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RFID Journal: RFID Paves the Way for Road Construction

RFID Journal
Road crews are piloting an application using battery-assisted UHF tags to track asphalt from the time it leaves the asphalt plant to when it arrives at a work site.

 

March 4, 2008 - Minds Inc., a provider of information technologies and advanced automation systems for the hot-mix asphalt industry, has introduced a new application that employs RFID to track hot-mix asphalt from the time it leaves the asphalt plant to when it arrives at a construction site and is dumped into a paver (a vehicle used to lay asphalt on roads and parking lots).

PaveTag, part of the company's eRoutes suite of automation systems for the real-time monitoring of job activities, leverages battery-assisted passive (BAP) ultra-high frequency (UHF) RFID tags and interrogators from Intelleflex. The tags are affixed to the trucks that transport the hot asphalt from the asphalt plant to the site.

"Hot-mix asphalt is a real-time product in the sense that it is made on request, put on a dump truck and has to be delivered to the paver in a maximum amount of time, which is about three hours," says Pierre Vidaillac, president of Minds, headquartered in Boisbriand, Quebec.

During the asphalt-transportation process, it is vital to measure tonnages, time and delivery location because these metrics are part of the hauling cost equation. Monitoring generally involves a worker manually checking delivery at the paver, and sometimes another at a truck scale (typically located at the asphalt plant), where tonnages are weighed. But tracking the process that way isn't very accurate, Vidaillac says.

According to Vidaillac, other tracking technologies were considered when developing PaveTag. GPS was rejected because the majority of dump trucks that haul the hot-mix asphalt are rented-truckers generally don't like to be tracked in real-time, he says, and since customers don't own the trucks, they aren't in a position to force the truckers to use GPS technology. "And active tags were too expensive, so the battery-assisted passive tags work well," Vidaillac adds, explaining that BAP tags offered a good read range regardless of the direction in which the tag is oriented relative to the RFID interrogator.

At its factory, a hot-mix asphalt company attaches the BAP to the back of a dump truck. When the truck approaches the asphalt plant's loading dock, a fixed interrogator reads its tag; the tag's unique ID number is associated with a specific delivery order. A paper ticket is printed showing both the tag number and delivery information (such as where the load of asphalt is going, for example, and the time it needs to be there by). That data is then transmitted via the Internet to a secure server housed at Minds' headquarters.

An RFID read of the tag documents when the truck leaves the asphalt plant. As the vehicle approaches the paving machine, a fixed interrogator on the paver culls the tag's ID number and, via GPS positioning and GPRS communications on the paver (also provided by Minds), that data is transmitted back to Minds' servers.

For each load, the PaveTag system can collect or calculate the time the truck arrives at the asphalt plant, receives its load of hot-mix asphalt, leaves the factory, arrives at the paver, dumps its load into the machine and leaves the site (the system is not currently designed to track the load-weighing process). At any given time, Vidaillac says, customers can access reports on the data via the Web, and also by using SMS messaging.

Ultimately, Vidaillac notes, the data can help customers-typically asphalt manufacturers-to optimize delivery schedules so that the dump trucks never need to wait at a paver to dump their loads of hot-mix asphalt, or that the paver never has to stop and wait for a delivery. The software is designed to compute transportation and waiting time by tracking all RFID reads and the time in between them, and by correlating that information with the tonnages each hauler can carry. "This tool helps you schedule better so the paving machine doesn't stop, and the truck doesn't wait," Vidaillac says. "It helps you get your operation as smooth as possible."

PaveTag was used in a pilot in the summer of 2007, and Vidaillac says many of Minds' customers are interested. At least two companies have ordered the PaveTag system thus far, he says-one in the Netherlands, another in Belgium-though he is not at liberty to name them at this time.

The tags operate in the 902-921 MHz frequency band and comply with EPCglobal's proposed Class 3 standard. Specifically, PaveTag leverages the Intelleflex SMT-7100, which has an antenna configured to perform well around liquids, metals and other RF-unfriendly conditions that can interfere with RF waves.

The tag incorporates Intelleflex's patent-pending "inverted F-plane" antenna design, which the tag maker says helps improve the tag's readability around metal by exploiting the tendency of RF signals to bounce off nearby metal objects. It features a durable casing designed to protect it against physical impact and damage, and also has an IP67 rating, signifying its protection against impairment due to moisture, dust and vibration. The tag can be mounted via adhesives, screws or plastic cable ties, and offers a read range of up to 50 meters.

 

Source: RFID Journal: RFID Paves the Way for Road Construction