Charles Murray

October 28, 2014

4 Min Read
Tire Pressure Monitoring Chip Lays Foundation for Autonomous Cars

A tiny new tire pressure monitoring package will fit inside the tire, instead of on the stem, enabling vehicles to gather more information and help set the stage for self-driving cars.

By residing inside the tire, the new system will enable a vehicle's central processors to analyze shocks, velocity, road conditions, and tire wear in a way that's not currently possible. As a result, the new technology could provide another ingredient for the ongoing development of autonomous cars. "As the requirements for self-driving cars increase, it's going to become necessary for the vehicle to know whether the tires are properly inflated, whether they are wearing out, and how much life they have left," Babak Taheri, vice president and general manager for Freescale Semiconductor's Sensors Solutions Div., told Design News. "That information will be needed in order for the car to make decisions."

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Known as the FXTH87 tire pressure monitoring system (TPMS), the new system is said to be the industry's smallest TPMS chip, measuring a scant 7 mm x 7 mm and weighing just 0.3 grams. Inside, it includes pressure and temperature sensors, two accelerometers, a microcontroller, RF transmitter, and low-frequency receiver. Designed for long, low-maintenance life, the package's RF power consumption is just 6 mA.

"These systems have to last 10 years, so we had to come up with very low-power wireless communications," Taheri told us.

The TPMS package will also enhance the car's intelligence in other ways. Temperature sensors will provide data that can be used to calculate tire wear. Inflation data will tell the car how much of the tire is in contact with the road, which in turn can be used to calculate necessary braking force on self-braking cars. Inflation data can also be used to provide a more comprehensive understanding of the car's energy consumption.

Freescale's new chip, the company's third generation of the technology, comes at a time when tire pressure monitoring is gaining momentum around the world. The technology was mandated in the US in 2005, and will soon be required in Europe, Japan, China, and Russia over the next few years. By 2020, with global vehicle sales expected to reach 100 million per year, TPMS integration could approach half a billion units (five per car) annually.

By that time, Freescale engineers believe it will also be critical for electronics suppliers to offer chips that enhance a car's intelligence. "The minimum requirement will be to measure tire inflation in psi," Taheri said. "But we want to take it to the next level, so that more sensor data can be fed into the central processor for analysis."

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About the Author(s)

Charles Murray

Charles Murray is a former Design News editor and author of the book, Long Hard Road: The Lithium-Ion Battery and the Electric Car, published by Purdue University Press. He previously served as a DN editor from 1987 to 2000, then returned to the magazine as a senior editor in 2005. A former editor with Semiconductor International and later with EE Times, he has followed the auto industry’s adoption of electric vehicle technology since 1988 and has written extensively about embedded processing and medical electronics. He was a winner of the Jesse H. Neal Award for his story, “The Making of a Medical Miracle,” about implantable defibrillators. He is also the author of the book, The Supermen: The Story of Seymour Cray and the Technical Wizards Behind the Supercomputer, published by John Wiley & Sons in 1997. Murray’s electronics coverage has frequently appeared in the Chicago Tribune and in Popular Science. He holds a BS in engineering from the University of Illinois at Chicago.

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