Software Sercos master avoids the need for custom chips
At the recent SPS IPC Drives show in Germany, Sercos International (SI) demonstrated a software-based Sercos III master that avoids the need to use a hardware master based on FPGA or ASIC chips. Instead, the Sercos III hardware functions are emulated in host-based driver software running on a standard Ethernet controller.
Sercos International says that the Sercos III SoftMaster can deliver real-time behaviour in many applications. It adds that if an Ethernet controller with several queues and telegram scheduling (such as an Intel i210) is used, the software system can achieve synchronicities and availabilities similar to those of a hardware-based master.
SI has developed the SoftMaster core in cooperation with Bosch Rexroth and plans to make it available as open-source software. The license model will be based on the CoSeMa Sercos master library which has been available as open-source driver software since 2009 and can be used both for hard-master and SoftMaster implementations.
On SI’s stand at the SPS show, a German supplier of soft CNC, motion, and robotics systems, Industrielle Steuerungstechnik (ISG), was demonstrating a PC-based pick-and-place robotics application that implemented the Sercos SoftMaster on a Tenasys “Intime for Windows” real-time platform. The motion was programmed in the Multiprog SoftPLC programming environment using PLCopen-based function blocks.
SI reports that some “renowned” companies are already implementing projects based on the Sercos III SoftMaster. They include a packaging machine manufacturer that is said to be planning to convert all of its machines to the new technology before the Interpack 2017 exhibition. The company can now control its machines using industrial PCs without needing special fieldbus hardware or PCI slots. According to SI, using the software-based master with the Intel i210 chips has allowed the company to cut costs and save space, while also reducing CPU loads “significantly”.
“With the provision of a Sercos III SoftMaster implementation as an open source, it becomes much, much easier for manufacturers to develop a Sercos III master and at the same time to participate in future improvements and expansions of the software,” says Sercos International’s managing director, Peter Lutz. “In this way, control systems can be designed more affordably and are more simple and compact in the future. This is a very important criterion.”
• Sercos International has also released version 1.0 of its OPC Unified Architecture (UA) Companion Specification for Sercos, describing the mapping of the Sercos information model to OPC UA so that functions and data of Sercos devices can be made available via OPC UA. The aim is to simplify communications between machine periphery and supervisory IT systems, supporting the requirements of Industry 4.0 regarding semantic interoperability.
The mapping rules can be used for different architectures. For example, OPC UA server functions can be implemented in a Sercos master device (such as a CNC or PLC). It is also possible to implement the functions in a Sercos slave device. In the latter case, the OPC UA accesses are executed in parallel with Sercos real-time communications – or without any Sercos real-time communications.