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Even though automobilesare mass-produced, it's hard to find two that are exactly alike. Indeed, the number of options is nearly limitless—a fact of life that enormously increases the cost of production planning for automobile manufacturers. Special customer preferences must be taken into account for each vehicle—often many thousands of times per day. Yet the business of tracking all these changes is not performed by a mainframe computer. Instead, manufacturers are now using transponders—tiny electronic tags that can transmit data signals through their antennas—to provide vital feedback and help control complex manufacturing processes.
At General Motors' Opel plant in Figueruelas, Spain, for instance, a supervising software system controls production. But, thanks to a data chip in its transponder, each vehicle knows what it needs to receive as it travels down the production line.
Known as MOBY I, the system consists of a matchbox-sized transponder, a read/write device and a data communications module. Before the first piece of sheet metal for a car even begins its passage through the factory, the individual production data for the car it will be part of is downloaded to a transponder mounted on the vehicle skid. As a result, each vehicle remains individually identifiable throughout the production process and can, for example, communicate whether leather or fabric seats are to be installed in it. At each station, the transponder communicates its on-board data to production robots.
The MOBY I transponder uses RFID (radio frequency identification) to transmit data to the machines around it. This offers important advantages over barcode systems, since transponders can store much more information—and the data can be read without visual contact and from any direction, even if the transponder is dirty or its housing has been scratched. But, as Heinrich Stricker, head of Business Development for MOBY Identification Systems at Siemens, points out, "The key advantage is that MOBY transponders are rewritable." That's especially important for quality assurance and production monitoring. Both control and production data can be written to the transponder at the completion of each manufacturing step to provide a seamless product history.
Today there are six different MOBY systems covering a variety of applications. For the auto industry, for instance, transponders need to be heat resistant in order to survive the paint shop. In addition, they should operate without batteries to minimize maintenance costs. MOBY transponders are activated by an induction voltage from a reader, which may be at a distance of about 15 cm from the transponder in the MOBY I system. In the logistics chain, on the other hand, it's especially important that MOBY markers be readable over a distance of up to 3 m. This capability enables transponder-equipped freight on trucks or loading docks to be identified in a matter of seconds.
Seamless Merchandise Tracking.Transponders have become important elements in today's logistics chains. Many companies and research institutions are working to make these devices ever smarter and are also trying to find new applications for them. One such endeavor was Project ParcelCall, which was completed in December 2001. Project participants included Siemens Dematic AG, the Technical University of Aachen, Germany, Philips and Ericsson Eurolab, among others. The project was designed to demonstrate how transponders can be used to track product shipments, and to determine which communication standards would be required. The idea is as follows: Trucks are equipped with readers capable of communicating with transponder-equipped freight items. The transponder information is then transmitted by radio to a central computer. Since the truck is also equipped with a global positioning system (GPS), the addressee or the freight forwarder can use the Internet or a cell phone anytime to determine the exact location of the merchandise.
"The transponders were also equipped with sensors capable of recording vibrations, temperature and humidity," explains Hanno Walischewski, a ParcelCall development engineer at Siemens Dematic. "This means that, for the first time, customers could check the condition of their ordered products online during shipment." They could, for example, verify that a product had been continuously refrigerated.
Siemens experts designed the heart of the track-and-trace system—a server where the data was collected—as well as the user interface for the PC and the cell phone. A key advantage of the ParcelCall system is the fact that all information is communicated using XML, a uniform data format standard that is widely used on the Internet. This consistency is essential to ensure seamless shipment tracing. Most freight forwarders continue to use proprietary tracking systems with somewhat limited capabilities for tracking shipping information across different modalities in the logistics chain.
The final field trial in the project—tracing a truck from Sweden to England—was successful. But it also demonstrated some unresolved limitations in such track-and-trace methods. For instance, data transfer via mobile communications ran into difficulties. Several minutes were often required to correctly transmit the information. And cellular network coverage was poor in a number of locations.
There are other areas in which transponder systems need to be improved. Jörg Schmidt, a research associate in the Department of Logistics at the University of Dortmund, Germany, is familiar with their shortcomings. Schmidt is building a testing laboratory for transponder systems. The devices often encounter difficulties when metallic objects interfere with or altogether block the radio signals. Schmidt and his colleagues are looking into which materials are transparent to transponder signals, how quickly transponders can move past a reader, and how many of the tags can be read simultaneously. This latter function is known as multitag capability and is a critical success factor for future transponder systems. At a supermarket check-out counter, for instance, transponder-tagged merchandise would be able to provide an instant and contactless tally of what was in a shopping cart.
The Faster the Better. A key factor in multitag capability is the data transmission rate from the transponder to the reader. That's because the shorter the time required to transmit each data package, the less chance there is for transmissions from other transponders to interfere with each other. With this in mind, Wolf-Eckhart Bulst and his team of Siemens scientists in Munich are developing transponders that transmit in the gigahertz range (between 2.5 and 24 GHz). MOBY devices, by comparison, operate in the kilohertz or megahertz range.
