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PACs Gain Momentum

While not everyone likes the name, a new generation of programmable automation controllers that feature multi-domain control functionality are helping to reduce costs for a growing number of manufacturers.

The deepest penetration of PACs to date has come in high-end applications requiring more than 500 input/output (I/O) points, say
The deepest penetration of PACs to date has come in high-end applications requiring more than 500 input/output (I/O) points, say

PAC—it’s one of those analyst-generated acronyms that seems to have stuck, though it’s a term that continues to cause confusion in some circles, as well as consternation in some vendor camps. It was late 2002 when Craig Resnick, a research director at ARC Advisory Group Inc., first published the term PAC—for programmable automation controller—in an “ARC Insights” document sent to clients. ARC, based in Dedham, Mass., coined the PAC term to describe a new class of open, multi-functional, integrated control systems that was emerging within the controls space occupied by that most venerable of automation workhorses—the programmable logic controller, or PLC.

“The PLC is very much alive and well, with a long life ahead,” Resnick assured readers in that “ARC Insights,” dated Nov. 20, 2002. But the document went on to observe that “the label ‘PLC’ simply understates the capability of current automation systems. As a new generation of functional capabilities pervades the market, the more apt notion of Programmable Automation Controllers (PAC) will displace its [PLC] predecessor,” Resnick predicted.

Growing fast
Today, more than five years later, PACs so far haven’t come close to “displacing” PLCs. According to a 2007 ARC study, the worldwide market for PLCs totaled $8.3 billion in 2006, and ARC projects compound annual growth rates at 7.3 percent for the category through 2011, when PLC sales will total nearly $12 billion.

PACs, meanwhile, are currently deployed in only about 5 percent of the applications that could potentially benefit from their use, Resnick estimates. But PAC sales are growing significantly faster than those of PLCs, he says. Though ARC hasn’t done a formal study on the topic, Resnick ventures that PAC sales growth lately has been running at 15 percent to 20 percent annually, and the total PAC market last year was probably “well north of a billion dollars. We have a long ways to go,” Resnick allows. “But I can tell you that sales [of PACs] continue to be very, very strong.”

The PAC terminology has so far been unevenly embraced by control systems vendors. Some have questioned the need for another industry acronym. But other suppliers were quick to begin using the name, as a way to help differentiate their products. And many contend that they were well ahead of the game in offering expanded, PAC-like controller capabilities before ARC came up with the name.

“What the PAC name did for us was to give us a way to identify what we were already doing, because people tended to lump [our product] in with PLCs, and in a number of ways, it’s dramatically different,” says Tom Edwards, senior technical advisor at Opto 22, a Temecula, Calif., vendor, speaking of his company’s Snap PAC family of controllers.
At Rockwell Automation Inc., the Milwaukee-based PLC and controls systems heavyweight, Ken Deken, vice president,
portfolio management, declares that his company’s ControlLogix platform, introduced in 1998, “from day-one has been a programmable automation controller.”

And at GE Fanuc Intelligent Platforms, the Charlottesville, Va.-based automation supplier, Controllers Business Manager Connie Chick recalls that when ARC’s Resnick first began talking about something called “PACs,” her company was already “in design phase” on a new controller line that met the PAC definition. The company recruited Resnick to help introduce the line—called the PACSystems RX7i—at road shows and Webinars in mid-2003, Chick relates.

Only in America

 Still, other controls vendors have remained standoffish about the PAC name—in part, perhaps, due to its U.S. market origins.

France-based Schneider Electric, whose Modicon brand traces its roots all the way to the 1968 invention of PLCs, did not introduce its first product dubbed a PAC—the mid-range M340—until June of last year, even though earlier Schneider products have offered PAC-like characteristics. That’s because customers until now have been generally happy with the PLC name, say executives at the company’s North American operations, in Palatine, Ill.

And in fact, the Schneider move to the new name is only happening here. “In North America, Schneider Electric is referring to the Modicon M340 as a PAC, because we want our North American customers to know that the M340 has the capabilities that this market associates with a PAC,” says Geoff Walker, director of strategic accounts for the Schneider Electric North American Operating Division. But because the European market “has not put much emphasis on PACs vs. PLCs,” says Walker, the company still uses the term PLC in Europe when referring to the Modicon M340.
At Siemens Energy & Automation Inc., another big automation controls vendor whose parent is based in Germany, Bob Nelson, business manager for controller, I/O and engineering software products, based in Norcross, Ga., is adamant that his company has no plans to adopt the PAC name.

