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What You Need To Know About RFID

RFID—radio frequency identification—technology can help manufacturers keep better track of vehicles-in-becoming (i.e., parts, subassemblies, etc.) and even after the sale. Here’s how.


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Although they probably don’t know it, automobile owners have literally grabbed onto radio frequency identification (RFID) technology. That’s because it’s found in ignition key-based security systems. The keys in these systems include a transceiver, a transponder containing a unique identification encryption algorithm, and battery working together to immobilize a car until the owner wants to drive away. These systems also make cars emit obnoxious squawks and open the door locks.

Now RFID is poised to take off in automotive manufacturing, replacing squawks with beeps and unlocked doors with open access to a wealth of information throughout the supply chain.

How? RFID tags are becoming more versatile and in some cases consumable. Nowadays RFID readers can read multiple tags—even conventional bar codes. And RFID tags are now providing "location, location, location."

Frequencies and RFID

The packaging of mid-range, narrow-band frequency tags (typically 12.5 kHz or 25 kHz bandwidths) has dramatically changed during the last couple of years. For example, flexible RFID labels from Texas Instruments (Dallas, TX) come in two sizes, the smallest measuring 1.8 by 1.8 in. and 15 mils thick—thin enough to be printed on standard printers. Each tag provides 256 bits of user-programmable read/write memory, partitioned into eight 32-bit blocks. Another block, written during manufacturing, contains a unique, sequential, 32-bit identification code, which provides enough numbers for 4.3 billion unique labels.

The label readers operate around 13.56 MHz, the same frequency used internationally for contactless smart cards. No FCC license is required for U.S. users. Read distance can be as far away as 1.5 ft. Read speed is 11 milliseconds per tag, though up to 50 tags can be read simultaneously in one second. Labels cost between $0.25 and $1.00, depending on volume.

Currently, FCC regulations restrict 13.56 MHz RFID systems in the U.S. The concern is that boosting the power of an RF signal increases sideband interferences, which can affect other equipment. These restrictions should open up in the next year or so to be more in line with regulations in Europe, says John Pearson, RFID Business Development Manager for Brady Worldwide Inc. (Milwaukee, WI).

Which brings up an interesting point. Contrary to what might be assumed (at least I assumed it), RFID reading distance and frequency are not directly related. "Physics and the government are equally powerful forces on reading distance," says Pearson.

As confirmation, look at the reasons for the recent migration of wireless local area network and RFID technologies from the 450-to-470 MHz narrowband range to the 902-to-928 MHz and 2.4 GHz bands using spread-spectrum technology:

•Operating narrowband RF technology requires an expensive FCC license, which is often difficult to get.
•902 MHz systems cover a large area, which is ideal for warehouse operation and operations involving roving inventory. For 902 MHz spread-spectrum systems, reading distances run 3,000 to 5,000 ft.; for 2.4 GHz systems, 1,200 to 1,800 ft.
•2.4 GHz systems can accept and transfer large packets of data quickly: 1,000 to 2,000 kilobaud, versus 100 to 400 kilobaud in 902 MHz systems.
•Systems based on 2.4 GHz are popular in European and Japanese facilities because the 902 MHz systems conflict with GSM cellular telephone systems.

Now for the caveats. Large data transfers require either longer transmission times or a faster RFID system. However, RFID systems with high data transfer rates operate over shorter ranges. Therefore, to keep reading coverage constant, more tag readers are required. In numbers, a 50% reduction in reading area requires four times the number of access/read points for the same amount of coverage. This increases system complexity and costs.

The good news is that the 2.4 GHz frequency band is three times larger than 902 MHz band, helping to give 2.4 GHz systems about eight times the raw data speed as their 902 MHz counterparts. However, 2.4 GHz systems provide about one-fourth the coverage.

Ç’est la vie.

About Seats and Savi’s Appliance

Identifying car bodies individually and uniquely gives tremendous flexibility to just-in-time (JIT), work-in-process (WIP), and production work flow in general, says Chris Hook, Senior Manager, Mobile Computing Systems, for Symbol Technologies, Inc. (Holtsville, NY). Plus, "there is the general trend toward increasing mobility, and therefore wireless data capture." These issues become even more critical as OEMs, suppliers, and distributors work on supply chain management (SCM) right to the customer’s garage.

For example, says Pearson, car seat manufacturers are starting to put an RF label inside their seats. The label contains the VIN of the car the seats go into. The manufacturer sequences the seats according to the JIT production schedule on the assembly line. In production, the labels help ensure that the right seats go into the right cars. After production, these same labels act as a deterrent to car theft. To sell the seat from a stolen vehicle, "chop shops" would have to damage the seat to remove the VIN label. There’s no payoff in that.

In this way, RFID’s biggest bang-for-the-buck will probably come from applications that stretch from WIP, through distribution, to the end customer.

One problem: 70, maybe 80, types of RFID tags exist today, says Vic Verma, President and CEO of Savi Technology, Inc. (Mountain View, CA). "Each one is customized for a particular set of applications for which it does a great job. None of them talk to another."

