Torque measurement with tunable metamaterial and a modified Doppler radar

Torque is a key parameter in any type of drive system. Real-time torque sensing allows to monitor true power transfer, which is crucial for drive control systems, especially in terms of efficiency and safety improvement. However, up to now, there is a lack of available torque sensor technology meeting the high demands within powertrains or robotics, such as robustness against electromagnetic interferences, vibrations and limited installation space. In this work we present a new concept for torque measurement using tunable millimetre-wave metamaterials together with a continuous wave radar chip as read out. The concept is to mechanically translate torque signals into a shift of the metamaterial resonance frequency which in turn leads to a tuning of phase and amplitude of its reflection spectra. Determining the amplitude tuning with in-phase and quadrature demodulation then allows to calculate the torque. We show the feasibility of this concept with finite element simulations. Further, we build a demonstrator providing the proof-of-concept, using a modified millimetre-wave Doppler radar chip for read out. The demonstrator gives a sensitivity for torque measurement of (15.7 ± 0.4) mV/Nm. We believe that our proposed torques sensor concept paves the way towards future torque sensor technology that is suitable for applications in powertrains and robotics.