CANopen is one of the most widely used application protocols today. Key benefits of this protocol include standardised device description files that make status information, parameter configurations, device characteristics and other relevant data available in transparent form on the network. A major decision made by the EPSG was to define the protocol’s application layer as a carrier of all CANopen mechanisms. CiA, the international association of CAN users and manufacturers, was significantly involved in this development.
Ethernet POWERLINK uses the same concepts as CANopen for object dictionaries, device descriptions and communication mechanisms including process data objects (PDOs), service data objects (SDOs) and network management (NMT). As with CANopen, direct cross-traffic is also one of the essential features of POWERLINK. All CANopen applications and device profiles can be directly implemented in POWERLINK environments as well – the applications will not see a difference between the two protocols. For this reason, POWERLINK can also be referred to as “CANopen over Ethernet”.