Manufacturers using real-time location systems to track work in process

Cheaper active RFID and a plethora of wireless networking and sensor choices are driving RTLS adoption, analysts say.

Wireless networks that can track the location of electronic sensors to within centimeters are leading to new advances in asset management in manufacturing. Called real-time location systems (RTLSes), they’re also taking the slack out of production and making workers safer, according to users and industry experts.

RTLSes are taking off especially fast in hospitals, where frantic workflows and frequent emergencies cause medical equipment and other life-saving assets to be misplaced just when they’re needed. But analysts say manufacturing and the supply chain are also seeing increased adoption. Meanwhile, the application is helping to fuel the rise of emerging wireless schemes such as mesh networks. It’s also given new life to a much older, niche technology: active (two-way) radio frequency identification (RFID), by far the dominant sensor technology used in RTLSes.

“The adoption of RTLS is pretty much being driven by the adoption of RFID and driving down the cost of tags,” said Ralph Rio, research director at ARC Advisory Group, based in Dedham, Mass. “They used to be a lot more expensive.” But even at a steep-sounding $20 per tag, reusable, active RFID tags can pay back many times by locating critical parts, Rio said.

Location awareness is what differentiates RTLSes from RFID’s traditional purpose of identification, according to Peter Harrop, chairman of IDTechEx, a research firm based in Cambridge, Mass.

“You’re not just detecting that something has gone near to a reader,” Harrop said. “You’re detecting its position in 3-D and, if necessary, you can continue to do that.”

IDTechEx predicts the small but fast-growing RTLS market will reach $666 million worldwide by 2015.

RTLS installations on manufacturing shop floors are most common in the automotive and aerospace industries, with BMW, Ford, Honda, Airbus, and Boeing going public with their stories. But Rio said they’re not going into assembly lines, where stationary devices can read and write to RFID tags as they pass through predictable “chokepoints.”

Rather, RTLSes in manufacturing make sense in less circumscribed places such as the queuing areas where parts, subassemblies and equipment are temporarily stored. Metal machine shops are a good example.

“Usually the floor is organized with all the grinding machines in one area and all the polishers in the other,” Rio said, but sometimes things get rearranged to accommodate rush orders, and equipment and materials can be misplaced. “The work in process can be fairly high value, and sometimes people can have a hard time finding it,” he said.

Harrop, whose company keeps a database of RTLS case studies, described the system that Ford uses to track tens of thousands of finished vehicles it stores in huge parking lots. In the past, finding a car of a particular color, for example, was extremely labor intensive.

“They would send out six people a day to find the damn things,” he said. Now each vehicle has an active RFID tag that identifies its key characteristic to an RTLS that tracks its location. “They have these huge beacons looking down like watchtowers.”

Managers of dockyards in San Diego and New Orleans use similar RTLSes to find shipping containers fitted with RFID tags the size of VHS tapes, Harrop said.

Boeing uses an RTLS to keep track of parts for Chinook helicopters that somehow were getting lost even though security systems showed no one was stealing them. He said a Boeing official told him the company could build two complete helicopters from the missing parts.

In some cases, the items being tracked are people, to ensure their safety in dangerous environments such as mines and oil refineries, according to Harrop. He cited a New York facility that added an RTLS, motivated in part by a 1987 explosion at a Texas City, Texas, oil refinery.

“Fifteen people died,” he said. “For four days, they couldn’t work out who was in there and needed rescuing.”

RTLS enabling asset management in manufacturing 
Asset management is a popular application of RTLSes in manufacturing and the supply chain, according to Rio, who defines the category as “everything you need to repair and maintain an asset.” The assets tend to be those that are critical to manufacturing or distribution -- even inexpensive ones that, when misplaced, can bring major delays and lost revenue.

“In airplane manufacturers, they’ve taken it to the point of applying it to some common tools, just to make sure they don’t get left in a plane,” Rio said. “A wrench left inside a plane is a major issue -- it doesn’t matter if the tool costs $5 or $500. You’ve got to take the plane apart to take the wrench out.”

RTLS-based asset management is also being extended to the exterior lay-down yards that manufacturing and construction companies use to store parts for projects.

“Maybe they’re bringing in a new valve and keeping it in a grassy area,” Rio said. “Sometimes they don’t use it, and grass grows over it and snow covers it.”

RTLS technology choices abound
While the analysts said the vast majority of RTLSes are built around radio frequency networks, a few systems use infrared light and other optical technologies, sometimes by calculating locations through ceiling-mounted, barcoded grids.

Typically, two radio “interrogators” detect the object and use triangulation to specify its location, though some use the angle or speed of arrival, according to Harrop. The RTLS typically has a proprietary database that manages the coordinates and can, in a way, learn to recognize the dimensions of buildings to improve its accuracy.

The radio-based approaches are often gathered under the umbrella of RFID, though they’re technically separate technologies. They vary widely by frequency and network standard, but Wi-Fi is becoming a common method for linking with Wi-Fi-based sensors and RFID readers that support both standards, the analysts said.

Ultra wideband (UWB) is an alternative to Wi-Fi that is getting popular with companies -- including the New York refinery -- that need their RTLS to penetrate obstacles that cause interference, Harrop said. Ultrasound is another approach, though like optical, it occupies a niche. “Within RFID there’s a big choice, within infrared there’s no real choice, and within ultrasound there’s no real choice,” he said.

The specific environment that the RTLS must run in nearly always drives the technology decision. “I like to separate inside the building from outside,” Rio said. “In the supply chain, you typically don’t always have cell coverage. Inside a building, normally there’s some restriction on cell coverage.” 

The result can be a “Russian doll” configuration, said Harrop, in which Wi-Fi, RFID, and cellular network sensors and tags are nested within a broader network that includes Global Positioning System (GPS) satellite networks that expand beyond the warehouse yard to trucks and ships around the world.

Mesh networks, wireless sensors basis of next-gen RTLS
Both Harrop and Rio agree that a leading-edge technology—mesh networks—will underpin a third generation of RFID and wireless sensors for RTLSes. “It really works like the Internet,” is “self-healing” and can stay up when individual network nodes go down, Harrop said. “It’s going to be a big thing someday but it’s got a problem with the power going to the tag.”

Rio said the advantage of mesh networks is that they can be set up quickly by scattering transmission nodes where they can be most effective at detecting the movement of wireless sensors and RFID tags through the RTLS. It helps most in facilities with metals or liquids that interfere with radio waves and therefore require more transmitters to maintain signal strength. It also helps in geographically dispersed locations where Ethernet’s traditional “hub and spoke” model -- especially the wired kind -- isn’t feasible. Mesh networks are already being implemented in some factories for precisely this reason, he said.

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