Selecting any one of these tags for multiple applications means balancing compromises. Verma suggests another approach: Use a "data appliance," specifically the Savi Universal Reader—a web-based scanner that reads virtually any RFID tag, from single-chip to multi-chip systems, passive to active, you name it. The goal, explains Verma, is to move the automatic data collection effort away from picking the "right" tag to where the tag doesn’t matter.

In operation, Savi’s data appliance reads the tags and then sends the tag’s data over the Internet to a Savi Data Server. The server aggregates these data from all the different players in the user company’s supply chain. These data are consolidated and then sent back to the user company’s information systems (ERP, MES, or whatever) using XML protocol or simply as a display on a web page.

Savi is using this approach in a pilot for tracking the movement of metal racks from a supplier to the factory, and back again for reuse. The Savi Data Server gathers data about racks, including whether individual racks are empty or full, the rack ship date and when the factory received it, and how long the rack was in WIP. The pilot involves RFID tags from Intermec Technologies/Corporation (Everett, WA); CAPS-TRAC, a graphical container tracking system from Container & Pallet Services (San Francisco, CA); and Savi’s Universal Reader and Data Server.

Car 54 where are you?

SCM is also the reason why RFID is evolving into RTLS—real-time location systems. RTLS involves a number of fixed RF base stations receiving signals from mobile RFID tags. The moment these tags come into the wireless environment, such as a production area ringed by RF base stations, the tag is RF-visible to a monitoring system. Using classic triangulation, RTLS is able to locate and track the tags—and the tagged items—within ±10 ft.

Pinpoint Corporation (Bedford, MA) sees three initial uses for RTLS in the automotive industry. The first, explains Armando Viteri, PinPoint’s President, breaks centralized production control into some sort of pull-based production system: The RTLS tag acts as an electronic traveler for the vehicle, and it helps people locate that vehicle—exactly. As a practical matter, the first pilots are in tagging tools and carriers, not the vehicles themselves. As a result, though, production wait and queue times are reduced, as well as the effort to track these items.

Another RTLS application is to tag the actual manufactured item from the very beginning. Yes, this is already being done with thermal-jacketed RFID tags, but that only provides license plate-type information. For about the same cost, says Viteri, an RTLS tag can provide the OEM with location data. This can help, say, when vehicles are temporarily pulled out of production and put into some holding area. RTLS can track these vehicles, locate exactly where they are in and out of production, and automatically log the vehicles back into the system as they come back into production. With their location known, the vehicles can be randomly placed in the holding area—even taken off a confined conveyor belt.

Up to this point, conventional RFID tags serve no useful application after the manufacturing line. However, Viteri proposes making RTLS tags a permanent part of vehicles. Now imagine a trucker with a shipping manifest of VINs to load. A wireless computer with RTLS can map exactly where the cars to be picked up are parked. The RTLS tags can even confirm the load against the shipping manifest as that truck rolls out of the lot.

Imagine now the car is sold. The RTLS tag can act as a portable maintenance database on the customer’s car. When the customer pulls into the service bay at a local repair shop, a computer reads the tag to determine exactly who the customer is, what work was done on the vehicle, what preventive maintenance needs to be done, and who to bill.

"The original idea of tagging the parts and tools associated with vehicle manufacturing is now evolving to a cradle-to-grave use of the tags—not just in manufacturing, but throughout the life of the car and wherever it is in the supply chain, regardless of what stage it’s at," sums up Viteri.


RFID Evaluation, Selection, and Implementation

• Analyze application needs relative to read/write, frequencies, amount of information to be stored on a tag, and operating environment.
• Determine additional and future automatic identification needs.
• Design custom-engineered RFID packaging systems adaptable to individual applications and environments, including extreme temperature, harsh chemical, and potentially volatile fumes.
• Evaluate, recommend, and design tags and mechanical tag attachments that will remain affixed to measured products using adhesive or mechanical means.
• Conduct user training regarding use, installation, operation, and available information obtained from automatic identification systems.
• Direct post-implementation system evaluations, with special attention on maintenance service and examination of upgrade or new technologies offering additional cost efficiencies.

Source: Brady Worldwide Inc.



RFID is a system using low-power radio signals to transfer (read or write) data between an RFID device and an RFID reader. Historically, according to Intermec Technologies/Corporation (Everett, WA), RFID "devices" were either tags or transponders. Tags do not actively transmit data to a reader; transponders (TRANSmitter + resPONDER) do. Nowadays, the terms "tags" and "transponders" are used interchangeably, though transponders are typically called "active" tags, while "passive" tags are those devices that reflect or backscatter transmission from the RFID reader.

Tags can be read-only, read/write, or write once/read many (WORM). Passive tags contain permanently stored identification numbers and varying amounts of other information. Active tags typically use a battery to power the tag transmitter and receiver, though some passive tags use battery power to maintain large amounts of memory or to modulate the reflected RF signal. Generally, active tags have more components than passive tags, so they are larger and more expensive. Also, their life is directly related to battery life. Either tag can be written by the manufacturer or the user, though the assumption with active tags is that the user will be writing data on the tag. Tags can be attached to or embedded in the objects to be identified.

RFID readers can be either stand-alone handheld devices or fixed devices controlled by a host computer.


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