Noncontact Human–Machine Interface With Planar Probing Coils in a Differential Sensing Architecture

This paper presents a noncontact human–machine interface which is capable of sensing and indicating the position of a human hand that is approaching a probing coil. High sensitivity is achieved by utilizing a structure including two oscillators and a mixer to compare and extract the electromagnetic shift between two probing coils. The probing coils chosen in this system have a planar structure and small size, which can be easily built on a printed circuit board or integrated into a portable device for hand detection. The hand–coil interface is analyzed quantitatively for both the inductive and the capacitive links. Based on the analysis, a circuit model for the hand–coil interaction is presented. The proposed sensing circuit was built on an evaluation board with two commercial planar coils. A small phantom was used to imitate the hand electrical characteristic for a reliable and repeatable experimental setup. The measured results showed a hand-detection sensitivity of 10 kHz/mm at the output of the mixer stage and 30 mV/mm at the final output of the proposed interface.

[1]  M Steffen,et al.  Mobile Noncontact Monitoring of Heart and Lung Activity , 2007, IEEE Transactions on Biomedical Circuits and Systems.

[2]  D. A. Dunnett.  Classical Electrodynamics , 2020, Nature.

[3]  Mohamad Sawan,et al.  A Smart Multicoil Inductively Coupled Array for Wireless Power Transmission , 2014, IEEE Transactions on Industrial Electronics.

[4]  Ivan Müller,et al.  Power Transfer With an Inductive Link and Wireless Tuning , 2013, IEEE Transactions on Instrumentation and Measurement.

[5]  Marian K. Kazimierczuk,et al.  Self-capacitance of inductors , 1997 .

[6]  Steffen Leonhardt,et al.  A Bendable and Wearable Cardiorespiratory Monitoring Device Fusing Two Noncontact Sensor Principles , 2014, IEEE Journal of Biomedical and Health Informatics.

[7]  Hsin-Yu Wei,et al.  Design of a Sensor Coil and Measurement Electronics for Magnetic Induction Tomography , 2011, IEEE Transactions on Instrumentation and Measurement.

[8]  Chin-Shyurng Fahn,et al.  Development of a data glove with reducing sensors based on magnetic induction , 2005, IEEE Transactions on Industrial Electronics.

[9]  J.K. Clapp,et al.  An Inductance-Capacitance Oscillator of Unusual Frequency Stability , 1948, Proceedings of the IRE.

[10]  Sebastian Stoecklin,et al.  Efficient Wireless Powering of Biomedical Sensor Systems for Multichannel Brain Implants , 2016, IEEE Transactions on Instrumentation and Measurement.

[11]  Kohji Koshiji,et al.  Development of electromagnetic phantom at low-frequency band , 2013, 2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC).

[12]  E. B. Rosa,et al.  Formulas and tables for the calculation of mutual and self-inductance (Revised) , 1912 .

[13]  Changzhi Li,et al.  Non-contact human machine interface based on bio-interaction with wireless power transfer features , 2015, 2015 IEEE MTT-S 2015 International Microwave Workshop Series on RF and Wireless Technologies for Biomedical and Healthcare Applications (IMWS-BIO).

[14]  Changzhan Gu,et al.  Non-contact hand interaction with smart phones using the wireless power transfer features , 2015, 2015 IEEE Radio and Wireless Symposium (RWS).

[15]  Jiang Long,et al.  Wireless Sensing System-on-Chip for Near-Field Monitoring of Analog and Switch Quantities , 2012, IEEE Transactions on Industrial Electronics.

[16]  Mark I. Montrose.  Printed Circuit Board Basics , 2000 .

[17]  Barry R. Eisenberg.  Frequency Stability of a Clapp VCO , 1969 .

[18]  Marian K. Kazimierczuk,et al.  Self-Capacitance of Coupled Toroidal Inductors for EMI Filters , 2015, IEEE Transactions on Electromagnetic Compatibility.

[19]  A. Peyton,et al.  Eddy current measurement of the electrical conductivity and porosity of metal foams , 2006, IEEE Transactions on Instrumentation and Measurement.

[20]  Steffen Leonhardt,et al.  Noncontact Monitoring of Cardiorespiratory Activity by Electromagnetic Coupling , 2013, IEEE Transactions on Biomedical Engineering.