According to the laws of physics (specifically, those governing bandwidth), the higher the frequency, the higher the data rate. Thus, using higher frequencies, a large number of transponders can be read in a shorter time. But processing such high-frequency signals requires new circuit designs in transponder chips—an area now being studied by Bulst's team.
Energy demand is also a key issue. Here, the lab has developed ultra-low power electronics that enable transponders to transmit across long distances. The extra-high frequency transponders from Bulst's lab are battery-operated and have an enormously long range—some can actually transmit over several kilometers. What's more, it is now possible for the first time to measure the distance between reader and transponder to an accuracy of 1 cm. This makes it possible to precisely locate a given transponder by processing run-time data from several readers, which opens the door to entirely new fields of application. "Our transponders can bring order to even the most chaotic materials flow because many objects can be localized simultaneously," explains Bulst. He envisions applications for the technology in the giant parking lots of auto plants, where several thousand cars must be moved around every day. A computer could easily be used to navigate transponder-equipped vehicles because each would be identifiable. And, Bulst adds, "There's one advantage that makes extra-high frequency technology especially interesting. These transponders can be tracked even where GPS fails, inside buildings and in the canyons between tall buildings. And it can all be done with a very modest investment in technology."
In a few years it will be possible to use simple printing processes to manufacture electronic components from plastic materials. But before that can happen, scientists will have to come up with materials and production methods that will make it possible to manufacture plastic chips and transponders at an exceptionally low cost.
There's no question that transponders are much more versatile than barcodes. They can store greater volumes of data, are rewritable and can communicate information through their antennas. But they still have one critical drawback: They cost too much. Simple transponders now cost less than one euro—but a barcode merely needs to be printed on the product. And that's exactly what researchers intend to do with transponders and the chip inside that makes them so smart. In the future, the intricate electronics will simply be printed like ink on a substrate and incorporated into transponders that will cost only pennies.
Scientists have already succeeded in printing tiny transistors and simple electronic circuits using organic inks. What made this technology possible was the discovery about 20 years ago that organic molecules can be conductive. Alan J. Heeger from the U.S., Alan G. MacDiarmid of New Zealand and Hideki Shirakawa of Japan discovered that certain organic molecules such as long-chain polymers not only have conductive, but also semiconductive properties similar to silicon. This discovery earned the three researchers the 2000 Nobel Prize for Chemistry. "These polymers can be dissolved in certain liquids just like pigments," says Dr. Wolfgang Clemens of Siemens Corporate Technology in Erlangen, Germany. "We can process them just like ink in a printing process, which opens the door to fantastic new possibilities in the manufacture of electronics." Unlike silicon chips, which must be produced in expensive clean-room processes, the polymer ink will make it possible to print electronic circuits in a manner similar to the way newspapers are made. Another advantage is that polymers are flexible. Future polymer chips will be rolled up or applied to flexible surfaces such as fabrics. A transponder woven into a sweater could, for example, inform the washing machine of the water temperature it needs to provide. And in a supermarket, plastic chips could store not only the price of each product, but also its expiration date.
With these and other exciting applications in mind, several manufacturers and research institutions are collaborating in project PODOS, an initiative supported by the German Ministry of Research, to develop the first fully functional polymer chip. In the context of the project, Siemens and chemical giant Merck are jointly developing technologies for printing polymer chips. Merck is contributing its expertise regarding the properties of various polymers. Clemens estimates that plastic chips can be introduced to the market in a few years. "Plastic chips certainly won't replace silicon chips, but they'll create new markets in the low-cost range where electronics are still unavailable," he says.
Polymer experts at Siemens are also working with a consortium of various Fraunhofer Institutes and universities. Their common goal is to learn which processes are practical and sufficiently gentle for printing ultra-thin conducting, semiconducting and insulating patterns on a substrate. Furthermore, high resolution is essential to this process. The smaller the structures that can be printed on chips, the shorter the distance that charge carriers will have to travel. And that, in turn, will make chips faster.
Scientists at the Fraunhofer Institute for Reliability and Microintegration in Munich are currently setting up a demonstration laboratory for roll-to-roll technology. Here's how production would work. The substrate material—such as a plastic film—is fed from a roll through a process sequence that varies with the application. Insulators, conductors and semiconductors must be printed in the sequence required to form the desired circuit. Finally, the substrate bearing printed polymer circuits is rolled up again—allowing chips to be sold by the yard. Also conceivable is a process that would allow chips to simply be printed on product packaging. But it's still uncertain which materials could be used in large-scale production. In addition, even conventional printing techniques still need to be refined in order to print electronics with the necessary level of resolution. What's more, these processes must approach a zero-defect level of quality and reliability. After all, while a tiny flaw doesn't matter in a newspaper photo, it can make all the difference in the world in a transistor.