Passive Wireless Sensor Research Articles

Passive Wireless Strain Monitoring of Tire Using Capacitance Change with Tuning Circuit

Reliability of automobiles is increasingly demanded. To prevent burst of tires, smart tires are currently under development. Most of the smart tires have integrated or attached sensors to measure deformation or internal pressure of tires during a long period of service. The embedded sensor enables highly precise measurement of road surface friction, and the precise friction measurements make more efficient anti-lock braking system (ABS). In a previous study, the authors proposed a new wireless strain monitoring method that adopts the tire itself as a sensor, with an oscillator circuit. This method is very simple and useful, but it requires a battery to activate the oscillator circuit. In the present study, the previous method for wireless tire monitoring is improved to produce a passive wireless sensor. A specimen made from a commercially available tire is connected to a tuning circuit comprising an inductance and a capacitance as a condenser. The proposed method enables us to measure an applied strain of a specimen wirelessly, without any power supply from outside. This new passive wireless method is applied to a specimen and an applied strain is measured. As a result, the method is experimentally proved to be effective for the passive wireless strain monitoring of tires.

タイヤの電気容量と同調周波数変化を用いたひずみ無線パッシブモニタリング(モニタリング,OS.6 折り紙・針金/スマートストラクチャ)

Safety of automobiles is increasingly demanded. To prevent burst of tires, smart tires are currently under development The embedded sensor enables highly precise measurement of road surface friction, and the precise friction measurements make more efficient anti-blocking-system (ABS). In a previous study, the authors proposed a new wireless strain monitoring method that adopts the tire itself as a sensor, with an oscillator circuit. This method is very simple and useful, but it requires a battery to activate the oscillator circuit. In the present study, the previous method for wireless tire monitoring is improved to produce a passive wireless sensor. The capacitance change of tire causes changes of the tuning frequency. This change of the tuned radio wave enables us to measure the applied strain of the specimen wirelessly, without any power supply from outside. This new passive wireless method is applied to a specimen and the static applied strain is measured.

Passive wireless actuator control and sensor signal transmission

A new wireless communication method, based on absorption modulation, is presented for bidirectional data exchange between a small implanted module and an external control unit. The implanted module containing actuators and sensors operates without a battery or active RF transmitter. Energy and remote control data are received from an external RF field. The retransmission of sensor data is carried out on the same RF field by modulating the absorption rate. The field of application is multichannel telemetry and closed-loop operation of feedback control systems within long time periods but short distances. Almost any type of actuator and sensor can be supplied and operated, since the energy transfer exceeds 50% efficiency and the information capacity may exceed 1 Mbit/s. Except for the small loop antenna, the whole circuit may be realized on a substrate or hybrid.