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Michelin Uses RFID to Track Tire Pressure and Tread for London Bus Company

The tires on Stagecoach London's double-decker buses are equipped with passive EPC RFID tags and wireless air-pressure sensors that record a tire's pressure and tread depth within a matter of seconds.
By Claire Swedberg
During a tire inspection, the iProbe+ device reads the unique ID number encoded to the RFID tag, within a range of up to 50 centimeters (19.7 inches), in order to identify which tire is being tested. The iProbe+ also reads the pressure sensor, by exciting the tire's surface acoustic wave (SAW) pressure sensor via a low-frequency (LF) 125 kHz transmission. In response, the passive sensor uses the power from the reader's signal to transmit its own signal along the 433 MHz RF band, with the exact frequency dependant on the tire pressure. Based on the specific frequency of the sensor's signal, the iProbe+ then calculates the tire's pressure. Finally, the operator utilizes the handheld device to determine tread depth. The pressure and tread-depth data is linked with the tire's unique ID on the handheld unit, and can be forwarded to a back-end server, either via a Bluetooth connection or by docking the handheld.

The RFID tags—including the chip and antenna—have been seven years in development, Michelin reports, and the company currently has 20 patents pending. The technology is intended not only to be built into Michelin's tires, but also to be made available to other tire manufacturers, for use on buses and trucks for which storing data regarding tire quality is important. The tags, which measure 5 centimeters (2 inches) in length, come with 512 bytes of data storage capacity.


Many buses operated by Stagecoach London have been fitted with Michelin’s X InCity tires that have integrated EPC Gen 2 passive RFID tags and wireless air-pressure sensors.

Without the TPMS system, Michelin reports, it typically takes operators a total of 15 minutes to check the pressure and condition of every tire on a bus or truck, and to then record that information.

In the absence of an RFID solution, the staff must remove the cap from each tire's valve and attach a pressure gauge in order to measure the pressure. The workers must then manually write down or input the resulting measurements, as well as the serial number printed on each tire's outer sidewall. The serial number can sometimes be difficult to read if the tire has been rubbed or scraped against curbs or other obstacles, says Jean-Claude Pats, the head of Michelin Europe's trucks division.

"The idea is not to do it more frequently," Pats explains, "but to do it faster, more reliably, and to automatically generate data that can be used to issue a report to the customer, and can be stored in a database that will be used to follow the tire performance."

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