23/10/06 - Article - AS-Interface Safety at Work: A Safe Quantum Leap




AS-Interface Safety at Work

A Safe Quantum Leap


Typical AS-Interface: As soon as an innovation begins to become the norm, the next drum roll can't be far off. After a swift start as a ground-breaking development in safety technology, the Safety at Work concept has become fully estab- lished: There are now more than 170,000 installed AS-i capable safety components. Which makes it just the right time to present the next stage of evolution: decentral AS-i Safety Outputs.


There seems to be no record of whom film directing legend Billy Wilder directed the following words to, nor do we know that person's response. "The script is absolutely perfect", the multiple Oscar winner is alleged to have said to one of his authors. "And now we'll make it better."

In any case, this bonmot applies perfectly to the dramaturgy of the AS-Interface Safety at Work success story. No other system has changed safety technology in automated manufacturing so fundamentally over the past few years. Safety at Work still represents the only approach to sending safe and non-safe signals over the same cable – namely the simple, yellow AS-i cable.

At first met almost with disbelief even by experts, the system has quickly established itself on a broad basis: There are now more than 170,000 AS-i capable safety components in use. And while this innovation increasingly becomes the norm, the next evolutionary stage is already taking concrete form.



Evolution follows revolution: Safety at Work with decentral AS-i Safety Outputs

The vision of direct, safe switching of actuators using the Safety Monitor has existed of course since the system was first introduced. Step by step the AS-i Safety Outputs project rose higher on the agenda of the developers, and in December 2005 the last hurdles were cleared with concept approval from TÜV: The AS-i specialists at Bihl+Wiedemann were given the go-ahead by the Safety Consortium of the manufacturer's association to create a reference implementation of the AS-i Safety Outputs.

One of the critical advantages of the new technology is the decentralizing of safety switching circuits. As opposed to the previous approach with Safety Outputs contained in the Safety Monitor, which safely turned the system off in case of a problem, the new Safety Monitor can now control and safety switch the AS-i Safety Outputs of actuators directly through the yellow cable. As before, the actuators are assigned a standard address for operation-specific switching. In addition, the switching signal is enabled by the Monitor via a safe address, to which the AS-i Safety Output then responds. Safe signals can also be sent for selecting parameter sets in sensors.

It's a safe bet that with this new system AS-Interface has opened a new chapter in the success story of Safety at Work. The expansion of logical capabilities promises not only more convenience together with further cost reduction for the AS-i customer, but also opens up a variety of new application opportunities for the entire concept.



Even more logic-even more possibilities: The expanded functionality makes AS-i Safety at Work ideal for new areas of application

A simple example can illustrate some of the options this innovation creates in practice: If the user not only needs the Safety Outputs on the monitor but also requires the safety output signal at a different location in the system, he can now forego the installation of an additional Monitor. Instead he simply uses an AS-I Safety Output which is switched and supplied with secure output information by the central Monitor through the yellow cable. As with all slaves, only the AS-i address needs to be set on the AS-i Safety Output.

This new functionality also makes Safety at Work even more interesting for safety-relevant applications in drive technology, such as when valves need to be safely turned off, be it in active braking systems, smoke evacuation flaps or Control Category 4 safety valves.

That Bihl+Wiedemann, as one of the youngest members of the Safety at Work Consortium of AS-International, received the development contract for reference implementation of the new technology was first met by the Mannheim firm with mixed feelings: "On the one hand it's rather like being knighted – but at the same time it is an enormous responsibility." But when the Safe AS-i Outputs showed live in a demo application what they were capable of, the tension changed to knowing enthusiasm in a matter of seconds: "One small step for AS-i – one giant leap for safety technology."



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