By Joe Feeley, Editor in Chief
WE'VE INVESTED A FAIR amount of space this month in Ethernet, both wireless and wired species, particularly those wire-based hybrids in which the DNA of the telegram-handling scheme has been altered to provide more possibilities for real-time response.
Wayne Labs contributes an expansive cover story, beginning on page 14, which attempts to sort out the fundamental differences among those real-time Ethernet flavors that compete for your real-time control soul.
The major takeaway from his piece should be a better grasp on the differences among these networks, so, in concert with your comfort level of the vendor support each brings to the factory floor, you can sift out the marketing verbiage and learn how it fits your application.
Part II of the ambitious study of wired and wireless Industrial Ethernet use conducted by Venture Development, participants in which included Industrial Networking subscribers, is on page 21. From a vast amount of data, we’ve passed on results that detail a wide variety of wireless technology use, device density, and expectations about the increased use of battery-powered devices and emerging Power Over Ethernet (PoE) capability.
As it happens, a copy of Dick Caro’s new (downloadable from isa.org’s book page) digibook, Wireless Networks for Industrial Automation, came across my desk while we were building this issue. Caro has a long, involved, and adventurous history with industrial networks, in particular the tumultuous, briefly optimistic times when the concept of a unified fieldbus standard underestimated the politics that would ultimately gut it. His research and thoughts about industrial networking carry some weight, as a result.
I want to mention a couple of things he says, as ballast for the generalized optimism about the inevitable, unbridled embrace of wireless industrial networking. “The expectation is that the manufacturing industries will soon adopt wireless technology,” Caro writes. “This is not the case. Industry expects more than does the small or home office...wireless on the factory floor will cost much more to provide the reliability and performance all industrial processes demand.”
Part of that viewpoint comes from the embedded quality problems of wireless. Caro points out one of the more frustrating issues. “Wireless networks still suffer from mysterious dead spots, and sometimes live spots just move or, in the language of radio, fade,” reminds Caro. “The spontaneous loss of communications for no apparent reason is probably one of the most irritating aspects of wireless.” Maybe worse, adds Caro, the signal often returns before the cause of the loss can be looked into. That does pretty much fail the reliability test, don’t you think?
The author is, however, optimistic about wireless technology for industrial automation. “The real payoff from wireless will come when field devices having standardized wireless connections are available,” he writes. “Although there are suppliers attempting to establish de facto standards for their devices, there are too many variables for standardized wireless connections to become a reality soon.” The issues that our survey respondents raise are those very ones that Caro IDs as needing resolution.
The issues, political as well as technical, have to be solved by standards groups, not by individual suppliers, and Caro endorses the Wireless Industrial Networking Alliance (WINA) as an organization well-suited to address them.
If you’re determined to step into wireless now, Caro recommends trying it “where one of the Ethernet-based networks such as Foundation HSE, EtherNet/IP, Modbus/TCP or Profinet can be used.” He says be prepared to do a lot of planning to design a setup where all nodes are clearly in range of today’s wireless access points. “The investment should be made in only Wireless A/B/G devices of commercial grade, not the less-expensive home grade.” And, don’t forget those dead spots.
By Joe Feeley, Editor in Chief