Sercos interface celebrates 20th anniversary

Edited by the Engineeringtalk editorial team Nov 11, 2005

At the recent EMO machine tool show the Sercos trade associations commemorated 20 years of successful development and application of the Sercos interface for digital controls, drives, I/O and sensors.

At the recent EMO machine tool show in Hanover, Germany the Sercos trade associations commemorated 20 years of successful development and application of the Sercos interface for digital controls, drives, I/O and sensors.

At present, more than 1.5 million Sercos nodes have been implemented worldwide in over 300 thousand applications.

The Sercos interface was developed as a digital drive interface in the mid-1980s by an industry consortium under the leadership of two German machine tool and electronics trade organisations.

The first generation of the Sercos interface supported transmission rates of 2 and 4 Mbit/s and was mainly used in advanced machine tool applications.

In the following years Sercos became accepted worldwide as a universal motion control interface and has been used in all kinds of servo-driven applications.

In 1995, the Sercos interface was established as international standard IEC61491.

In 1999, the second generation of Sercos was launched, with the transmission rate increased to 8 and 16Mbit/s and the service channel for the transmission of asynchronous data extended.

This new technology has been available since 2001, based on the Sercon816 ASIC, while downward compatibility to the first generation was maintained.

The collision-free data transmission based on a time slot mechanism, together with the highly efficient communications protocol of the Sercos interface, ensures very high performance and the best possible determinism.

This hardware-based synchronisation is the prerequisite for the reliable implementation of challenging motion applications, such as electronic line shafts in printing machines, packaging machines and multi-axis machine tools.

Sercos not only defines a real-time communication system but also offers more than 400 standardised parameters that describe the interplay of drives and controls in terms independent of any manufacturer.

It has also become common to couple I/O stations to the bus, so that an additional fieldbus can be eliminated in many stand-alone machines.

In 2003, the development of a new Ethernet-based Sercos III began.

Sercos III is based on the established real-time mechanisms of the original Sercos interface and uses the principle of cyclic data transfer with an accurate time pattern and a hardware-based synchronisation.

Sercos III is defined such that any standard IP telegram (eg, TCP/IP) can be transmitted in a non-real-time slot in parallel to the real-time processing.

Thus, Sercos III combines the established real-time mechanisms of Sercos with universal communication based on Ethernet.

In addition to a significant increase in performance, many new trend-setting features have been specified, eg, cross communication between controls, hardware redundancy and hot plugging.

The Sercos III concept was specified by a multi-company working group under the leadership of the Interests Group Sercos interface in Stuttgart.

The development has insured the best possible backward compatibility in order to protect the investments of users and suppliers and to allow an uncomplicated migration to the new technology.

First Sercos III products will be commercially available in late 2005 or early 2006.