SERCOS interface celebrates 20th anniversary

By Control Engineering Staff November 16, 2005
Celebrants at SERCOS interface’s 20th anniversary were—from left to right: Prof. G. Pritschow (ISW, University of Stuttgart), H. Häckh (Walter Machines), P. Lutz (managing director of Interest Group SERCOS Interface e.V.), R. Graf (Num Guettinger), and D. Hagemann (VDW).

At the recent EMO machine-tool show in Hannover, Germany, supporting trade associations for SERCOS interface—serving digital controls, drives, I/O devices, and sensors— commemorated 20 years of successful development and application. Currently, SERCOS claims more than 1.5 million nodes installed worldwide in over 300,000 applications.

SERCOS was developed as a digital-drive interface in the mid-1980s by an industry consortium led by two German machine tool and electronics trade organizations. It progressed from a 1st-generation interface, supporting 2 and 4 Mbit/s transmission rates, to 2nd-generation SERCOS with 8 and 16 Mbit/s data rates (launched in 1999) and extended service channel for transmission of asynchronous data. The newer technology, based on SERCON816 ASIC, including backward compatibility to the first generation, became available in 2001.

Collision-free data transmission of 2nd-gen SERCOS, based on a time slot-mechanism, together with its efficient communications protocol, is said to ensure high performance and best possible determinism. ‘This hardware-based synchronization is prerequisite for reliable implementation of challenging motion applications, such as electronic line shafts in printing machines, packaging machines, and multi-axis machine tools,’ according to the SERCOS organization.

Ethernet-based SERCOS III, the newest development, was started in 2003. It uses the cyclic data transfer principle ‘with an accurate time pattern and a hardware-based synchronization.’ SERCOS III is defined to allow transmission of any standard IP telegram (for example, TCP/IP) in a non-real-time slot in parallel to real time processing. ‘Thus, SERCOS III combines established real-time mechanisms of SERCOS with universal communication based on Ethernet, says the organization. Besides increased performance, other new features have been specified, such as cross communication between controls, hardware redundancy, and hot plugging.

Led by Interest Group SERCOS interface (Stuttgart, Germany), the concept of SERCOS III was specified by a multi-company working group. The development reportedly ensures best possible backward compatibility to protect users’ and suppliers’ investments, while allowing easy migration to the new technology. First SERCOS III servo drive and motion control products are expected to be commercially available in late 2005 or early 2006.

SERCOS interface was recognized as international standard IEC 61491 in 1995.

Frank J. Bartos, executive editor, Control Engineering,