Non-invasive thickness measurement using fixed frequency

Patent metadata

Field	Value
Publication number	US-11060841-B2
Application number	US-201816086147-A
Country	US
Kind code	B2
Filing date	May 29, 2018
Priority date	Jun 5, 2017
Publication date	Jul 13, 2021
Grant date	Jul 13, 2021

Abstract

A method of measuring thickness of a material generally includes applying an oscillating signal to a first electrode at a fixed frequency, passing the signal through the material to a second electrode, and measuring the magnitude of the signal reflected back to the first electrode. The thickness of the material is determined based on the measured magnitude of the reflected signal by: 1) comparing the determined magnitude to a predetermined baseline to establish a difference; and 2) identifying the thickness based on the difference. Related apparatuses are also disclosed. The material may be a vehicle tire.

First claim

What is claimed is:

1. A method of determining a thickness of a material, the method comprising:
applying an oscillating transmit signal to a first electrode affixed to the material;
wherein the transmit signal is applied at a fixed frequency;

passing the transmit signal through the material;
reflecting the transmit signal at a second electrode after the transmit signal has passed through the material, the second electrode disposed in spaced relation to the first electrode and electrically isolated therefrom; the second electrode affixed to the material; wherein the first and second electrodes are disposed on a same side of the material;
receiving the reflected signal at the first electrode; wherein the reflected signal is oscillating at the fixed frequency;
measuring a magnitude of the reflected signal at the fixed frequency;
determining the thickness of the material based on the measured magnitude by:
comparing the determined magnitude to a predefined baseline value to establish a difference, the predefined baseline value corresponding to an initial thickness of the material and being established before the applying the oscillating signal to the first electrode; and
identifying the thickness based on the difference.

2. The method of claim 1 , further comprising determining the fixed frequency prior to the applying the oscillating signal.

3. The method of claim 2 , wherein the determining the fixed frequency comprises:
transmitting a sweep signal from the first electrode sweeping a frequency band while a frequency of the sweep signal is varied over time so that the signal is transmitted at a plurality of frequencies in corresponding time intervals;
determining a resonant frequency based on a reflection of the sweep signal by the second electrode;
setting the fixed frequency as being within 20% of the determined resonant frequency.

4. The method of claim 3 , wherein the setting the fixed frequency comprises setting the fixed frequency to be less than the determined resonant frequency.

5. The method of claim 1 , wherein the first electrode and the second electrode are disposed substantially parallel to each other.

6. The method of claim 1 , wherein the identifying the thickness comprises using the difference to reference a look-up table of stored values.

7. The method of claim 1 , wherein the identifying the thickness comprises calculating the thickness based on the difference and a stored predefined value.

8. The method of claim 1 , wherein the material comprises metal embedded in a dielectric material.

9. The method of claim 8 , wherein the material comprises a portion of a vehicle tire.

10. The method of claim 9 , wherein the metal comprises a steel reinforcing mesh for the vehicle tire.

11. The method of claim 1 , wherein the fixed frequency is in the range 300 MHz to 900 MHz.

12. The method of claim 11 , wherein the fixed frequency is in the range 477 MHz to 487 MHz.

13. A measurement system for determining a thickness of a material, the system comprising:
a first electrode;
a second electrode;
processing circuitry operatively connected to the first electrode; wherein the processing circuitry is configured to:
apply an oscillating transmit signal at a fixed frequency to the first electrode while the first electrode is affixed to the material, to thereby cause the transmit signal to pass through the material and be reflected at the second electrode as a reflected signal; wherein the first and second electrodes are disposed on a same side of the material;
process the reflected signal received at the first electrode to measure a magnitude of the reflected signal at the fixed frequency; wherein the reflected signal is oscillating at the fixed frequency;
determine the thickness of the material based on the measured magnitude by:
comparing the determined magnitude to a predefined baseline value to establish a difference, the predefined baseline value corresponding to an initial thickness of the material and being established before the oscillating signal to the first electrode; and
identifying the thickness based on the difference;

wherein the second electrode is affixed to the material and disposed in spaced relation to the first electrode and electrically isolated therefrom during the reflection.

14. The measurement system of claim 13 , wherein the processing circuitry is configured to determine the fixed frequency prior to the applying the oscillating signal.

15. The measurement system of claim 14 , wherein the processing circuitry is configured to determine the fixed frequency by:
transmitting a sweep signal from the first electrode sweeping a frequency band while a frequency of the sweep signal is varied over time so that the signal is transmitted at a plurality of frequencies in corresponding time intervals;
determining a resonant frequency based on a reflection of the sweep signal by the second electrode;
setting the fixed frequency as being within 20% of the determined resonant frequency.

16. The measurement system of claim 13 , wherein the processing circuitry is configured to identify the thickness using the difference to reference a look-up table of stored values.

17. The measurement system of claim 13 , wherein the processing circuitry is configured to identify the thickness by at least one of:
calculating the thickness based on the difference and a stored predefined value; and
using the difference to reference a look-up table of stored values.

18. The measurement system of claim 13 , wherein the fixed frequency is in the range 300 MHz to 900 MHz.

19. The measurement system of claim 18 , wherein the fixed frequency is in the range 477 MHz to 487 MHz.

20. A tire assembly, comprising:
a tire comprising a dielectric material and a metal material embedded therein; the tire having an inner surface and an exterior surface disposed generally opposite to the inner surface;
a first electrode affixed to the inner surface;
a second electrode affixed to the inner surface and disposed in spaced relation to the first electrode and electrically isolated therefrom;
processing circuitry communicatively connected to the first electrode and configured to:
apply an oscillating transmit signal at a fixed frequency to the first electrode, to thereby cause the transmit signal to pass through the material and be reflected at the second electrode as a reflected signal; material; wherein the first and second electrodes are disposed on a same side of the material;

process the reflected signal received at the first electrode to measure a magnitude of the reflected signal at the fixed frequency; wherein the reflected signal is oscillating at the fixed frequency;
determine the thickness of the material based on the measured magnitude by:
comparing the determined magnitude to a predefined baseline value to establish a difference, the predefined baseline value corresponding to an initial thickness of the material and being established before the transmit signal is applied to the first electrode; and
identifying the thickness based on the difference.

Assignees

• Univ Duke

Inventors

• Andrews Joseph Batton
• Brooke Martin
• Franklin Aaron

Classifications

• G01B7/06 Primary

  for measuring thickness {(measuring during the manufacture of coatings C23C14/54)} · CPC title

• B60C25/0551

  mechanical · CPC title

• G01B15/02

  for measuring thickness · CPC title

• B60C25/007

  outside surface (measuring profile depth G01B11/22) · CPC title

• B60C2019/004

  Tyre sensors other than for detecting tyre pressure · CPC title