A Wearable Walking Gait Speed-Sensing Device using Frequency Bifurcations of Multi-Resonator Inductive Link

This paper describes a wearable inductive sensing system to monitor (i.e., sense and estimate) walking gait speed. This proposed design relies on the multi-resonance inductive link to quantify the angle of the human legs for calculating the speed of walking. The walking gait speed can be used to estimate the frailty in elderly patients with cancer. We have designed, optimized, and implemented a multi-resonator sensor unit to precisely measure the angle between human legs during walking. The couplings between resonators change by lateral displacements due to walking, and a reading coil senses the frequency bifurcations, corresponding to the changes in angle between legs. The proposed design is optimized using ANSYS HFSS and implemented using copper foil. The Specific Absorption Rate, SAR, in the human body is calculated 0.035 W/kg using the developed HFSS model. The operating frequency range of the proposed sensor is from 25 MHz to 46 MHz, and it can measure angles up to 90° (-45° to +45°). The measured resolution for estimating the angle shows the capability of the sensor for calculating the walking speed with a resolution of less than 0.1 m/s.