Researchers Find That Radar Can Be Used to Detect a Nail in a Tyre Long Before It Goes Flat

Researchers Find That Radar Can Be Used to Detect a Nail in a Tyre Long Before It Goes Flat
Image: Carnegie Mellon University

Your car’s dashboard is a smorgasbord of information when it comes to the health and performance of your vehicle. But the one thing it can’t warn drivers about is when the tread on their tyres has worn out. It’s a safety risk that researchers from Carnegie Mellon University are focusing on with a new real-time monitoring system that relies on radar.

Keeping track of the condition of a vehicle’s tyres is as important as remembering to regularly change the oil in the engine. As the depth of the tread wears away, it can reduce a tyre’s ability to effectively grip the road. Uneven wear can also affect the performance and handling of a vehicle, but it’s something car owners have to manually remember to keep an eye on. There’s no dashboard warning light reminding them to check tread depth, and to further complicate maintenance, most drivers are unfamiliar with what a tyre with a dangerously low tread actually looks like. Sticking a coin in the groove tells you nothing if you’re not regularly performing such a test, and not every driver is responsibly taking their ride in for regular service.

Starting back in 2018, a team of researchers from Carnegie Mellon University partnered with Bridgestone to experiment with using various technologies as a way to autonomously monitor tyre wear. Laser-based systems already exist, and are incredibly precise, but the technology is sensitive, difficult to deploy on a moving vehicle where the tyres are spinning at high speed, and can be easily fooled by debris that builds up in a tyre’s grooves. The eventual solution turned out to be a much older technology — radar — which allows the new Osprey system to detect more than just a loss of tyre tread depth.

Radar might sound like an outdated technology, but highly accurate and modern millimetre-wave radar systems are already in use in vehicles that offer features like obstacle and collision avoidance, as well as intelligent cruise control where the driver doesn’t necessarily have to keep their hands on the wheel while cruising down the highway. Osprey uses millimetre-wave radar components that are already widely available for automotive applications, but mounted in a vehicle’s wheel wells, and focused on the surface of each tyre.

The high-speed spinning motion of a tyre actually improves the accuracy of millimetre-wave radar sensors to sub-millimetre measurements. By bouncing signals off of a tyre and precisely measuring how long it takes them to return, the Osprey system can not only measure the depth of a tyre’s tread, it knows how those measurements have changed over time, potentially giving drivers an estimate of how long until they need to pony up for a new set of wheels.

Osprey combats debris by laying aluminium strips in the groove, which emulate a spatial code. Different grooves have different coded bit patterns encoded using pulse width modulation.

The accuracy of the system’s measurements aren’t affected by dirt buildup, or the presence of snow, which would hinder optical solutions. It can, however, be thrown off by the random rocks and other debris that regularly gets lodged in a tyre’s grooves. To account for this, the researchers embedded metallic strips in a tyre groove, in specific patterns, that the radar can detect. The strips work alongside the metallic strips that tyre makers already add to disperse the buildup of static electricity, and any irregularities detected in the pattern can be ignored, or, such as with a nail, can be brought to the driver’s attention.

In testing, the prototypes of the Osprey system have successfully measured tyre tread depth to within 0.68 millimetres, and have been able to accurately detect harmful foreign objects like nails 92% of the time, pinpointed to within 1.7 centimeters. The metallic strips added by the researchers mean the system won’t work on tyres currently being manufactured, but the team is looking into ways to use other ingredients tyres are made of to detect and filter out the debris that could otherwise reduce the accuracy of the safety system.