Method of detecting and analyzing changes in the external loading conditions of a structure

• US 20060042396A1
• Filed: 08/26/2004
• Published: 03/02/2006
• Est. Priority Date: 08/26/2004
• Status: Active Grant

• Current Assignee: Acellent Technologies, Inc.
• Original Assignee: Acellent Technologies, Inc.
• Inventors: Qing, Xinlin, Li, Irene, Zhang, Chang
• Granted Patent: US 7,430,911 B2
• Time in Patent Office: Days
• US Class Current: 73/786
• CPC Class Codes: G01L 1/162 using piezoelectric resonators
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0041 by determining deflection or stress
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction

Abstract

A method for both detecting and analyzing a change in the loading condition of a structure. A flexible substrate is employed, in which a distributed network of sensors is built. This substrate is either affixed to the surface of the structure, or built within it, so as to be able to detect propagating stress waves. After load change is detected, the resulting sensor signals are analyzed to determine the location, severity, and/or any characteristic frequencies of the load change. This information is then used to determine an appropriate response.

Claims

1. A method of detecting and analyzing a change in the external loading condition of a structure, comprising:

receiving electrical signals from a plurality of sensors affixed to and spatially distributed on a flexible substrate attached to a structure, the sensors configured to generate the electrical signals upon detection of propagating stress waves generated by a load change at a location of the structure, the propagating stress waves having frequencies corresponding to a severity of the load change;

isolating those frequencies of the stress waves that fall within a range of frequencies, so as to facilitate detection of the load change;

analyzing the electrical signals so as to determine the location of the load change; and

processing the electrical signals so as to determine the severity of the load change.

2. The method of claim 1 further comprising initiating a response to the load change based upon the isolated frequencies;

the location of the load change, and the severity of the load change.

3. The method of claim 1 wherein the flexible substrate is attached to the structure so as to spatially distribute the sensors in an array, the array of sensors configured to detect propagating stress waves at various positions along the structure.

4. The method of claim 3 wherein the sensors are piezoelectric sensors.

5. The method of claim 3 wherein the analyzing further comprises calculating a total strain energy detected at each of the positions along the structure, and determining the location of the load change from each of the total strain energies and their respective positions along the structure.

6. The method of claim 3 wherein the analyzing further comprises, for each of the sensors, recording a time at which the propagating stress waves are detected, and determining the location from the times at which the propagating stress waves are detected by each of the sensors, and the respective positions of each of the sensors.

7. The method of claim 1 wherein the isolating further comprises filtering the electrical signals by engaging a low pass filter affixed to the flexible substrate, the low pass filter being configured to pass low frequencies of the electrical signals and to attenuate higher frequencies of the electrical signals, so as to isolate those frequencies of the load change that are among the lower frequencies.

8. The method of claim 7 wherein each of the sensors is electrically connected to a separate one of the low pass filters, and wherein each of the low pass filters comprises a resistor in electrical series with its associated sensor, and a capacitor in electrical parallel with its associated sensor and associated resistor.

9. The method of claim 1 wherein the isolating further comprises filtering the electrical signals by engaging a high pass filter affixed to the flexible substrate, the high pass filter being configured to pass high frequencies of the electrical signals and to attenuate lower frequencies of the electrical signals, so as to isolate those frequencies of the load change that are among the higher frequencies.

10. The method of claim 9 wherein each of the sensors is electrically connected to a separate one of the high pass filters, and wherein each of the high pass filters comprises a capacitor in electrical series with its associated sensor, and a resistor in electrical parallel with its associated sensor and associated capacitor.

11. The method of claim 1 wherein the isolating further comprises filtering the electrical signals by engaging a band pass filter configured to pass band frequencies of the electrical signals and to attenuate both those frequencies of the electrical signals that are higher than the band frequencies, and those frequencies of the electrical signals that are lower than the band frequencies, so as to isolate those frequencies of the load change that are among the band frequencies.

12. A method of detecting and analyzing a change in the external loading condition of a structure, comprising:

monitoring electrical signals emitted by a plurality of sensors affixed to and spatially distributed on a flexible substrate attached to a structure, the sensors configured to generate the electrical signals upon detection of propagating stress waves generated by a load change at a location of the structure, the propagating stress waves having frequencies corresponding to a severity of the load change;

isolating those frequencies of the stress waves that fall within a range of frequencies;

determining an occurrence of the load change based upon the isolated frequencies of the stress waves;

upon the occurrence of the load change, recording the electrical signals;

processing the recorded electrical signals so as to determine a total strain energy detected at each of the positions along the structure;

calculating the location from each of the total strain energies and their respective positions along the structure; and

analyzing the recorded electrical signals so as to determine the severity of the load change.

13. The method of claim 12 further comprising responding to the load change according to the calculated location of the load change and the severity of the load change.

14. The method of claim 12 wherein the flexible substrate is attached to the structure so as to spatially distribute the sensors in an array, wherein the recording further comprises recording electrical signals corresponding to the propagating stress waves detected at various positions along the structure.

15. The method of claim 14 wherein the sensors are piezoelectric sensors.

16. The method of claim 12 wherein the filtering further comprises filtering the electrical signals by engaging a low pass filter affixed to the flexible substrate, the low pass filter being configured to pass low frequencies of the electrical signals and to attenuate higher frequencies of the electrical signals, so as to isolate those frequencies of the load change that are among the lower frequencies.

17. The method of claim 16 wherein each of the sensors is electrically connected to a separate one of the low pass filters, and wherein each of the low pass filters comprises a resistor in electrical series with its associated sensor, and a capacitor in electrical parallel with its associated sensor and associated resistor.

18. The method of claim 12 wherein the filtering further comprises filtering the electrical signals by engaging a high pass filter affixed to the flexible substrate, the high pass filter being configured to pass higher frequencies of the electrical signals and to attenuate lower frequencies of the electrical signals, so as to isolate those frequencies of the load change that are among the higher frequencies.

19. The method of claim 18 wherein each of the sensors is electrically connected to a separate one of the high pass filters, and wherein each of the high pass filters comprises a capacitor in electrical series with its associated sensor, and a resistor in electrical parallel with its associated sensor and associated capacitor.

20. The method of claim 12 wherein the filtering further comprises filtering the electrical signals by engaging a band pass filter affixed to the flexible substrate, the band pass filter being configured to pass band frequencies of the electrical signals and to attenuate both those frequencies of the electrical signals that are higher than the band frequencies, and those frequencies of the electrical signals that are lower than the band frequencies, so as to isolate those frequencies of the load change that are among the band frequencies.

21. A computer readable memory to direct a computer to function in a specified manner, comprising:

a first module to monitor electrical signals emitted by a plurality of sensors affixed to and spatially distributed on a flexible substrate attached to a structure, the sensors configured to generate the electrical signals upon detection of propagating stress waves generated by a load change at a location of the structure, the propagating stress waves having frequencies corresponding to a severity of the load change;

a second module to determine, according to isolated ones of the frequencies that fall within a range of frequencies, an occurrence of the load change;

a third module to record the electrical signals upon the occurrence of the load change;

a fourth module to process the recorded electrical signals so as to determine a total strain energy detected at each of the positions along the structure;

a fifth module to calculate the location from each of the total strain energies and their respective positions along the structure; and

a sixth module to analyze the recorded electrical signals so as to determine the severity of the load change.

22. The computer readable memory of claim 21 further comprising a seventh module to respond to the load change according to the calculated location of the load change and the severity of the load change.

23. The computer readable memory of claim 21 further comprising an eighth module to filter the electrical signals so as to isolate those frequencies of the load change that fall within the range of frequencies.