タイヤの電気容量と電磁誘導変化を用いたひずみ無線パッシブモニタリング

Abstract

Strain monitoring of automobile tires in-service is quite effective for improving the reliability of tires and ABS (Anti-lock Braking System). In a previous study, the authors proposed a new wireless strain monitoring method which is adopted in the tire itself as a sensor with an oscillator circuit. This method is simple and useful, but it requires a battery to activate the oscillator circuit. In the present study, a new passive wireless strain measurement system utilizing capacitance change of tires is proposed and experimentally investigated. The system consists of external antennas and strain sensor with an inductance-capacitance (LC) resonant circuit. The wireless system utilizes electromagnetic coupling between two inductors of the antenna and the sensor. This method enables us to use a part of an actual tire as a capacitor of the LC circuit. Deformation of the tire causes a resonant frequency change of the sensor. This resonant frequency change is measured as a change in the phase angle of the antenna by using electromagnetic induction. Tensile tests are performed and the phase angles are simultaneously measured. As a result, the method is experimentally shown to be effective as a passive wireless strain monitoring of tires.