fieldbus wars may be over, but the new battleground in machine and motion
control networking is now centered on industrial Ethernet and competing
networking protocols and standards. The good news is that industrial networks
are growing in popularity and sophistication and are offering new application
solutions targeting energy savings, safety, enhanced network performance and
better overall machine control.
industrial networks, we're at a point where we have stability in fieldbuses,
and Ethernet-based networking, such as EtherNet/IP, is where we're seeing
technology advances," says Richard Harwell, manager of connectivity for Eaton
Corp. and chief technology officer for ODVA.
says that throughout ODVA's history with Ethernet development, the emphasis has
been on the use of standard, unmodified Ethernet. What that provides is an
ability to ride the technology trends and the fundamental networking advances
that come with Ethernet. The performance of the one gigabit standard and
wireless technologies in many different flavors and forms are prime examples.
In addition, Ethernet infrastructure devices such as routers and switches are
increasingly adding capabilities. More web enabled devices including 3G and 4G
phones are providing capabilities that spill over into the industrial
is also focusing on fully introducing new capabilities such as the Device Level
Ring (DLR), which addresses particular issues with applying standard Ethernet
in the industrial environment. If you look at standard Ethernet topologies,
such as rapid spanning tree, network healing times are measured in hundreds of
milliseconds to several seconds, which is just not fast enough for industrial
applications. Device Level Ring provides healing times measured in
control is an especially suitable area for DLR technology application,
especially motor control centers or a line of servo drives with multiple
devices connected in a straight line. In both cases, DLR may be the difference
between Ethernet being an applicable network technology or not, as such a
topology requiring long runs of Ethernet cabling is not always practical. For
example, DLR offers distinct advantages via multiple ring topology options if
you have a machining line with 20 devices that runs several hundred feet.
and Wireless Data Access
is an established technology for machine level control networks. Currently, the
EtherCat Technology Group (ETG) is focusing on the factory network by enhancing
the specification and defining services for the supervisory control level. The
new EtherCAT Automation Protocol (EAP) reportedly simplifies direct access of
process data from field devices at the sensor and actuator level, and also
supports the integration of wireless devices.
provides technology and using EtherCAT as the network communication level for
controller-to-controller or master-to-master communications," says Joey Stubbs,
North American representative for the EtherCat Technology Group. "It operates
independent of the type and speed of Ethernet used and can be routed over
wireless networks to specifically target the process control level."
though it provides PC-to-PC or master-to-master communications, but not the
fieldbus level, it uses the same protocol and enables passing data from one
EtherCAT network to another. EAP can also be used by an enterprise system to
configure low level devices in the field.
is an important issue for applications not well-suited for the Fieldbus device
level because of the amount of data they need to communicate," says Stubbs. "It
is ideal for applications such as vision where you have very large frames of
example, a camera can use EAP to move the vision data, but then the EtherCat
Device protocol (EDP) via traditional EtherCat fieldbus controls the process
and triggers events based on what the camera sees.
Click here for larger image
says EAP uses the same EtherCAT protocol, but allows users to move data in a
non-deterministic format through the Internet or across an enterprise network.
It fills the gap for controller-to-controller communications, and how to
communicate large chunks of data between PLCs or controllers on the factory
floor. It is implemented as a separate network and physical wiring using a
different port on the computer or PLC but, because it uses the same protocol,
process data from a device can be encapsulated and moved up for
diagnostic and configuration interfaces are also part of EAP, and it can be
used in switch-based Ethernet topologies as well as wireless Ethernet. Process
data is communicated like network variables, either cyclically or event-driven.
Both the classic EtherCAT Device Protocol, which utilizes the special EtherCAT
functional principle of "processing on the fly," and the new EAP make
use of the same data structures and facilitate vertical integration to
supervisory control systems and networked controllers.
is a new applications profile that sits on top of the PROFINET
communications protocol without impacting it from a performance standpoint. Its
primary goal is to provide a way for users to conserve energy during production
pauses, especially in discrete manufacturing automation applications. It was
instigated by a study of energy use at automotive companies that shows that
even when a machine is not producing product, it is still using 60 percent of
the energy required to run the machine.
PROFIenergy, energy use during idle times can be reduced from 60 percent to 20
percent," says Carl Henning, deputy director for the PROFINET Trade
automotive companies came to us early in 2009 wanting a multi-vendor solution
because they had adopted PROFINET and wanted us to build on that capability."
cases focus on the fundamentals of saving energy during production pauses, idle
machine time, long and short pauses, lunch breaks or weekends. Other uses
involve moving into a power saving mode if there is an unplanned shutdown, and
monitoring energy usage to identify and take action to prevent peak energy
bills for industry typically have two components: both a usage and peak demand
component," says Henning. "If you can shave off the peak demand, users can save
some applications, there are auxiliary processes not directly tied to
production that can be slowed down or stopped, and may provide an opportunity
to shave off the peak demand.
could achieve these same energy savings goals but would need to install an
electromechanical contactor ahead of a conveyor, for example, and then write
custom logic in a PLC to control when to shut it off the machine including
specifying parameters for how long it takes to shut down and start-up the
machine, and if the shutdown needs to be for a certain period of time. With
PROFIenergy, users create a function block in the PLC and then give the
manufacturer of the device ability to put in parameters such as how long it
takes to shutdown, connect and so on. Those parameters are used in the PLC
logic rather than custom programming.
III was introduced in 2005, effort has been poured into making it a complete
automation network solution. All versions of SERCOS are designed to ensure a
reliable, isochronous and extremely fast real-time communication, which is the
basis for interoperability at the application level. The latest version of the
SERCOS III specification is expected to be released in the third quarter of
2010 and include several new profiles and enhancements including extensions to
the drive profile to support hydraulics and pneumatics devices, extensions to
the I/O profile for enhanced diagnostics and additions to the communications
profile to support new features such as oversampling and time stamping.
new SERCOS Energy profile emphasizes reduced energy usage and conservation for
controls, drives and decentralized peripherals. One target is to reduce the
permanent load at motor/machine standstill, and dynamically adjust energy
consumption depending on the process by considering the target completion
times/dates (partial load operation). Another target is switching off
components during processing that are not required at a particular time or
point in the process.
and conformance testing is a final area of continued emphasis for the SERCOS
group. In fact, efforts to achieve truly interoperable systems are what's "new"
with many of the extensions.
Hibbard, vice president of technology for Bosch Rexroth Corporation, says that
interoperability is the challenge in deploying these types of systems because
of the complexity of highly coordinated, synchronized motion applications.
think that the world is really starting to embrace the whole idea of
distributed control," Hibbard says. "Where you put intelligence down at the low
levels, if it is just a dumb drive, there is only so much you can standardize.
But if it's an intelligent drive or a pneumatic valve with diagnostics providing
life cycle or pressure information, the smarter you make the peripherals the
better definition you have to provide if you are going to make them
interoperable. That's why you see a lot of that work going on, both more
communications and more intelligent communications on the network."