INDUSTRIAL COMMUNICATION How did you develop the study and the demonstrator? Michael Kessler: From the very beginning, it was clear to us that the existing Ethernet technology is not suited to the special conditions in the process industry. That is why we carried out a detailed study on this topic a few years ago. As a member of the APL consortium, we then took the initiative and translated the results of this study into our demonstrator. On a small scale, it represents the typical communication architecture of a processing plant with Ethernet signal transfer, and shows that Ethernet can fulfill the requirements of the process industry for use in the field. We have exhibited our demonstrator at the ‘Hanover Fair’ and ‘Achema’. I have been to numerous trade fairs in the past 28 years, and I have never experienced a level of interest like this exhibit received. Many visitors came several times, with new questions each time, and they usually brought colleagues with them. What kind of bandwidth can be achieved? Michael Kessler: We can reach up to 10 Mbit/s. This is more than 8,000 times greater than ‘Hart’ protocol, and still more than 300 times the transfer rate of ProfiBus PA or ‘Foundation Fieldbus’. It also means that we can manage the volumes of data that would be generated in an Industry 4.0 environment. And since we’re talking about Industry 4.0, how important is the APL for this? Lutz Liebers: We believe it is a crucial pre-requisite. In process automation, Industry 4.0 works only if it can successfully transmit large volumes of data from the field level of the process plants into the Industry 4.0 architecture information level. The pre-requisite for this is a uniform communications architecture across the plant that does not require network transitions. Are we therefore about to see a significant shift in process automation? Lutz Liebers: Plants in process industries are designed for decades of operation. For this reason alone, there will be no rapid conversion on a large scale. However, a gradual migration is part of the concept—the cabling remains unchanged; and combining Ethernet with conventional fieldbus devices is possible. I am sure that traditional and IP-based technologies will exist alongside each other for a long time. What would functioning PA Ethernet mean to the users of field devices and sensors? Lutz Liebers: Users will be able to take full advantage of the wealth of information provided by modern field devices. Ethernet bridges the gap for process automation to Sensorik 4.0 (sensor technology), which we see as an essential foundation for Industry 4.0. The PA Ethernet Demonstrator from Pepperl+Fuchs represents the typical communication architecture of a process plant. The devices have their own web servers, and the entire wiring takes the form of a two-wire fieldbus cable that transfers data and energy. A field switch for hazardous areas provides intrinsically safe ports for connecting the Ethernet-enabled field devices. The signal transfer is compatible with all Ethernet protocols. The cabling for ProfiBus PA and ‘Foundation Fieldbus’ can be used, and conventional fieldbus devices can be connected to the field switch directly. Photographs: Fotolia background, Pepperl+Fuchs GmbH www.pepperl-fuchs.com About Pepperl + Fuchs Pepperl+Fuchs is a worldwide company with its headquarters in Mannheim, Germany. They manufacture products for Factory and Process Automation and are specialists in sensor manufacturing. With revenues more than € 500 million and nearly 5,600 employees worldwide, the company has more than 40 foreign subsidiaries on six continents, and manufacturing facilities in Germany, USA, Singapore, Hungary, China, Indonesia and Vietnam. The Factory Automation Division is a manufacturer of industrial sensors designed to address specific market needs. It makes a range of inductive, capacitive, photoelectric, and ultrasonic sensors as well as identification systems, barcode and camera systems, rotary encoders, position measurement systems. The Process Automation Division is a leading organization in intrinsically safe explosion protection components and protection of hazardous area applications.
Successful OPC UA Sercos model – a commentary by Peter Lutz Performance and real-time features are often negatively impacted in classical, Ethernet-based communication protocols. In contrast, a smooth information exchange can be implemented with OPC UA technology and multiprotocol characteristics of Sercos transfer method. The user request for a cross-company networking and seamless access to production-relevant data for devices at field level is made difficult by the heterogeneous bus landscape in automation and lack of cross-bus standards. In fact, many manufacturers are implementing Industrial Ethernet solutions. However, even if the technical advantages are evident, they do not make functioning systems based on traditional field buses obsolete automatically. In addition, there is a whole series of competing communication protocols, which are based on Ethernet, but are not compatible with reference to the communication protocol and the device profiles used. Furthermore, we also have to consider that most of the communication protocols cannot coexist in a common network infrastructure without being affected negatively from a performance and real-time characteristics perspective. From company to field level The OPC Unified Architecture (OPC UA) technology represents a universal communication standard, which allows networking of the systems from the company level to controller or field level. OPC UA can be integrated on any platform with different programming The Sercos automation bus The Serial Real-time Communication System, Sercos in short, is one of the leading digital interfaces for communication between controllers, drives and decentralised peripheral devices. Sercos has been deployed in mechanical engineering for approx. 25 years and is implemented in more than 5 million real-time nodes. With the open, manufacturerindependent architecture based on Ethernet, Sercos III provides a universal bus for automation solutions. languages and even any complex system can be represented completely with the help of the OPC UA Information Model. Even though OPC UA is practically a communication standard, which extends from the company level to the field level, there are two significant limitations. On the one hand, OPC UA can replace existing field bus and Industrial Ethernet systems only if there are no time-bound and deterministic requirements for communication. On the other hand, OPC UA only defines how data is described and exchanged. The actual meaning of data (semantics) is not defined. Communication between field devices in real-time The above reasons provide a promising approach to implement profiles and services defined by field buses and real-time Ethernet systems on OPC UA. Thus, the process and device data will be uniform and they will not be available just locally via field bus systems, but also through any other higher network infrastructure via OPC UA. The fact that OPC UA can be used for information exchange with individual field devices without having to forego real-time and quick data transmission proves the multi-protocol characteristics of the Sercos transfer method, because it is possible to transfer OPC UA in parallel with Sercos real-time communication. An OPC server can be directly integrated in a field device (drive, I/O station or sensor). The OPC protocol is routed directly to the respective slave device without impairing the real-time characteristics. The communication capability between an OPC client and an OPC UA server is retained even for deactivated Sercos communication due to the transfer method (co-existence, no tunnelling!). www.sercos.org About Sercos International e.V. Author: Peter Lutz is CEO of Sercos International e.V., Suessen, Germany Sercos International is an association of users and manufacturers, who are responsible for the technical development, standardisation, certification and marketing of the Sercos automation bus. The organisation is headquartered in Germany and has more than 90 companies as members and has regional representation in North America and Asia. AUTOMATION TECHNOLOGIES 1/2016