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Networking: New encoder profile for SERCOS III

22 May 2009

A specification for this real-time Ethernet protocol is being developed and will be available November 2009.

According to the group SERCOS International, a specification for an encoder profile for the SERCOS III real-time Ethernet protocol is being developed in consultation with users and suppliers and will be available in November 2009. In parallel, a conformance test is being developed to ensure interoperability of different devices.

SERCOS (SErial Real-time COmmunication System) is a digital interface for communication between controls, drives and decentralized peripherals. In the first and second generation SERCOS interfaces, absolute and incremental encoders were connected to the servo drives or to the control system via a separate fieldbus, and not directly to the real-time bus. Because of the universal use of real-time Ethernet-based SERCOS III, there has been a demand to directly integrate encoders into a SERCOS III network, according to Ronald Larsen, managing director, SERCOS North America.

The new encoder profile ensures that the functions of an encoder – absolute or relative – are made available via clearly defined vendor-independent interfaces. The profile defines the functions supported by a device and how these functions may be used by other devices, such as control systems or servo drives.

Peter Lutz, managing director of SERCOS International, perceives the encoder profile as a very important extension to the existing profiles for servo drives and decentralized I/Os. “When defining the profile, we are considering existing parameters for encoders built into servomotors that are already part of the SERCOS drive profile. We are also making sure that the requirements of the encoder manufacturers are incorporated, especially with regard to their experience with existing, comparable device profiles of other bus systems.“

History 1, 2, 3: SERCOS I was internationally standardized in 1995, and the faster and more flexible SERCOS II was standardized in 1999. With the third generation, SERCOS III, speed is again increased, and it enables use of both fiber optic and CAT-5 copper cables. SERCOS III transfers data packets via the Ethernet and the TCP/IP protocol, and includes numerous safety functions in combination with a full-duplex transmission to assure trouble-free real-time operation of the communication system.

– Edited by Renee Robbins, senior editor
Control Engineering News Desk


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