Wearable inductive-force sensor

• US 10,386,249 B2
• Filed: 02/20/2015
• Issued: 08/20/2019
• Est. Priority Date: 02/20/2014
• Status: Active Grant

• Current Assignee: University of Akron
• Original Assignee: University of Akron
• Inventors: Zhe, Jiang, Du, Li
• Primary Examiner(s): Abouelela, May A
• Application Number:
  US14/627,494
• Publication Number:
  US 20150233776A1
• Time in Patent Office: 1,642 Days
• Field of Search: 600300, 600301, 600587, 600592, 7386269
• CPC Class Codes: A61B 2562/164 the sensor is mounted in or on a conformable substrate or carrier
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/1038 Measuring plantar pressure during gait
• CPC Class Codes: A61B 5/6807 Footwear
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence

Abstract

A wearable inductive-force sensor, which provides high-sensitivity dynamic measurements of both normal force and shear force, utilizes three spiral planar force sensing coils. These spiral planar coils allow the measurement of shear force in the x and y directions and the measurement of a normal force in the z direction. The force sensor is configured to be mounted in various locations, such as an insole of a shoe, so as to provide real-time force sensing of forces that are applied to a patient'"'"'s feet as they move. In addition, force-measurement electronics used with the force sensor are configured to use resonance-frequency division signal multiplexing to monitor the response of the force sensing coils, which allows the sensor to have minimal complexity, while still being highly sensitive.

Claims

1. A force sensor comprising:

a substrate;

a first, second and third coil disposed on said substrate each adapted to generate an initial magnetic field upon receipt of an A.C. (alternating current) signal;

a capacitor coupled in parallel with each one of said coils;

an electrically conductive section supported by a section of flexible material, wherein said flexible material is attached to said substrate, such that said electrically conductive section is spaced from said coils, whereby one of said initial magnetic fields forms one or more corresponding induced magnetic fields in said electrically conductive section;

wherein upon an application of a force to the sensor, at least one of said substrate and said electrically conductive section moves, such that a position of one or more said coils relative to said electrically conductive section is changed, whereby one or more of said induced magnetic fields are detected by one or more of said coils, so as to change a magnitude of inductance of one or more of said coils, with each said change in magnitude of inductance being associated with a measurement of the application of force; and

wherein said electrically conductive section has an edge that passes through a center of said first and second coils.

2. The force sensor of claim 1, further comprising an insole of a shoe that includes said coils.

3. The force sensor of claim 1, wherein said substrate comprises a dielectric material.

4. The force sensor of claim 1, wherein said coils comprise spiral-wound coils.

5. The force sensor of claim 4, wherein said spiral-wound coils comprise planar coils.

6. The force sensor of claim 5, wherein said spiral-wound planar coils comprise a plurality of turns.

7. The force sensor of claim 1, wherein said section of flexible material is formed of rubber.

8. The force sensor of claim 1, wherein said electrically conductive section comprises stainless steel.

9. The force sensor of claim 1, further comprising:

a force-measurement device coupled to said first, second and third coils, wherein said force-measurement device is configured to measure an amount of movement of said electrically conductive section relative to said coils, so as to calculate therefrom the measurement of the application of the force.

10. The force sensor of claim 9, wherein said force-measurement device comprises:

a resistor coupled in series with said first, second and third coils;

an A.C. (alternating current) signal generator that is coupled in series with said resistor; and

a data acquisition unit coupled in parallel with said first, second and third coils;

wherein said A.C. signal generator generates a combined signal, which includes a plurality of signals each having a resonant frequency associated with said first, second and third coils respectively, such that said data acquisition unit monitors said first, second and third coils to identify the amount of force applied to the sensor.

11. The force sensor of claim 9, wherein said force-measurement device includes a communication interface to transfer the calculated amount of force to a remote computer.

12. The force sensor of claim 9, wherein said force-measurement device calculates the amount of force in real-time.

13. The force sensor of claim 1, further comprising:

a controller configured to identify the change in magnitude of said magnetic field of one or more of said coils to generate therefrom a measurement of one or more forces applied to the sensor.

14. The force sensor of claim 1, wherein said electrically conductive section covers said third coil.

15. The force sensor of claim 1, wherein said substrate comprises an insole.

16. The force sensor comprising:

a substrate;

a first, second and third coil disposed on said substrate each adapted to generate an initial magnetic field upon receipt of an A.C. (alternating current) signal;

a capacitor coupled in parallel with each one of said coils;

an electrically conductive section supported by a section of flexible material, wherein said flexible material is attached to said substrate, such that said electrically conductive section is spaced from said coils, whereby one of said initial magnetic fields forms one or more corresponding induced magnetic fields in said electrically conductive section, and wherein said section of flexible material comprises a plurality of individual sections of flexible material; and

a cover plate that is supported by said plurality of individual sections of flexible material, with said electrically conductive section being attached to said cover plate, wherein upon an application of a force to the sensor, at least one of said substrate and said electrically conductive section moves, such that a position of one or more said coils relative to said electrically conductive section is changed,

whereby one or more of said induced magnetic fields are detected by one or more of said coils, so as to change a magnitude of inductance of one or more of said coils, with each said change in magnitude of inductance being associated with a measurement of the application of force.