Development of a Torque Measurement Method on a Rotating Shaft Using a Battery-Less Sensor

This paper describes the design, fabrication and evaluation of a TDMA (time division multiple access) passive wireless torque sensor using 2.45 GHz surface acoustic wave (SAW) delay lines. The SAW torque sensor consists of a sensor element fabricated on a LiNbO₃ substrate and a support element. The sensor element is a strain-detection thin substrate, on which an interdigital transducer (IDT) and reflectors are fabricated. The support element converts torque force to strain that changes geometrical dimensions of the sensor element. Torque measurement was successfully demonstrated in a torque range of -1000~1000 Nm under static condition. The influence of rotation on wireless transmission of the sensor was also investigated. On condition that a shaft with the sensor was rotated step by step, we found that wireless communication was successfully demonstrated using two flexible antennas and a power divider.