Resistive-capacitive deformation sensor

Patent metadata

Field	Value
Publication number	US-10067007-B2
Application number	US-201514843067-A
Country	US
Kind code	B2
Filing date	Sep 2, 2015
Priority date	Sep 2, 2015
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

A deformation sensing apparatus comprises an elastic substrate, a first strain-gauge element formed on a first surface of the elastic substrate, and configured to output a first signal in response to a strain applied in a first direction, and a second strain-gauge element formed on a second surface of the elastic substrate opposite to the first surface, and configured to output a second signal in response to a strain applied in the same first direction.

First claim

What is claimed is:

1. A deformation sensing apparatus comprising:
an elastic substrate;
a first strain-gauge element having two distinct terminals comprising a first terminal and a second terminal, wherein the first strain-gauge element is formed on a top surface of the elastic substrate and is configured to output a first signal in response to a strain applied in a first direction, the first signal measurable across the first and second terminals of the first strain-gauge element; and
a second strain-gauge element having two distinct terminals comprising a third terminal and a fourth terminal, wherein the second strain-gauge element is formed on a bottom surface of the elastic substrate opposite to the top surface and is configured to output a second signal in response to a strain applied in the same first direction, the second signal measurable across the third and fourth terminals of the second strain-gauge element.

2. The deformation sensing apparatus of claim 1 , wherein:
the elastic substrate comprises a flexible, electrically-insulating dielectric material; and
the deformation sensing apparatus is configured to output a third signal responsive to an applied deformation, the third signal being measurable between a terminal of the first strain-gauge element and a terminal of the second strain-gauge element.

3. The deformation sensing apparatus of claim 2 , further comprising:
a measurement circuit configured to measure the first signal from the first strain-gauge element and the second signal from the second strain-gauge element in response to the applied deformation; and
a deformation analyzer configured to compute a measure of stretch deformation and a measure of flex deformation of the sensing apparatus, in the applied deformation, based on the measured first signal from the first strain-gauge element, the measured second signal of the second strain-gauge element, and the third signal.

4. The deformation sensing apparatus of claim 3 , wherein:
the first signal is indicative of a first resistance of the first strain-gauge element;
the second signal is indicative of a second resistance of the second strain-gauge element; and
the third signal is indicative of a capacitance across the elastic substrate measured responsive to the applied deformation.

5. The deformation sensing apparatus of claim 4 , wherein the deformation analyzer computes the measure of stretch deformation as a proportion of length change ((ΔL)/L 0 ) of the first and second strain-gauge elements, based on the first, second, and third signals, using the equations:
R 1 =R 2 =R 0 +(GF·Δ L )

C
=

ɛ
⁢

Area
gap

=

ɛ
⁢

L
0

-

W
0

g

=

ɛ
⁢

L
0

-

W
0

(

g
0

-

Δ
⁢

⁢
L

-
Y

)

=

ɛ
⁢

L
0

·

W
0

(

g
0

-

(

Δ
⁢

⁢

L
1

+

Δ
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L
2

2

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,

where R 1 is the first resistance, R 2 is the second resistance, C is the capacitance, and
Area is an overlap between first and second strain-gauge elements,
GF is a Gauge Factor relating strain and resistance,
γ is a Poisson's Ratio of the elastic substrate relating deformations between axes,
L 0 is an undeformed length of the first and second strain-gauge elements,
ΔL, Δ L1 , ΔL 2 are length changes of the first and second strain-gauge elements,
W 0 is an undeformed length of the first and second strain-gauge elements,
c is a dielectric constant of the elastic substrate,
R 0 is a baseline resistance of the first and second strain-gauge elements, and
g, g 0 are, respectively, deformed and baseline widths of the elastic substrate.

Assignees

• Oculus Vr Llc

Inventors

• Keller Sean Jason
• Trutna Tristan Thomas
• Perek David R
• Cleary Iii Bruce A

Classifications

• G01L1/20

  by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids (of piezo-resistive materials G01L1/18); by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress · CPC title

• G01B7/22

  using change in capacitance · CPC title

• G01B7/18

  using change in resistance · CPC title

• G01L15/00 Primary

  Devices or apparatus for measuring two or more fluid pressure values simultaneously · CPC title

• G01L1/142 Primary

  using capacitors · CPC title