PiezoTag has energy to spare

By David Shaw, ERJ staff report

Coventry, UK -- Further to this morning's story that Piezotag is offering a self-powered tyre pressure monitoring system, ERJ can exclusively reveal that the company has a robust piezo-based micro-generator which can deliver more than enough energy to power a tyre-borne sensor and transmit frequent signals deep into the vehicle.

Malcolm Caley, director of Marketing at PiezoTag said the key component in the micro-generator is a disk of piezo material. This is installed in a robust casing which is attached to the innerliner near the crown of the tread. As the tyre rolls, the disk deforms as the unit enters the contact patch and again as the unit leaves the contact patch. Each incident generates a pulse of energy.

The unit generates more energy at higher speeds, but Caley said that even at 15 km/hour it generates plenty of energy to power both the sensors and the radio frequency transmissions. At higher speeds there is energy to spare either to boost the radio signal, or to power other sensor functions. Future versions can include a capacitor to store energy for 24 hours or so, to provide a pressure reading at ignition-on, before the tyre has started rolling.

While PiezoTag has developed a complete package, including sensor and casing and a means of attaching the whole to a tyre, Caley said the key development is the piezo generator which is unique in the world in terms of its power output and its robust design. He said the company has tested the unit within a tyre on a drum and stopped testing at 40 000 km. When inspected after that distance, the unit showed no sign of mechanical damage or deterioration.

The total package weighs less than 10 grams for a car tyre or 20 grams for a truck tyre, but this has not been fully optimised. It can be fitted either during original tyre manufacturing process, or retro-fitted to an existing tyre by a tyre using industry-standard repair patch technology.

Caley said the piezo disk is supported on a backing membrane. This membrane can be made of metal or polymer, but its deformation and stiffness characteristics need to be tuned to suit the application.

Although PiezoTag has developed the complete package, Caley said the key development is the micro-generator and this component can be adapted for use in different packages. He said he is keen to work with big-name tyre makers or telematics companies to find ways to adapt the micro-generator to their technologies.

Caley said the company was established in 2004, but has been ready to talk with the industry only since about 2009, and in that time the business has had other issues to deal with.

He said, from what we can see, none of the big brands we know in the tyre market or the TPMS suppliers, has been able to do this, whereas we have proved it and have had it independently tested." He said other systems using micro-generators can only send data on a three minute cycle, due to power limitations, but this system can transmit data 12 times a minute.

The company has worked with two big-name tyre makers who have both confirmed the power output of the device, said Caley.

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Website of PiezoTag from Piezotag