Posted to News on 24th Apr 2008, 16:43
A safe, real-time Ethernet protocol - SafetyNET p
Stewart Robinson of Pilz Automation Technology outlines the technology underlying SafetyNET p, a safe real-time industrial Ethernet protocol.
Current automation technology requirements are reaching the limits of the industrial fieldbus systems that are currently popular. The time is therefore right for suppliers to provide new fieldbus systems that offer significantly improved features.
Automation technology is moving away from centralised control systems with simple, bit-oriented sensors and actuators; the trend is towards distributed systems with more sophisticated sensors and actuators that incorporate an ever-increasing amount of onboard pre-processing. The communication requirements of systems are consequently moving away from the currently common master-slave bit transfer arrangement to networks capable of transferring commands and requests between intelligent master systems.
Ethernet is a central, widely available and well known communication medium that is capable of being used for complex systems at reasonable prices. If automation technology takes advantage of Ethernet, the potential for innovation is enormous. However, there is a need to simplify Ethernet installation and configuration, as current commercial-grade Ethernet systems are still quite complex and difficult to work with compared to industrial fieldbus systems.
Machine productivity requirements are driving a reduction in machine cycle times. Automated system performance must therefore be sufficient to cater for such reduced cycle times, which, in turn, requires modern fieldbus systems to be capable of realising significantly shorter cycle times than current systems can provide.
SafetyNET p is a modern Ethernet-based industrial fieldbus system that has been developed in response to the new challenges in automation technology. It satisfies users' requirements while still being as easy to install as the currently available industrial fieldbus systems.
Two versions
In order to meet the various industrial requirements, SafetyNET p supports two types of communication. The SafetyNET p RTFL format is optimised for extremely fast communication in highly dynamic applications. The RTFN format also provides the ability to communicate via any Ethernet network. Both versions are compatible with each other and may be used separately or in combination.
SafetyNET p demonstrates that it is possible to meet the user requirements of an open, safe and deterministic real-time Ethernet network. The real-time performance, with scan times of 62.5us for the RTFL version, is around 20 times faster than most other industrial Ethernet versions. It is open for any type of Ethernet traffic, even for data traffic from other industrial Ethernet versions.
Extremely versatile connection technology enables a SafetyNET p network to have a linear, tree or star structure. The capability for structures and subscribers to be changed during operation is unrivalled.
To ensure that the system is open and widely propagated, integration is being supported by Safety Network International eV. This organisation offers its affiliated member companies product-neutral integration utilities and development support.
For more information about SafetyNET p visit www.pilz.co.uk.
