Systems and methods of generating diagnostic images for structural health monitoring

• US 20070260425A1
• Filed: 07/10/2007
• Published: 11/08/2007
• Est. Priority Date: 09/22/2003
• Status: Abandoned Application

• Current Assignee: Advanced Structure Monitoring, Inc.
• Original Assignee: Advanced Monitoring Systems, Inc.
• Inventors: Kim, Hyeung-Yun
• Application Number:
  US11/827,415
• Publication Number:
  US 20070260425A1
• Time in Patent Office: Days
• US Class Current: 702/182
• CPC Class Codes: G01H 11/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01M 11/086 Details about the embedment of the optical fiber within the DUT
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/02491 Materials with nonlinear acoustic properties
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 29/043 in the interior, e.g. by shear waves
• CPC Class Codes: G01N 29/0609 Display arrangements, e.g. colour displays indicating or recording in connection with measuring in general G01D
• CPC Class Codes: G01N 29/0672 by acoustic tomography medical tomography A61B8/13
• CPC Class Codes: G01N 29/07 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/245 : Ceramic probes, e.g. lead zirconate titanate [PZT] probes
• CPC Class Codes: G01N 29/2475 : Embedded probes, i.e. probes incorporated in objects to be inspected
• CPC Class Codes: G01N 29/2493 : Wheel shaped probes
• CPC Class Codes: G01N 29/28 : providing acoustic coupling , e.g. water impedance matching G10K11/02
• CPC Class Codes: G01N 29/4418 : with a model, e.g. best-fit, regression analysis
• CPC Class Codes: G01N 29/4463 : Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering

Abstract

Systems, methods and recordable media for determining damage index values associated with paths in a network having a plurality of diagnostic network patches (DNP). A method includes the steps of selecting first and second patches to define a path therebetween; causing the first patch to transmit a signal along the path and the second patch to receive the signal; processing the signal received by the second patch to determine a damage index value that is a quantity to be affected by damage in a host structure of the network; and associating the damage index value with the path.

Claims

1. A computer-implemented method of determining damage index values associated with paths in a network having a plurality of diagnostic network patches

(DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, the method comprising:

(a) selecting first and second ones from the patches to define a path therebetween;

(b) causing, by use of a computer processor, the first patch to transmit a signal along the path and the second patch to receive the signal;

(c) processing the signal received by the second patch to determine a damage index value that is a quantity to be affected by damage in a host structure of the network; and

(d) associating the damage index value with the path.

2. The method of claim 1, wherein the step of processing the signal includes:

filtering out an interference signal in the signal; and

detrending the signal to remove a nonstationary signal component.

3. The method of claim 1, wherein the step of processing the signal includes:

building an envelope window for the signal;

breaking the envelope window into one or more sub envelope windows; and

applying the sub envelope windows to extract wave packets from the signal, each of the wave packets corresponding to a wave mode.

4. The method of claim 3, wherein the wave mode is a fundamental symmetric mode S₀, a reflected mode S_ref—

₀, a fundamental antisymmetric mode A₀, or a basic shear mode S_H of a Lamb-wave.

5. The method of claim 3, wherein the step of building an envelope window for the signal is performed by use of a hill-climbing algorithm.

6. The method of claim 3, wherein the damage index value is a parameter of one of the sub envelop windows or the change in the parameter compared to a corresponding parameter of a baseline signal.

7. The method of claim 6, wherein the parameter is one selected from the group consisting of a maximum value, a center position, and a span width of one of the sub envelop windows.

8. The method of claim 3, wherein the step of processing the signal includes:

determining an energy of one of the wave packets.

9. The method of claim 8, wherein the damage index value is the energy or a change in the energy compared to a corresponding energy of a baseline signal.

10. The method of claim 8, wherein the damage index value is a sum of the energies of the wave packets or a change in the sum compared to a corresponding sum of a baseline signal.

11. The method of claim 3, wherein the step of processing the signal includes:

obtaining a time-frequency energy distribution of the signal by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining a time-of-arrival of the wave mode by use of the time-frequency energy distribution,

wherein the damage index value is the time-of-arrival or a change in the time-of arrival compared to a corresponding time-of-arrival of a baseline signal.

12. The method of claim 11, further comprising:

utilizing a dispersion curve formula to determine the time of arrival.

13. The method of claim 1, further comprising:

obtaining a plurality of time-frequency energy distributions, wherein each of the time-frequency energy distributions is obtained by performing a transformation of the signal obtained at an excitation frequency, the transformation being a short-time Fourier transformation or a wavelet transformation;

extracting ridge curves from the time-frequency energy distributions, the ridge curves representing a trajectory of a wave mode; and

determining the time-of-arrival by use of the ridge curves,

wherein the damage index value is the time-of-arrival or a change in the time-of arrival compared to a corresponding time-of-arrival of a baseline signal.

