C5.2 - EtherCAT - The new standard for measurement applications - Central backbone for distributed systems
- SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
- Proceedings SENSOR 2009, Volume II
- C5 - Sensor Communication II
- J. Kessel - ADDITIVE Soft- und Hardware für Technik und Wissenschaft GmbH, Friedrichsdorf, Germany
- 185 - 188
In the past years EtherCAT has become a world wide accepted new standard in automation and control. In November 2003 the EtherCAT Technology Group (ETG) was founded and it has grown up to about 900 members from 45 countries in January, 2009. EtherCAT was designed and developed as an open high performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet technology to automation applications which require short data update times (also called cycle times) with low communication jitter (for synchronization purposes) and low hardware costs.
Once the new standard was introduced for automation and control, it became interesting, too, to use EtherCAT also for distributed systems in measurement applications.
This paper takes a focus on the special properties of EtherCAT with respect to the usability in measurement applications. It shows the capabilities of EtherCAT as a powerful backbone, replacing classical networks based on CAN or ProfiBUS. In particular aspects of synchronisation and real-time-processing in combination with the compact data packaging are interesting for measurement applications with a big number of distributed analog channels. E.g. in applications where torque and speed of rotating parts are picked up just to measure, to detect or even to prevent oscillations, it is very important to synchronize the sampling of data at the distributed converter modules. Only this allows then to calculate exact phase information from the measured signals and evaluate and prepare the data according to the requirements of an application on top.
Although EtherCAT supports a big number of distributed devices and is known to handle about thousand digital channels in cycle rates of up to 10 kHz, it does not make sense to feed all measurement data into the context of an automation system. Usually the controlling parts of automation systems are interested and focused on real-time-signals without respect to histories. Feedback-Controllers have to use the latest values from the process to provide as quickly as possible control values to actuators. Digital information is processed in Soft-PLC modules, to provide fast reactions on certain events. However, measured signals needs different handling of the data stream. Not only filtering but also the calculation of characteristic process coefficients and real-time logging of measured signals is not a typical task for automation systems. They should receive only a subset, some few characteristics or at least reduced data streams for supervision and visualisation. This paper shows an approach to use the capabilities of EtherCAT in structured network segments, combined with multiple master/slave functionalities to fulfill the special requirements in measurement applications.