Industrial Ethernet Applications Expand

The 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.

"With 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.

Harwell 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 networking world.

Multiple Topologies

ODVA 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 milliseconds.

Motor 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.

Wired and Wireless Data Access

EtherCAT 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.

"EAP 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."

Even 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.

"This 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 data."

For 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

Stubbs 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 controller-to-controller communication.

Uniform 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.

Energy Management

PROFIenergy 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.

"Using PROFIenergy, energy use during idle times can be reduced from 60 percent to 20 percent," says Carl Henning, deputy director for the PROFINET Trade Organization.

"The 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."

Use 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 usage.

"Utility 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 significant dollars."

In 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.

Users 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.

Embracing Distributed Intelligence

Since SERCOS 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.

A 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.

Interoperability 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.

Scott 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.

"I 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."