Seeking to push the envelope in vehicle mobility, Pirelli S.p.A. is developing ``cyber'' tires and wheels that monitor operating conditions constantly and feed that information into a vehicle's onboard dynamic control systems.
Pirelli also has market-ready tire-pressure monitoring systems under the X-Pressure name that can alert drivers of low-pressure situations any of four ways-optically via a valve cap; acoustically via the onboard electronic management system; via Bluetooth mobile phone technology; or visually via onboard systems.
Pirelli demonstrated these and other extended mobility technologies-including a version of its motorcycle tire-based Safety Wheel System for sport-utility vehicles-recently at the Paul Ricard High Tech Test Track near Le Castellet on the French Riviera.
* The Cyber Tire monitors a tire's operating condition using built-in sensors that transmit information via an aerial positioned inside the tire.
* The Cyber Wheel monitors wheel movements that can be used to evaluate the so-called hub forces by using a special algorhythm of calculation, developed by Pirelli in collaboration with Milan Polytechnic.
* The Safety Wheel System (SWS) uses a pressurized tank integrated into the rim that activates when tire pressure drops below a preset threshhold, re-inflating the tire to the prescribed pressure and alerting the driver of the problem.
Demand for run-flat products from European car makers should double every year through 2010, according to Maurizio Boiocchi, senior vice president of tire products, who noted that vehicles need to be designed for run-flat tire fitments.
Pirelli is targeting its cyber tire development for OE fitment as early as 2008, according to Filippe Massimo, head of Pirelli Labs, based on contracts with two vehicle makers to test it. Pirelli declined to identify which companies it is working with, but Hans-Rudolf Hein, tire engineer with BMW A.G., confirmed that BMW is working with Pirelli on the cyber tire concept.
Pirelli is looking at three levels of its cyber tire, ranging from simple RFID chips to those that can measure pressure, temperature and three directions of acceleration.
This unit offers sensors and electronic data storage within the tire, as well as a transmitter and means of getting data out of the tire. The data can then be fed either into the vehicle's handling and ride-control electronics or into a central database. In the former case, the system can monitor the state of the road and the condition of the tires continuously. In the latter condition, the tire can contain unique identification information, such as age, size, date and place of manufacture.
The cyber wheel is similar, though it can generate less information about the road forces and grip at the tire-road interface. The cyber tire is a more difficult technical challenge because of the flexibility of the tire and the harsh environment within the air chamber.
In each case, Pirelli has designed a tire (or wheel) with permanent instrumentation attached. The instrumentation is designed to record pressures, temperatures, accelerations, footprint area and so on. There is a means of extracting the information from the wheel or tire and transmitting it to the main vehicle electronics.
In particular, speakers said at the presentation, the cyber tire answers one of the main criticisms of the run-flat tire technology. It can record the temperature history of the tire and thus give an estimate of the remaining life left in the tire.
At present, tire dealers will replace a run-flat tire if it has been driven at zero pressure for any distance, even though it may still have some useful life in it. Unfortunately, there is no sensible way to estimate the amount of useful life remaining in a run-flat tire. Francesco Gori, managing director of Pirelli's tire sector, said that Pirelli does not allow dealers to repair its run-flat tires.
With the cyber tire, however, the sensors permanently attached to the tire can record the pressure, the time and temperature history, and this can then be correlated with experimental results to estimate remaining life. This can, in theory, be done while the tire is still mounted on the vehicle. Thus, a driver knows exactly how much further he or she can drive with the tire fully deflated.
Beyond this, however, the cyber tire offers a potential for substantially improved vehicle safety. At present, vehicle electronics can only estimate many of the variables they need to work out the vehicle trajectory. With sensors in the tire, measuring contact patch, grip and acceleration, many of these variables can be measured with sufficient accuracy to dramatically improve estimations of the vehicle trajectory.
One of the most challenging aspects of this technology is to transmit the data from the sensors and internal chip to the vehicle chassis. Mr. Boiocchi said Pirelli believes it has solved this problem using a kind of conducting fluid applied on the inside of the tire. He said the technology is patented, but Pirelli expects to be able to license the technology to other tire makers in order to create a global standard that can be offered by a number of different tire makers.
He said the antenna has to match the impedance of the rest of the system, so a good antenna needs to be made from specific materials that have the right levels of resistance. Mr. Boiocchi said the solution came out of a joint development project between Pirelli cables and Pirelli labs. He said the material is not metallic and is not a wire and can be applied using Pirelli's Modular Integrated Roboticized System (MIRS) of making tires or using more traditional methods.
In terms of delivering safety following a severe pressure loss, the company demonstrated two main systems. The first is the well-established self-supporting sidewall technology, suited to most sedans.
The second was the SWS in which compressed air is stored within the wheel rim and released through a pressure sensitive valve when pressure within the tire chamber falls below a pre-determined level. The air in the rim is typically stored at 145 psi and may have a volume of between 10 percent and 50 percent of the volume within the tire chamber, thus allowing approximately one full charge of air per tire.
Pirelli said this is enough to bring the vehicle to a stop in perfect safety and under full control, even in the case of a large hole caused by a screw or bolt puncturing the tire and immediately falling out of the hole.
The SWS is suited to all vehicles, from motorcycles to large heavy SUVs and light trucks. It offers drivers peace of mind that their tires will continue to be inflated to the correct pressure over a period of many months and have the ability to stop in safety should a SWS tire suffer catastrophic pressure loss.
Pirelli's X-Pressure system comprises a small pressure sensor that fits onto a conventional valve stem. The unit weighs less than an ounce, Mr. Massimo said, so the wheel does not need re-balancing once the X-Pressure device is fitted. He said the lowest grade of this product simply changes color when the pressure falls, but more sophisticated versions contain a Bluetooth transmitter and small battery. If the driver has a Bluetooth mobile phone, then the tire pressure valves can talk to the phone and the phone acts as a warning and display.
Historically, sport-utility vehicles have been unable to use run-flat tires with self-supporting sidewalls. This is due partly to the higher weight of SUVs and partly due to the fact that they tend to run on higher tires with larger aspect ratios. Pirelli has a potential solution that can be fitted either at original equipment or as an aftermarket upgrade.
The SWS relies on a high-pressure air reservoir within the alloy wheel. A valve allows air to flow out of the reservoir into the tire, when the pressure in the tire falls below a predetermined level. The actual volume of the reservoir is typically half to one-fifth the volume of air in the tire, but since it is at five times the pressure, there is enough air in the reservoir to completely re-inflate a tire at zero pressure. The high-pressure air reservoir can be refilled at any truck tire service center. It has a second valve-standard on truck tires-designed to accommodate 145 psi within the metal wheel.
This system, in conjunction with a tire pressure monitoring system, is designed to ensure drivers of large vehicles-and motorcycles-have sufficient spare air to come to a safe stop in the event of a catastrophic pressure loss, or to continue to their destination in the event of a gradual pressure loss. Pirelli says that in the normal course of events, the system will keep the tire at its ideal pressure for nine to 12 months.