STRUCTURAL HEALTH MONITORING SENSOR SYSTEM AND METHOD USING RESONANT TRANSMISSION LINE SENSORS

• US 20090009188A1
• Filed: 07/06/2007
• Published: 01/08/2009
• Est. Priority Date: 07/06/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Gualtieri, Devlin M.
• Granted Patent: US 7,888,950 B2
• Time in Patent Office: Days
• US Class Current: 324/633
• CPC Class Codes: G01M 5/0025 of elongated objects, e.g. pipes, masts, towers or railways G01M5/0058 takes precedence
• CPC Class Codes: G01M 5/0041 by determining deflection or stress
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection

Abstract

A structural health monitoring system and method uses a resonant transmission line sensor. A resonant transmission line sensor, which includes one or more sensor conductors and a dielectric material disposed at least proximate the one or more sensor conductors, is coupled to the structure. The dielectric material exhibits a dielectric constant that varies when at least a portion of the transmission line sensor is subjected to one or more stimuli. One or more resonant frequencies of the transmission line sensor are determined, and the determined one or more resonant frequencies are then correlated to the structural health of the structure.

Claims

1. A structural health monitoring sensor system, comprising:

a variable frequency signal source operable to supply one or more sensor drive signals at one or more frequencies;

a transmission line sensor having one or more resonant frequencies, the transmission line sensor including one or more sensor conductors and a dielectric material disposed at least proximate the one or more sensor conductors, the transmission line sensor having a driven end coupled to receive the one or more sensor drive signals and a terminal end configured to reflect the one or more sensor drive signals to thereby supply one or more reflected signals to the driven end, the dielectric material exhibiting a dielectric constant that varies when at least a portion of the transmission line sensor is subjected to one or more stimuli;

a summing circuit coupled to receive the one or more sensor drive signals and the one or more reflected signals and operable, in response thereto, to supply one or more standing wave signals having amplitudes that vary with the one or more resonant frequencies of the transmission line sensor; and

a monitor circuit coupled to receive the one or more standing wave signals and operable, in response thereto, to determine one or more resonant frequencies of the transmission line sensor.

2. The sensor system of claim 1, wherein the variable frequency source is configured to continuously supply a sensor drive signal.

3. The sensor system of claim 2, wherein:

the monitor circuit is further coupled to receive the standing wave signal and is further operable, in response thereto, to (i) determine the sensor drive signal frequency relative to at least one of the transmission line sensor resonant frequencies and (ii) supply the frequency control signal to the variable frequency source, to thereby adjust the sensor drive signal frequency to substantially match at least one of the transmission line sensor one or more resonant frequencies.

4. The sensor system of claim 3, wherein:

the monitor circuit is further coupled to receive the adjusted sensor drive signal and is further operable, in response thereto, to supply a signal representative of the one or more stimuli to which the transmission line sensor is being subjected.

5. The sensor system of claim 1, wherein the one or more stimuli include variations in one or more mechanical states.

6. The sensor system of claim 1, wherein the one or more mechanical states include one or more of stress, strain, and structural integrity.

7. The sensor system of claim 1, wherein the one or more stimuli include variations of an environmental condition.

8. The sensor system of claim 7, wherein the environmental condition includes one or more of temperature, chemical exposure, and radiation exposure.

9. The sensor system of claim 1, wherein the stimulus is a variation in mechanical state, a variation of an environmental condition, or both.

10. The sensor system of claim 1, wherein:

the mechanical state includes one or more of stress, strain, and structural integrity; and

the environmental condition includes one or more of temperature, chemical exposure, and radiation exposure.

11. The sensor system of claim 1, wherein:

the sensor is coupled to a structure; and

the dielectric material forms at least part of the structure.

17. The method of claim 1, wherein the one or more stimuli include variations of an environmental condition.

18. The method of claim 17, wherein the environmental condition includes one or more of temperature, chemical exposure, and radiation exposure.

12. A method of monitoring structural health of a structure, comprising the steps of:

coupling a resonant transmission line sensor to the structure, the transmission line sensor including one or more sensor conductors and a dielectric material disposed at least proximate the one or more sensor conductors, the dielectric material exhibiting a dielectric constant that varies when at least a portion of the transmission line sensor is subjected to one or more stimuli;

determining one or more resonant frequencies of the transmission line sensor; and

correlating the determined one or more resonant frequencies to the structural health of the structure.

13. The method of claim 12, further comprising:

supplying one or more sensor drive signals at one or more frequencies to the resonant transmission line sensor.

14. The method of claim 13, wherein the resonant transmission line sensor is configured, upon receipt of the one or more sensor drive signals, to supply one or more reflected signals, and wherein the method further comprises:

determining the one or more resonant frequencies of the transmission line sensor in part from the one or more reflected signals.

15. The method of claim 12, wherein the one or more stimuli include variations in one or more mechanical states.

16. The method of claim 12, wherein the one or more mechanical states include one or more of stress, strain, and structural integrity.

19. The method of claim 12, wherein the stimulus is a variation in mechanical state, a variation of an environmental condition, or both.

20. The method of claim 12 wherein:

the mechanical state includes one or more of stress, strain, and structural integrity; and

the environmental condition includes one or more of temperature, chemical exposure, and radiation exposure.