With
openSAFETY,
the Ethernet POWERLINK Standardization Group (EPSG) believes it has laid the
foundation for the first completely open, safety-related data communication
protocol for all areas of automation.
With communication cycles in the microsecond
range, the TUV Rhineland certified protocol guarantees fast response times and a
high level of machine safety suitable for use in systems rated up to SIL 3.
"The key with openSAFETY is that it offers an
open safety solution," says Robert Muehlfellner, automation director for
B&R Industrial Automation. "When you look at the systems for safety in the
marketplace, implementations are normally specific to manufacturers and the
communications system that is behind it."
"Whether it is CIP Safety over EtherNet/IP or
PROFIsafe over Profinet, the major manufacturers are driving safety standards within
their systems. The idea behind openSAFETY is something that goes beyond what is
available on the market today, and to set a trend for future interoperability
of safety systems," he says.
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Because openSAFETY is bus
independent, it can be used with all fieldbus systems or industrial Ethernet
systems. In order to demonstrate the interoperability of the safety solution
with different protocols, the EPSG presented four different openSAFETY
solutions at the 2010 Hanover
trade show, which were created using the most common implemented industrial
Ethernet protocols: SERCOS III, Modbus TCP, EtherNet/IP and Ethernet POWERLINK.
The potential benefits of openSAFETY
impact three specific groups: manufacturers of safety devices, OEM machine
builders and end users. For device manufacturers, a key benefit is doing an
implementation only once. Today a light curtain, e-stop or other safety device
needs to be hardwired to a safety I/O module instead of directly connecting to
a particular network.
Because there is significant implementation
to make a PROFIsafe version of the device, a CIP Safety version and so on,
openSAFETY means vendors could implement the device once and automatically
connect with the different networks.
The main benefit for an OEM is an
open safety protocol where they are no longer forced into using a particular
control to satisfy end user demands for interoperability between machines in
the production line. OEMs are already moving away from hard-wired solutions to
integrated and programmable safety. OEMs can select systems without being
restricted on using a particular brand to tie safety systems together.
For end users, it offers a standard
for adding integrated safety systems across their entire plant floor. Today,
users might have individual machines with individual safety systems, and some
hardware handshaking to communicate between them. Or as end users right now
demand that you need to use Brand X because it is the only way to tie safety
systems together, users can now have those supervisory safety standards and
systems communicate across different communications platforms from different
controllers by using an open safety standard.
"OpenSAFETY is primarily a software
innovation, and part of the key is the basic telegram format that the system
uses," says Muehlfellner. "The system uses a black channel principle which
means that all of the information is verified, to achieve the basic goal with
safety systems which is avoidance of undetected errors."
He says what makes openSAFETY unique is that
all of the redundancy checks are done within the software itself, and it is
achieved independently of the actual transportation layer. Whether the system
is implemented on an EtherNet/IP, Modbus, SERCOS or Ethernet Powerlink network,
the proof of concept has shown that it can be implemented on any type of
communications network because the system is totally hardware independent.
The protocol itself is certified and open to
companies to integrate hardware devices that can operate using the protocol
from light curtains, to safety I/O modules, to drives and programmable safety
controllers. Today many of these safety devices are still hard-wired into safe
I/O modules and programmable safety systems, and devices do not sit directly on
the bus.
"So
far, the standard has been finalized for anyone to implement," says Muehlfellner.
"We have done a proof of concept and shown we can have a B&R processor and
safety I/O running underneath a Rockwell system on an EtherNet/IP network."
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