Non-contact human machine interface based on bio-interaction with wireless power transfer features

This paper presents a non-contact human machine interface to sense the position or bio-activity of human body. Based on the electrical response of power transferring coil to the physical shapes, impedance, and dielectric constant of human body, the proposed architecture can be easily integrated and allows the smart devices to read information including physical position or cardiorespiratory activity of human body. A commercial WPT/NFC coils incorporated in an LC resonate tank senses the human activities and changes the oscillating frequency accordingly. High sensitivity is achieved by utilizing a mixer that down converts the resonant frequency to baseband from a carrier frequency of several MHz. Experiment was carried out by correlating the frequency shifts to the hand-coil distance. As an example, the result shows good indication of hand position when the distance is below 10mm. By proper arrangement of multiple coils, the information of hand position can be easily extracted through further processing by smart devices.