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Industrial Ethernet Book 99

Technology time of 1 to 5 ms. Since this communication is used to handle control tasks, latency needs to be very low. Non-critical communication also takes place between the robot and the tool control system – when exchanging data with an MES or a database, for example. Cyclic communication between machine control system and transport vehicle/carrier: Cyclic communication between the control system and mobile devices is required for transporting material to the plant. The target range for communication cycle times is 1 to 5 ms. Low latency ensures no side-effects occur when issuing commands to mobile devices. Non-critical communication takes place between the tool control system and carrier. The two use cases described above are particularly difficult to implement by message transmission between a sender and a receiver, as is envisaged by the client/server model. For this reason, the OPC UA standard is currently being adapted to include a publisher/ subscriber communication model that is particularly suited to the transmission of multicast and broadcast messages. Depending on the use case, various implementations of the OPC UA publisher/ subscriber communication model are possible. When implementing the IIoT use cases presented, all of which require a fast local network, the ideal option is to use connectionless secure communications based on the User Datagram Protocol (UDP) secure multicast network protocol. This enables the implementation of a lean and efficient protocol stack for message handling, while also supporting cyclic data exchange. This type of communication is characterized by low network loads in conjunction with the rapid and reliable exchange of data. The specified OPC UA information model does not need to be modified in this scenario. Simple deployment of the OPC UA publisher/ subscriber model alone cannot yet be used to implement all of the use cases. This is due to the need to provide support for deterministic data exchange. One possible solution here is the use of time-sensitive networking (TSN) standards for industrial Ethernet networks. This uses globally synchronized time responses in conjunction with a common schedule for all network components. Since this enables time slots to be reserved for the transmission of prioritized messages, this results in the provision of a guaranteed upper limit to the maximum latency of planned data traffic in a switched network. IIoT feasibility study In conjunction with the time-sensitive networking standard, the OPC UA publisher/ subscriber model is theoretically capable of supporting the deterministic exchange of data required by IIoT implementations. Before deploying these two technologies in real-world applications, however, the practical feasibility of this approach must be verified. For this reason, Softing set up a pilot facility for testing the timing performance of OPC UA publisher/subscriber communication within a TSN network. In designing this facility, Softing has applied over two decades of experience in OPC, combined with its universal device platform developed in-house on the basis of FPGA technology. This platform can be tailored to individual requirements simply by installing the right hardware and software on the FPGA. Softing used the pilot facility to conduct an initial practice-oriented evaluation of real-world deviations from the specified cycle Network MORE time. The results of this experiment showed that the use of time-sensitive networking can offer a significant improvement to deterministic time performance in the OPC UA publisher/subscriber communication model compared to standard OPC UA client/server communication. Increasing the network load does not create any communication problems. Other findings also showed that restricting messaging traffic did not result in a loss of bandwidth. This approach is an ideal solution to the special communication requirements for the IIoT applications discussed. Dipl.-Inform. Georg Suess, Operational Marketing, Softing Industrial Automation. IIoT Advantage: Industrial Ethernet for Network Reliability With over 100 mixed-media configuration options, Red Lion’s rugged NT24k® all-Gigabit managed industrial switches provide the ultimate in network flexibility. • Support varied options: Fast Ethernet, Gigabit, Copper, Fiber, SFP and PoE+ • Withstand extreme conditions with rugged environmental specs • Enable plug-and-play deployment thanks to auto-configuration Learn more today at www.redlion.net/Reliable-Networking or contact us at europe@redlion.net Connect. Monitor. Control. I www.redlion.net © 2017 Red Lion Controls, Inc. All Rights Reserved. Data. Devices. Locations. 31 4.2017 industrial ethernet book


Industrial Ethernet Book 99
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