14. The method of claim 1, further comprising:

obtaining a time-frequency energy distribution of the signal by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining an energy using the time-frequency energy distribution,

wherein the damage index value is the energy or a change in the energy compared to a corresponding energy of a baseline signal.

15. The method of claim 1, further comprising:

decomposing the signal into one or more sub-bandwidth signals by use of a wavelet decomposition filter;

synthesizing a signal by combining one or more of the sub-bandwidth signals thereby the synthesized signal has a frequency bandwidth of interest;

building an envelope window for the synthetic signal;

breaking the envelope window into one or more sub envelope windows;

applying the sub envelope windows to extract wave packets from the synthesized signal; and

determining an energy of each of the wave packets.

16. The method of claim 15, wherein the damage index value is the energy of one of the wave packets or a change in the energy compared to a corresponding energy of a baseline signal.

17. The method of claim 15, wherein the damage index value is a sum of the energies of the wave packets or a change in the sum compared to a corresponding sum of a baseline signal.

18. The method of claim 1, further comprising:

removing abnormal signals.

19. The method of claim 18, wherein the step of removing abnormal signals includes:

repeating the steps (a)-(b) to obtain a set of signals received by the patches;

determining a discrete probability density function (DPDF) for the set of signals;

calculating a normality constant by use of a covariance, a skewness factor and a flatness factor of the DPDF;

determining, by use of the normality constant, if each of the set of signals is an abnormal signal; and

removing abnormal signals from the set of signals.

20. The method of claim 1, further comprising:

deleting outlier damage index values.

21. The method of claim 20, wherein the step of deleting outlier damage index values includes:

repeating the steps (a)-(c) to obtain a set of damage index values;

computing a probability density function (PDF) for the set of damage index values; and

deleting, based on the PDF, outlier damage index values that are outside a preset range in a distribution of the set of damage index values.

22. The method of claim 1, further comprising:

compensating for a difference between an ambient temperature for a baseline signal and an ambient temperature where the step (b) is performed.

23. The method of claim 22, wherein the step of compensating for a difference includes:

measuring the difference;

building a temperature reference table;

calculating a temperature-adjustment parameter using the table and the difference; and

scaling the damage index value with the parameter.

24. A computer-implemented method of determining damage index values in a network having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, the method comprising:

causing, by use of a computer processor, one or more of the patches to measure vibrational signals; and

computing structural dynamic parameters by use of the vibrational signals; and

utilizing the structural dynamic parameters as damage index values at locations of the patches.

25. The method of claim 24, wherein each of the patches is one selected from the group consisting of an accelerometer, a displacement transducer, and a strain gage.

26. The method of claim 24, wherein each of the parameters is at least one of a natural frequency, a damping ratio, and a mode shape.

27. A computer-implemented method of determining damage index values in a network having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, the method comprising:

causing, by use of a computer processor, one or more of the patches to receive signals in response to an impact on a host structure of the network; and

processing the signals to determine damage index values.

28. The method of claim 27, wherein the step of processing the signals includes:

filtering out an interference signal in each of the signals; and

detrending each of the signals to remove a nonstationary signal component.

29. The method of claim 27, wherein the step of processing the signals includes:

building an envelope window for each of the signals;

breaking the envelope window into one or more sub envelope windows; and

applying the sub envelope windows to extract wave packets from each of the signals, each of the wave packets corresponding to a wave mode.

30. The method of claim 29, wherein the step of processing the signals includes:

determining an energy of one of the wave packets.

31. The method of claim 30, wherein each of the damage index values is the energy or a change in the energy compared to a corresponding energy of a baseline signal.

32. The method of claim 30, wherein each of the damage index values is a sum of the energies of the wave packets or a change in the sum compared to a corresponding sum of a baseline signal.

33. The method of claim 29, wherein the step of processing the signals includes:

obtaining a time-frequency energy distribution of each of the signals by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining a time-of-arrival of the wave mode by use of the time-frequency energy distribution,

wherein each of the damage index values is the time-of-arrival or a change in the time-of-arrival compared to a corresponding time-of-arrival of a baseline signal.

34. The method of claim 27, further comprising:

obtaining a time-frequency energy distribution of each of the signals by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining an energy using the time-frequency energy distribution,

wherein each of the damage index values is the energy or a change in the energy compared to a corresponding energy of a baseline signal.

35. The method of claim 27, further comprising:

decomposing each of the signals into one or more sub-bandwidth signals by use of a wavelet decomposition filter;

synthesizing a signal by combining one or more of the sub-bandwidth signals thereby the synthesized signal has a frequency bandwidth of interest;

building an envelope window for the synthetic signal;

breaking the envelope window into one or more sub envelope windows;

applying the sub envelope windows to extract wave packets from the synthesized signal; and

determining an energy of each of the wave packets.

