Abstract
Keywords
Tyre, Wireless Data Transmission, Antenna, Batteryless Power Supply, Piezoelectric Film
Abstract
Although tyres represent the physical interface between road and vehicle, up to now chassis control systems are not able to get direct information concerning forces acting at tyre-road contact point. At the moment the only existing wheel electronic application is the Tyre Pressure Monitoring System, consisting of pressure and temperature sensors located in the valve together with electronics for signal conditioning and data transmission and a battery for the power supply. Data rate is very low since both temperature and pressure change slowly and strategies are provided in order to minimize power consumption. The output of the system is just a warning to the driver. Different and much more demanding conditions occur if sensors (for example accelerometers) must be sampled at high frequency and data must be sent continuously to provide information for a real time control system. In this case a battery is no more sufficient to guarantee an acceptable time duration and alternative solutions for supplying sensors and tyre electronics must be evaluated.
In the EC funded APOLLO project possibilities to gather information at tyre level and to transmit data to the vehicle electrical systems are investigated. This paper deals with electronic aspects concerning the development of a mechatronic demonstrator, in particular a communication interface and a battery-less power supply for a wheel/tyre system and its integration with vehicle electronic systems. Data communication section provides an overview of existing wireless sensors as well as established and emerging automotive wireless applications like Remote Keyless Entry and Bluetooth. Specific requirements of the APOLLO demonstrator are presented and a discussion of main issues concerning bit rate, allowable bandwidth, communication protocols is provided. Tightly connected with communication interface, power supply aspects have a fundamental role in the system definition. Active radio transmission, needed by high data rates, involves a power consumption of more than 10mW: an overview of batteryless applications and technologies is provided and a more accurate analysis of energy scavenging methods (mechanical to electrical energy conversion) and inductive power transmission is performed.
The mechatronic demonstrator has been conceived in order to perform tests on two selected solutions: an inner liner mounted piezo generator and a medium frequency air coupled transformer with secondary windings integrated in the tyre. Power conversion topologies and first measurement results are shown. Mechatronic solutions are described with reference to the harsh environmental requirements for electronics inside the tyre.