Traditional networks go together easily because everyone understands them. If you’re considering installing a modern network, you may want to consider this: Who will maintain it?
“I have a network with 58 workstations and four servers,” reports [[NAME???]] a control engineer at a chemical manufacturer [[NAME??]] in N.J. “The workstations are located in the various control rooms. Because of downsizing, I’ve been waiting for corporate support for more than six months, since we identified some significant networking problems. Prior to this, I waited for almost a year for the technical support to identify the problems.”
If you too rely on your IT department, you may run into the same situation. “Our technical experts, who’ve spent most of their careers installing office networks, assume that an occasional re-boot to clear an error is acceptable,” he says.
While keeping in mind that emerging technological edges can be sharp, maybe even dangerous, let’s look at trends in industrial networks (See Figure 1 below).
FIGURE 1: HIERARCHY OF INDUSTRIAL CONTROL NETWORKS
UP FROM THE ASHES
One way to gauge the success of a technology is to note how many new products use it. While every product now comes with an Ethernet port, many also come with a Modbus port. Similar to the legendary phoenix, Modbus is rising from the ashes of the destruction that killed off many other networks that first saw light in the 1970s.
Why would a clunky network from the Dark Ages of control remain so popular? Bryan Moore, product manager at ABB
, says Modbus probably will be around forever. “It doesn’t require special electronics, any PC or PLC can run it at the serial port, it’s very low cost, and it supports 256 stations,” says Moore. “That’s a lot, compared to a DeviceNet or Profibus network.”
Yes, it’s slow. “But that means it can cover long distances,” Moore explains.
Yes, it’s rudimentary. But it has become a “least common denominator,” adds Moore, like the RS-232/serial ASCII connections of the past. “You can always interface to it. Chances are, if you have any old control equipment or instrumentation in the plant, it probably has a Modbus interface.” WHAT ABOUT WIRELESS?
Jumping from one of the oldest network technologies to the newest, let’s look at wireless. Although some users are wary of wireless, it has taken center stage in the industrial networking theater. Sales are still at entry levels for a new technology (about $75 million in 2003), but market researchers predict good times ahead.Venture Development
says the market will grow about 35% annually, reaching $183 million in 2006. Frost & Sullivan
projects that wireless sales will quadruple by 2006. A recent IDG
. World Expo report goes even further, predicting that the wireless sensing technologies market (including sensors) will be greater than $10 billion by 2010.
Many big vendors are jumping on the wireless wagon. The HART Communication Foundation
is adding wireless capability to its HART devices, and all the major control vendors are keeping an eye on what wireless is going to mean to process control and automation.
Gene Chen, product manager at Honeywell
says that Honeywell is an executive sponsor of the three main bodies trying to define a wireless industrial standard. These include the Wireless Industrial Networking Alliance (WINA), ISA SP100, and ZigBee, a consortium of component-level OEMs. Gene Sierra, wireless marketing manager at Emerson Process Management
, says that Emerson is working with HART and ISA.
Hesh Kagan, director of new technology marketing at Invensys Process Systems
, says motes (wireless nodes) and mesh networks are coming. “At the low end, wireless sensors use mesh networking with auto-adaptive, self-healing capabilities,” says Kagan. “Companies such as Millennial Net and Ember are driving standards-based end nodes, radios on a chip, mesh-networking software, gateways and development environments.”
Venture Development says its data agrees. It reports that mesh networks will grow from a miniscule $6 million in 2004 to $25 million in 2007, a growth rate of 60%.
Kagan sees tremendous opportunities for wireless sensors in process applications. “Most process plants today take measurements at only about 10% of the possible points. But if the attachment and sensor costs were low enough, as mote technology promises, you could measure at many more points, giving you a much richer process model with which to work.”
The biggest issue in wireless appears to be the lack of a universal standard. Three groups are working on it: WINA, ISA and ZigBee. “Not having a single backbone slows down adoption,” says Honeywell’s Chen. “Several cases exist where customers spent resources to deploy wireless networks to support tablet PCs for operators, but found the network wouldn’t support wireless sensors. Other customers had the opposite problem when they installed wireless sensors.”
According to Venture Development analyst Jake Millete, ZigBee looks promising, but vendors are sticking to their proprietary methods. “Many vendors feel ZigBee is an excellent solution for a variety of applications,” notes Millete, “but for industrial applications where a robust network is essential, some develop their own mesh networks. We’ll see many more ZigBee-based solutions in the industrial market as the standard matures.”