36. The method of claim 35, wherein each of the damage index values is the energy of one of the wave packets or a change in the energy compared to a corresponding energy of a baseline signal.

37. The method of claim 35, wherein each of the damage index values is a sum of the energies of the wave packets or a change in the sum compared to a corresponding sum of a baseline signal.

38. The method of claim 27, further comprising:

compensating for a difference between an ambient temperature for a baseline signal and an ambient temperature where the step of causing one or more of the patches to receive signals is performed.

39. The method of claim 38, further comprising:

measuring the difference;

building a temperature reference table;

calculating a temperature-adjustment parameter using the table and the difference; and

scaling each of the damage index values with the parameter.

40. A computer readable medium carrying one or more sequences of instructions for determining damage index values associated with paths in a network having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:

selecting first and second ones from the patches to define a path therebetween;

causing, by use of a computer processor, the first patch to transmit a signal along the path and the second patch to receive the signal;

processing the signal received by the second patch to determine a damage index value that is a quantity to be affected by damage in a host structure of the network; and

associating the damage index value with the path.

41. The computer readable medium of claim 40, wherein the step of processing the signal includes:

building an envelope window for the signal;

breaking the envelope window into one or more sub envelope windows; and

applying the sub envelope windows to extract wave packets from the signal, each of the wave packets corresponding to a wave mode.

42. The computer readable medium of claim 40, wherein the step of processing the signal further includes:

obtaining a time-frequency energy distribution of the signal by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining a time-of-arrival of the wave mode by use of the time-frequency energy distribution.

43. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional steps of:

obtaining a plurality of time-frequency energy distributions, wherein each of the time-frequency energy distributions is obtained by performing a transformation of the signal obtained at an excitation frequency, the transformation being a short-time Fourier transformation or a wavelet transformation;

extracting ridge curves from the time-frequency energy distributions, the ridge curves representing a trajectory of a wave mode; and

determining the time-of-arrival by use of the ridge curves.

44. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional steps of:

obtaining a time-frequency energy distribution of the signal by use of a transformation, wherein the transformation is a short-time Fourier transformation or a wavelet transformation; and

determining a spectrum energy using the time-frequency energy distribution.

45. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional steps of

decomposing the signal into one or more sub-bandwidth signals by use of a wavelet decomposition filter;

synthesizing a signal by combining one or more of the sub-bandwidth signals thereby the synthesized signal has a frequency bandwidth of interest;

building an envelope window for the synthetic signal;

breaking the envelope window into one or more sub envelope windows;

applying the sub envelope windows to extract wave packets from the synthesized signal; and

determining a spectrum energy of each of the wave packets.

46. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional step of:

removing abnormal signals.

47. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional step of:

deleting outlier damage index values.

48. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional step of:

compensating for a difference between an ambient temperature for a baseline signal and an ambient temperature where the step of causing the first patch to transmit a signal is performed.

49. The computer readable medium of claim 40, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the additional step of:

converting the signal received by the second patch into an eXtensible Markup Language (XML) formatted document.

50. The computer readable medium of claim 40, wherein the one or more sequences of instructions implement a wireless communication method of Wireless Application Protocol (WAP) or Wireless Markup Language (WML) for the Internet Web Access of a WAP-enable cell phone, Pocket PC with a HTML browser, or other HTML enable devices.

51. A computer readable medium carrying one or more sequences of instructions for determining damage index values in a network having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:

causing, by use of a computer processor, the patches to measure vibrational signals; and

computing structural dynamic parameters by use of the vibrational signals; and

utilizing the structural dynamic parameters as damage index values at locations of the patches.

52. A computer readable medium carrying one or more sequences of instructions for determining damage index values in a network having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch, wherein execution of one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:

causing, by use of a computer processor, one or more of the patches to receive signals in response to an impact on a host structure of the network; and

processing the signals to determine damage index values.

53. A system for monitoring a health condition of a host structure, comprising:

a network to be coupled to a host structure and having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch;

means for selecting first and second ones from the patches to define a path therebetween;

means for causing, by use of a computer processor, the first patch to transmit a signal along the path and the second patch to receive the signal;

means for processing the signal received by the second patch to determine a damage index value that is a quantity to be affected by damage in a host structure of the network; and

means for associating the damage index value with the path.

54. The system of claim 53, wherein the means for processing the signal includes:

means for building an envelope window for the signal;

means for breaking the envelope window into one or more sub envelope windows; and

means for applying the sub envelope windows to extract wave packets from the signal, each of the wave packets corresponding to a wave mode.

55. A system for monitoring a health condition of a host structure, comprising:

a network to be coupled to a host structure and having a plurality of diagnostic network patches (DNP), each of the patches being able to operate as at least one of a transmitter patch and a sensor patch;

means for causing, by use of a computer processor, one or more of the patches to receive signals in response to an impact on a host structure of the network; and

means for processing the signals to determine damage index values.