“If you want to come up with a new acronym in what is already an acronym-rich industry, that’s fine,” he says. But the functionality that ARC first attributed to PACs in 2002 has long been available in Siemens’ S7 controller family, first introduced in the mid-1990s, Nelson notes, and Siemens sees no need to “confuse” customers by changing the name now.

"I personally am a little bit frustrated,” says Nelson, citing the growing industry use of the PAC term and references to “PAC-like” functionality. “I hope it doesn’t get to the point where a customer says, ‘I’ll only accept a PAC—no substitutes,’ ” he declares. “Because if you don’t happen to apply that acronym to your product, but your product can do functionally all of the requirements that the customer is looking for, isn’t that more important than the acronym that you apply to the product?”

What is it?

So what the heck is a PAC anyway, and what makes it so great?

One key characteristic of a PAC is that it is a multi-domain platform, says Resnick. Unlike traditional PLCs, which were limited to sequential logic solving, PACs can perform other functions as well, such as motion control and process control, all on the same controller platform. Further, a PAC relies on a single, multi-discipline, integrated development environment that uses common tags and the same database for all functions.

This means, among other things, that a single human-machine interface (HMI) can be enabled for all functions. “You’re not required to separately look at a motion controller, or separately look at a process controller or the logic controller,” Resnick observes. “You’re able to view all the disciplines on a single screen, if that’s the way it’s configured.”
This multi-domain capability also greatly reduces total cost of ownership, says Resnick, by reducing the time needed for design, programming and engineering, while also lowering installation, start-up, training, spare parts and maintenance costs.

GE Fanuc’s Chick agrees. With a PAC, she says, “you’re reducing your costs in about five different ways, and your system is probably faster because you don’t have to connect up to all these different things, using different communications.” Compared to an approach based on separate multiple controllers for varying functions, “our [PAC] customers tell us they’re saving from 25 percent to 40 percent overall,” Chick says.

Resnick estimates that up to half of all applications using large PLCs today could potentially benefit from the multi-domain capabilities of a PAC. And a growing number of end-users are making the transition, he says. The automotive industry is moving to integrate robot control capabilities into their automation control platforms, for example. PACs are also moving strongly into so-called “hybrid” applications in industries such as food and beverage, and pharmaceutical, says Resnick. In many of these applications, a single PAC can handle the process control required during the production of a product, as well as the logic and motion control needed for handling and packaging the product.

Besides multi-functional control capabilities, additional key requirements for any PAC include open, modular architectures, and compliance with de facto industry standards, Resnick notes. This extends to the use of standard programming languages, such as those based on the International Electrotechnical Commission’s IEC 61131-3. And it includes compliance with communication, networking and interoperability standards, ranging from Ethernet and its various industrial flavors, to XML (for eXtensible Markup Language) and OPC, an open communication standard.
With PACs, “we are thinking of something that gives users peace of mind that they are not buying an island,” Resnick explains. “They’re buying something that has the capability to interact with other automation equipment, and even has the ability to take all the data that it’s picking up from the factory floor and send it up to the production management space.”

“A PAC is a communication-centric device,” agrees Opto 22’s Edwards. “We communicate point-to-point with Ethernet, but moreover, with the rest of the enterprise,” he says of Opto’s Snap PAC product line. “We have the ability to read and write from a number of different databases, any place on a local area network, or even across the Internet.”

Players and markets

 Unlike the PAC offerings from major vendors with a PLC heritage, says Edwards, Opto’s Snap PAC architecture is based on a ruggedized, general purpose computer platform with strong communication capabilities, which is combined with intelligent, distributed input/output (I/O). This architecture works well in industries such as water/wastewater, for example, where a need for radio communications with remote lift stations and pumps is common. The Snap PAC has also done well in the semiconductor industry, because of its ability to deal with a mix of analog and digital I/O, Edwards adds, as well as in oil and gas, where “we do plenty of analog processing at the I/O level.”

Another non-traditional-PLC vendor that plays in the PAC space is National Instruments (NI), Austin, Texas, whose roots are in testing and high-speed data acquisition. NI’s CompactRio PAC platform not only merges many of the features of industrially oriented PLCs together with the improved communications and other features associated with personal computers (PCs), but it also adds a custom capability based on field programmable gate array (FPGA) integrated circuit technology, says Todd Walter, NI market development manager. “This means that customers can add in their own custom high-speed digital triggering, high-speed signal processing, high-speed control capabilities and machine condition monitoring, all mixed in the same platform.”

