Often, information is gathered to determine when routine maintenance should be performed. Diagnostic data also helps tell operators and managers how efficiently their production lines are flowing.
As managers strive to improve efficiency and reduce downtime, the ability to gather more diagnostic data without impacting production becomes increasingly important. The speed and high bandwidth of Ethernet makes it possible to collect data while still delivering all the instructions needed to keep equipment running. That’s a major improvement over slower fieldbuses.
“One of the things that comes with Ethernet buses is high throughput, which lets you transmit a lot of diagnostic data,” Stephan Stricker, product manager at B&R Industrial Automation Corp., an Austrian automation supplier with U.S. headquarters in Roswell, Ga., says. “With most fieldbuses, you can’t get much diagnostic data because the bandwidth is taken up by user data.”
The ability to move lots of data over Ethernet makes it possible to collect data from every connected point on a machine.
“With EtherNet/IP, you can see exactly what’s happening with a device, getting up to 500 parameters that can all be sent to the controller. Ethernet packet sizes are larger than packets in many industrial architectures, so you can send more data,” says Brian Oulton, networks business director at supplier Rockwell Automation Inc., in Mayfield Heights, Ohio. EtherNet/IP is an ODVA specification that blends the network with industrial protocols.
Though Ethernet provides far more bandwidth than older fieldbuses, there are still applications for which additional speed is needed. Most input/output (I/O) devices don’t send or receive huge files, so conventional Ethernet links provide more than enough bandwidth.
But when large facilities with many complex machines consolidate on a single networking architecture, the need for speed increases. Developers of the CC-Link network are finishing up a high-speed version that focuses on fieldbus applications.
“CC-Link IE FieldNet will bring the Gigabit speeds of Ethernet down to the device level,” says Chuck Lukasik, director of the CC-Link Partner Association, in Vernon Hills, Ill. “That’s 10 times faster than the 100 Megabits competing Ethernet networks are running at now. When you’ve got hundreds of thousands of devices on your network, you need that speed.”
That speed will help technicians because more diagnostic data can be sent, making it easier to move from diagnostics to prognostics. “The system can routinely monitor something like pressure for a particular field device,” Lukasik says. “At any given time, a controller can access that data and see if the trends predict a failure.”
Working in real time
When users want more bandwidth and determinism than they get with conventional industrialized versions of Ethernet, they have a number of real-time options. Combining Ethernet’s connectivity with determinism and increased bandwidth also adds more capability to examine every aspect of a machine. There’s a wealth of data available when design engineers extend Ethernet down to individual sensors and actuators in real-time equipment.
“With EtherCat, you have diagnostics right down to the I/O level. You can examine hundreds of I/O points,” says Joey Stubbs, North American Representative for the EtherCat Technology Group. Its U.S. headquarters is in Volente, Texas. “Your scan rate can be higher so you don’t need separate networks for high and low speeds.”
Real-time versions of Ethernet offer enough speed to send detailed diagnostics even when the network is carrying complex control communications such as motion. The Sercos motion control interface now communicates over Ethernet links, providing enough bandwidth to closely examine these demanding systems while they’re running.
The ability to access diagnostics without causing a glitch is an important trait in any network. But in the complicated world of motion control, gathering data while high-speed actuators are in action is even more difficult.
“If you alter the timing in a network, you can create a fault,” says Kurt Wadowick, I/O Systems Product Specialist for Beckhoff New Automation Technology, of Burnsville, Minn. “With Ethernet, you’ve got enough bandwidth to get complex images without hampering performance.
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