Passive wireless strain monitoring of tyres using capacitance and tuning frequencychanges

Abstract

In-service strain monitoring of tyres of automobiles is quite effective for improving thereliability of tyres and anti-lock braking systems (ABS). Conventional strain gauges havehigh stiffness and require lead wires. Therefore, they are cumbersome for tyre strainmeasurements. In a previous study, the authors proposed a new wireless strain monitoringmethod that adopts the tyre itself as a sensor, with an oscillating circuit. This method isvery simple and useful, but it requires a battery to activate the oscillating circuit. In thepresent study, the previous method for wireless tyre monitoring is improved to produce apassive wireless sensor. A specimen made from a commercially available tyre isconnected to a tuning circuit comprising an inductance and a capacitance as acondenser. The capacitance change of the tyre alters the tuning frequency. Thischange of the tuned radio wave facilitates wireless measurement of the appliedstrain of the specimen without any power supply. This passive wireless method isapplied to a specimen and the static applied strain is measured. Experimentsdemonstrate that the method is effective for passive wireless strain monitoring of tyres.