Passive wireless strain monitoring of a tire using capacitance and electromagnetic induction change

摘要

Strain monitoring of tires in-service of automobiles is quite effective for improving reliability of tires and an anti-lock braking system (ABS). A previous study by the authors presented a new wireless strain monitoring method that adopts 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. The present study proposes and investigates a new passive wireless strain measurement system using capacitance change of tires. The system consists of external antennas and strain sensor with an inductance-capacitance (LC) resonant circuit. This wireless system uses electromagnetic coupling between two inductors of the antenna and the sensor. This method allows use of a part of an actual tire as a capacitor of the LC circuit. Tire deformation changes the sensor's resonant frequency. This resonant frequency change is measured as a change in the phase angle of the antenna using electromagnetic induction. Tensile tests are performed and the antenna phase angles are measured during the tests. Consequently, experiments show that this method is effective for passive wireless strain monitoring of tires.