Blended Sercos III and EtherNet/IP

Machine Builders and Users Reduce the Cost and Complexity of Machine Integration Resulting in Easier and Faster Implementation, Making It a Safer Process

By Peter Lutz

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The great variety of automation technology in today's world requires a new conceptual approach to simplify integration of machinery in manufacturing. A common network with a blended infrastructure enables machine builders and users to reduce the cost and complexity of machine integration. This results in easier and faster machine implementation and makes this process even safer. At the same time, machine builders and users retain the ability to use their preferred product suppliers and automation devices, so there is no need for any additional effort to research new suppliers and/or consider different automation devices.

Blended infrastructure means that various sercos III and EtherNet/IP devices use a common Ethernet infrastructure on a single cable. These can coexist in one network environment, so that sercos telegrams, CIP messages and TCP/IP telegrams run on one cable. The joint use of the network has no impact on the real-time behavior of the different protocols, thus the respective protocols remain fully functional. Only the bandwidth is shared between them.

However, for most applications, this does not result in any restrictions because sufficient bandwidth is available with 100 Mbps full-duplex Ethernet. To keep the cyclical and clocked communication of sercos intact, the CIP messages and TCP/IP telegrams are transmitted in the Unified Communication Channel (UCC), which is an integral part of the sercos transmission method, whereas the sercos telegrams are transmitted in a dedicated Real-Time Channel (RTC).

An increasing number of requests from industry led to this development. All the real-time Ethernet standards available today have areas of strength where they are supported, and many products are available for users. A single bus might not be the perfect solution for all of a project's needs, driving users to include multiple network buses in a design. For those systems, users want to reduce the variety of physical and structural cabling in machinery, thus reducing overall costs, increasing safety standards and streamlining processes. Together with the ODVA, we have been working on this since April 2012, and this blended infrastructure is one of the first results of the machinery initiative, in which sercos international, ODVA and OPC Foundation collaborate.

Sercos is an automation bus, designed for applications that require high speed in combination with high precision. The blended infrastructure approach complements our portfolio effectively by including general-purpose devices available for EtherNet/IP from other manufacturers. There are a wide variety of actuators and sensors used in general automation and process industries, which have only occasional uses in application areas where sercos dominates. With the blended infrastructure, those devices can be used in all application areas.

The blended infrastructure approach results in additional market opportunities for vendors of EtherNet/IP devices. Machine builders, control system builders and system integrators that use sercos for their applications today will preferably use EtherNet/IP as a complementary protocol. Especially on small, more motion-centric applications, where it could have been difficult in the past to justify dual-network systems, new opportunities will open up for EtherNet/IP vendors. The market acceptance and presence of EtherNet/IP will therefore increase in the machinery and plant engineering sector.

The great advantage of a blended infrastructure is that sercos III and EtherNet/IP devices can coexist in a common infrastructure at this time without any changes required to the devices. Only a few easy and well-defined installation rules need to be followed. However, a very interesting use case is to have a single controller that supports sercos III and EtherNet/IP concurrently (dual-stack master). Prototypes of such controllers from Bosch Rexroth and Schneider Electric — each connected to various sercos III and EtherNet/IP devices — were shown as part of the first blended infrastructure demonstration systems during the SPS IPC Drives exhibition in November in Nuremberg. Because the prototypes are already there, we expect to see the first products in the coming months.

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