Sensors have an increasingly important, if not essential, role in the automotive industry. Just think, for example, to those used in engine management and it’s easy to see how vital they have become. In such a framework, now consolidated over decades, one component appears to have been left behind despite its importance: the tyre. The data sent by current sensors are already very useful. Starting with pressure and temperature, these allow us to access much more information, but the industry is looking ahead and thinking of tyres capable of establishing a close dialogue not only with the vehicle but also with road infrastructures, via connections that use 5G networks. As of now, it is possible to offer many useful services and information, for example, to road fleet managers as well as construction or agricultural vehicles, aimed at maximizing efficiency, reducing machine downtime, and increasing operational safety. Services such as Continental's ContiConnect, Goodyear's SightLine or Pirelli's Cybertyre are just examples of platforms and services that we can find also in other programs by Toyo Tires, Bridgestone, Michelin, Nokian, Hankook and Apollo. The CyberTyre used for the McLaren Artura hybrid supercar uses sensors integrated in the tyre casing and the data thus generated is processed using software created by Pirelli and processed by the car's electronics. If winter tyres are fitted, the system, which recognizes the tyres fitted, will warn the driver of any different speed index. Pirelli's idea is that the vehicle will "know" which tyre is using and make the most of the characteristics of the tyre and its interaction with the car, such as adjusting the active suspension and optimizing ABS or ESP systems. Looking at other examples, we could mention that the SightLine platform for vans and light commercial vehicles can estimate tread wear and the grip of the road surface and that the ContiConnect has similar characteristics.
Adding value
The bottom line is that tyres will be able to communicate road conditions as well as their own status in real time, connecting not only to the driver but also, via a cloud, to other vehicles and infrastructure. Analysing tyre load history allows insights into driving behaviours, and this knowledge can help better understand how to develop tyres to match drivers' needs. There is also broad consensus on the fact that sensors bring a series of advantages for end users, fleet managers and for tyre retailers and vehicle manufacturers. Cloud platforms, together with related apps, allow for example to monitor heavy-duty tyres and see their behaviour over their entire life cycle, helping users to work more sustainably and safely and development teams to create better products. The type of sensor and the complexity of the data sent can vary according to customer needs: sensors mounted in the tyres, more precise and versatile than those in the valve stem, provide more accurate measurements, which are collected in a data logger and combined with devices placed on the axles of the vehicles to detect the stress a tyre has to bear more accurately, estimating wear and tear and alerting to the need of an inspection following a sudden and significant mechanical shock.
Highly evolved sensors
Future tyre sensors are expected to be easy to produce and inexpensive, given their future widespread adoption, and should store the ID of the tyre itself. Tyres, which are normally subject to deformations, vibrations, and impacts, are not the ideal environments for electronic components, taking into account that such “intelligent” tyres must offer the same safety, integrity and durability as standard ones, with the weight of the sensor imposing additional design solutions. If placed inside the casing, then, given its inaccessibility, it must function (without causing detachments or cracks) for the entire useful life of the tyre, including an additional period as a retread. Ease of connection and integration with telematics systems is another key requirement, as are technological improvements that will increase data transmission speed without reducing battery life. The need for future sensors to be particularly advanced also comes from their being important suppliers of data for autonomous driving systems: their information will in fact complete the "perception" of the environment, so necessary for unmanned driving.
“Layers” of data for autonomous vehicles
The ability of a tyre sensor to understand road conditions will in fact be fundamental to guarantee safe and high performance for autonomous vehicles: today it is possible to "see" the condition of the road surface with video cameras, but it is not possible to "feel" it with the sense of feel that a tyre, in direct contact with the road, has. By combining the information from the sensors (a further "layer" of data) with vision-based methods, it is possible to obtain good and reliable estimates on the state of the road even in conditions in which vision systems are negatively affected, such as night driving and adverse weather conditions. The current landscape of sensors and technology is rather different from when we started working on sensors dedicated to tyres: pervasive connections and intelligent systems will help vehicles make effective and safe "decisions". Future developments include connecting tyres to the 5G network, to other vehicles and surrounding infrastructure – it's a V2X, Vehicle-to-Everything link – to issue alerts about potentially dangerous road conditions. Entering sensor data and detailed vehicle information is already possible using existing technologies, such as CANbus or ISObus, and a strong integration with Android Automotive is conceivable, an operating system that allows for digital functions even in the absence of a smartphone.
In the end we still need physical wheels
In recent years, almost every automotive paradigm has been challenged, except for wheels and tyres, whose life promises to be very long. Even if hidden, the changes are there: the battery packs of EV electric vehicles increase the weight and significantly modify its distribution. The tyres must, therefore, be able to cope with these new characteristics, which means stiffer sidewalls, less rolling resistance, and a more resistant tread to manage the almost instantaneous torque delivery. In fact, a vehicle with a combustion engine equipped with EV tires would seem less comfortable while the opposite assembly would have a negative effect on durability. The powertrain of an EV is much quieter and therefore rolling noise is more evident: the industry has developed solutions for these aspects, such as specific designs for casing and tread and sound-absorbing materials inside the cavity. Low rolling resistance is also required for these tyres because friction directly affects the distance covered. The tyre production process is linked to the optimization of rolling resistance, which can be precisely measured with dynamic and laboratory tests. Mastery of materials and production processes requires not only complex engineering know-how but also virtual modelling, numerical simulation and physical product evaluation.
Established traditions for new tests
A company that for decades has provided customers and automotive engineers with the necessary equipment for dynamic tyre testing is the German Kistler, whose equipment is used, among other things, by Megaride, a spinoff of the University of Naples of which we have already talked about in the pages of this magazine. Kistler's sensor hubs measure rolling resistance, high-speed uniformity, wear, and mechanical resistance of the tyre on the road and in the laboratory and are also used for experimental validation of numerical models and tyre dynamics. Force transducers and accelerometers allow the acquisition of actual load, dynamic data, and useful information to minimize the levels of NVH - Noise, Vibration and Harshness perceived in vehicles. The Kistler Roadyn racing is very sophisticated and, thanks to its sophisticated transducers, is used by many motor sports teams. The wireless KiRoad HDR measures wheel forces to investigate vehicle dynamics, performance, and tyre stability; its long-distance telemetry uses Wi-Fi at the 2.4 GHz frequency and can be used with various RoaDyn measurement platforms. On the other hand, the system consisting of the RoaDyn P530 instrument and the P5MT sensor hubs, measures in the laboratory the dynamic behaviour of a tyre, the response to impact and its power density spectrum, a measure of how the force of a possible impact is distributed as the frequency varies. This measurement takes place by rotating the tyre against a cylinder designed to simulate a collision; jBEAM software performs data analysis and then reports the results. To conclude, we think that any disruptive innovation must be preceded by a correct understanding of physics, the result of accurate measurements. After changing the creation and distribution of power in a vehicle, its mass distribution, and the management of additional weight, isn’t there also a need to reinvent the wheel? Probably not, but there will always be a need for better wheels, and for this, both its daily and experimental functioning must also be measured in the field.
