Battery-Free Wireless Torque Sensor Powered by RF Energy

Conventional dynamic torque measurement usually requires wires and slip rings for supply and data transmission, which shows many drawbacks in terms of device installation, maintenance, durability, and reliability. We, here, present a wireless torque measurement sensor without a battery, which can achieve a long-term and real-time torque monitoring on either static or dynamic rotation systems. The proposed battery-free wireless torque sensor (BWTS) is nondestructive and low cost. The BWTS is equipped with a Koch–Meander hybrid dipole antenna to receive the radiofrequency (RF) energy emitted from a customized reader. The BWTS can be activated at an input power of −15 dBm (
$32 \mu \text{W}$
), and the maximum operational distance in the open air is 3 m. We also study the sampling rate of the BWTS on a dynamic shaft and demonstrate it on the road, which to our best knowledge, is the first successful demonstration of fully self-powered and wireless torque monitoring in a real running car. This work indicates the feasibility of wirelessly powering torque sensors using far-field RF energy, introducing a new power solution to wireless and battery-less automotive sensors.