SERCOS interface - third generation of standard is under development
SERCOS interface - third generation of standard is under development
Keywords: Motion control
The Interest Group SERCOS (IGS) interface has announced that the initiative"Next Generation SERCOS" (NGS) has been launched in order to further develop the SERCOS interface standard in the direction of using Industrial Ethernet.
SERCOS interface was originally developed as digital drive interface during the late 1980s by an industrial consortium with support by ZVEI (German Electrical Standards Association) and VDW (German Machine Tool Builders Association).
The first generation of SERCOS interface supported transmission speeds of 2 and 4Mbit/s and was primarily utilized in high-performance machine-tool applications. In the following years, SERCOS interface was successfully deployed world-wide in many different applications and by a multitude of vendors. In 1995, SERCOS interface was approved as international standard IEC 61491.
By 1999, the development of the second generation of the SERCOS interface standard was started. Among other features, the transmission speed was increased to 8 and 16Mbit/s, and the service channel for transmitting asynchronous data was extended. Still, the backward compatibility to the existing standard was retained. Since 2001 this technology is readily available for implementation using the SERCON816 ASIC.
The efficient communication protocol, in combination with the collision-free time division multiplex access (TDMA) procedure of SERCOS interface, allows very high performance with guaranteed real-time behavior. For example, up to 40 axes can be controlled and synchronized in hard real-time using a cycle time of 0.1ms with a jitter below 1 ms.
Consequently, SERCOS interface is the dominant solution when compared with other standards in drive communication, e.g. Profibus and CAN. Even"Fast-Ethernet" based approaches - despite a gross transmission rate of 100 Mbps- very often achieve no better performance and furthermore reveal limitations with regard to their real-time behavior.
SERCOS interface has become the recognized de facto standard for all highly dynamic motion control applications, with or without multi-axes synchronization, in many different industries. Over the years SERCOS interface has advanced from a specialized drive interface to a universal "motion control"interface. Not only drives, but more and more decentralized I/O stations are connected to the bus. For many stand-alone machines an additional field bus is not required. Furthermore, the SERCOS interface standard defines over 400 standardized parameters, which describe the interaction between controls and drives by a vendor-neutral semantics.
The planned extensions to SERCOS are:
(1) improving the ease of integration by supporting higher protocols from office and fieldbus communication (e.g. TCP/ IP, Profibus and CIP);
(2) improving the performance by introducing higher transmission speeds;
(3) improving the interoperability of control and drive components by defining "motion control" profiles and developing the associated test suites to assure conformance;
(4) cost reduction by applying appropriate technology standards.
The different working groups consist of representatives of the member companies of the SERCOS organization. They will develop proposals for extending the existing standard.
The described development is carried out under careful attention of 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.