As a result, says Walter, end-users often choose NI’s PAC solutions to meet special challenges. One maker of steel rolling mills selected the CompactRio to replace a PLC that wasn’t fast enough to handle the high-speed feedback from a specialized analog sensor used to control rolled steel thickness, for example. “Most of our customers are saying, ‘Hey, I’ve got a very difficult control automation challenge, and your PACs have the sophisticated analysis and algorithms to handle that,’ ” Walter relates. “We run into fewer customers who say, ‘Hey, we’re setting up a whole manufacturing system, so your tie-in to the MES (manufacturing execution system) is the most important thing.’ ”

High-end leverage

 Among the traditional mainstream PLC providers, Rockwell Automation, for one, says that a major part of its PAC business does involve communication with higher-level systems, as well as factory-level control integration. “The primary area where we’ve seen acceleration [in PAC deployment] is in the large controller space of 500 plus I/O points, and, more specifically, in industries where the multi-discipline and plant-wide control concepts of PACs can be leveraged,” says Frank Kulaszewicz, vice president and general manager for Rockwell’s Logix/NetLinx business, in Mayfield Heights, Ohio. One area where this trend is apparent, for example, is in regulated industries, such as pharmaceuticals, Kulaszewicz adds.

In the years since ARC coined the PAC name, Rockwell has made numerous additions to its Logix PAC family, says Deken. The company’s GuardLogix technology added integrated safety to the multi-discipline mix of discrete, process and motion control technologies that can be handled on a single platform, he notes. And Rockwell has also made numerous enhancements around information flow, Deken adds. “For example, we now have embedded alarm and event server capability in the controller, and we’re making much greater use of Web Services for interface with the MES layer.” Other advances include new capabilities around user-defined instructions in templates, which allow customers to create reusable blocks of code that include HMI code as well as control code.

In all, Logix family PACs now account for perhaps 60 percent of Rockwell Automation’s controller sales, Deken estimates, though that figure is closer to 90 percent at the high-end of the line for ControlLogix systems with more than 500 I/O. Rockwell now sees potential for accelerating growth for PACs in the mid-range control space involving 100 to 500 I/O, says Deken, “because some of those higher-end features have migrated down into the mid-range and lower-cost platforms.”

GE Fanuc’s Chick sees the same kinds of trends. “PACs have initially been used in the mid- to high-end, just because of the power needed to be able to run all the different types of control,” she says. But industries including automotive, in particular, have been pushing vendors lately to extend more PAC-like capabilities into smaller, lower-cost systems, Chick notes.

GE Fanuc’s PACSystems family currently accounts for “between 30 percent and 40 percent of our sales,” Chick estimates, “and they’re growing at a phenomenal rate—in triple digits.” She figures that PAC sales will zoom past 50 percent of the company’s total controller business some time this year or in 2009.

New battleground

 Chick notes that GE Fanuc and other PAC vendors are increasingly giving the vendors of distributed control systems (DCS) a run for their money in so-called hybrid applications. On a corn flakes production line, for example, a single PAC system can handle both the batch production process traditionally controlled by a DCS, as well as the material handling and packaging control at the end of the process, she says.

Even in oil and gas industries, PACs can play a larger role, Chick continues. “We did a lot of oil and gas before, just with our PLCs, where we were doing all the things around what the DCS controls. We would do some of the pipeline control, or moving parts around on a platform, or whatever they wanted to do, and then the DCS was doing the actual refinery parts. But now we can bid the whole job,” she says, thanks to the multi-domain capabilities of a PAC. And in some cases, according to Chick, PAC vendors are taking business away from DCS suppliers.

Rockwell Automation executives are quick to agree. “The fastest growing portion of our business is in the process area,” says Deken. “There’s a real battleground in this hybrid area.”

As part of our research for this story, Automation World asked the major DCS vendors about the emergence of this “battleground,” whether they are seeing new competition from PAC vendors, and if so, how they are responding. To read their responses, please go to

One thing seems certain. Market momentum for PACs and controllers with PAC-like capabilities is on the rise. “The number of requests we’re getting at ARC for PAC information has substantially increased in the past year,” Resnick observes. “And we only anticipate it getting stronger.”

Definition of a PAC

The Nov. 20, 2002 “ARC Insights,” by Craig Resnick, of ARC Advisory Group Inc., included the following bullet-point definition of a programmable automation controller, or PAC:

  • Multi-domain functionality, including logic, motion, drives and process on a single platform
  • Single multi-discipline development platform incorporating common tagging and a single database
  • Software tools that allow the design by process flow across several machines or process units
  • Open, modular architectures that mirror industry applications from machine layouts in factories to unit operations in process plants
  • Employ de facto standards for network interfaces, languages, etc., allowing data exchange as part of networked multi-vendor systems.

To download or listen to a Podcast of an interview with ARC's Craig Resnick about programmable automaiton controllers, visit 


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