RFID tags go underground

Confidex, a company with expertise in RFID design, manufacturing and engineering, has supplied more than 10,000 of its Ironside UHF Gen2 hard tags to the London Underground.

The tags are being used to improve escalator maintenance.

The underground escalators carry more than three million passengers every day. Most commuters and tourists don't give the travelling metal staircases a second thought; a fact that is a testament to the reliability of the system and the care taken over the maintenance.

The steps that make up these escalators are subject to constant wear from the feet of passengers and from the mechanical movement on the escalator track.

A failure in step could cause serious injury and if an escalator step fails during rush hours, lives could be at risk and serious disruption to travellers would result.

To prevent this, an inspection/maintenance regime has been implemented in the underground that ensures the structural integrity of every step is checked at least once during every year.

With almost 30,000 escalator steps — in almost 200 escalators — needing to be checked, this requires significant effort by engineering staff.

To address the need for faster, more accurate and more cost-efficient maintenance, RFID technology was chosen. A decision was made early on to use UHF Gen2 (ISO-18000-6C) technology as the only viable technology able to read tags attached on metal from a distance.

The 'step tracking system' was developed as the maintenance management solution. This uses a PDA with RFID reader (Nordic ID's PL3000 ruggedised handheld reader) mounted on a cradle beside the escalator and application software to read and write information on the tag.

The tags to be used had to last in the challenging environment of an operating escalator, with vibration, temperature variation, grease and dirt as well as magnetic fields all being a factor.

The tags are installed under the steps — attached with acrylic adhesive — and in spite of the tough environment and constant movement, no tag has detached from its escalator step over the two-month trial. In the future, all new steps will come from the manufacturer with tags riveted on them.

Operational deployment has now started across the Bakerloo, Central and Victoria lines and other stations where London Underground is responsible for escalator maintenance.

The tag, which uses NXP's G2XM chip featuring 240 bit EPC, UID and 512 bits of user memory, was an early recipient of SAE's AS5678 certification.