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Defect Pattern Recognition by Sensor Data Fusion in the "Coin Tap Test" Huadong Wu, Mel Siegel The Robotics Institute, SCS Carnegie Mellon University.

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Presentation on theme: "Defect Pattern Recognition by Sensor Data Fusion in the "Coin Tap Test" Huadong Wu, Mel Siegel The Robotics Institute, SCS Carnegie Mellon University."— Presentation transcript:

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2 Defect Pattern Recognition by Sensor Data Fusion in the "Coin Tap Test" Huadong Wu, Mel Siegel The Robotics Institute, SCS Carnegie Mellon University The Robotics Institute, SCS Carnegie Mellon University

3 Conclusion force-time waveform is a good indicator of whether an impact is appropriate or notforce-time waveform is a good indicator of whether an impact is appropriate or not it also tells when free-vibration beginsit also tells when free-vibration begins free-vibration sound is the best indicator of substrate conditions — especially shallow delamination conditionsfree-vibration sound is the best indicator of substrate conditions — especially shallow delamination conditions

4 Introduction coin-tap testcoin-tap test aircraft skin inspectionaircraft skin inspection

5 Network NDI Database Server Statistical Analysis Server Aircraft Configuration & Condition Server Remote Workstation Control Coin-tap Test Visual Inspection Navigation Robot-aided Aircraft skin inspection

6 Physics in Coin-tapping bell-like resonance vs. typical coin- tapping:bell-like resonance vs. typical coin- tapping: –global vs. local excitation –number of relatively high-Q modes difficulties in coin-tapping analysis: difficulties in coin-tapping analysis: – how “local” is suitable?

7 Prior work in impact & coin-tap test rigid body mechanics too simple to helprigid body mechanics too simple to help W. Goldsmith laid out the basic analysis using elastic media mechanics (1960)W. Goldsmith laid out the basic analysis using elastic media mechanics (1960) P. Cawley numerically simulated the process in very simplified settings (1988)P. Cawley numerically simulated the process in very simplified settings (1988) simplified 1st-order model (single-spring model) most widely usedsimplified 1st-order model (single-spring model) most widely used

8 Simplified 1st-order model (single-spring model) time Displacement

9 Single-spring model (continued) time impact force

10 Single-Spring Model in Practice (acceleration waves) A typical acceleration wave form (normal airplane skin, with supported understructure configuration) Time (ms) Acceleration amplitude (not calibrated)

11 Sound data waveform pro: less sensitive to tap vector con: more sensitive to environment noisepro: less sensitive to tap vector con: more sensitive to environment noise Sound amplitude Time (ms)

12 Acceleration-sound amplitude acceleration waveform is sensitive to tap variationsacceleration waveform is sensitive to tap variations sound has a clean free-vibration partsound has a clean free-vibration part Sound amplitude Force amplitude Time(ms) Time(ms)

13 Acceleration-sound power spectra Free-vibration sound — stronger patternsFree-vibration sound — stronger patterns Sound (free vibration) spectra db 5 kHz 10 kHz 15 kHz 20 kHz frequency 8 kHz 2.67 kHz Sound (whole process) spectra db 5 kHz 10 kHz 15 kHz 20 kHz frequency 8 kHz 2.67 kHz Force spectra db 5 kHz 10 kHz 15 kHz 20 kHz frequency 8 kHz 2.67 kHz

14 What can we discriminate? Normal skin, supported Normal skin, unsupported Patched skin, supported Patched skin, unsupported

15 Results (1/3 power ratio)

16 Conclusion force-time waveform is a good indicator of whether an impact is good or notforce-time waveform is a good indicator of whether an impact is good or not it also tells when free-vibration beginsit also tells when free-vibration begins free-vibration sound is the best indicator of substrate conditions — especially shallow delamination conditionsfree-vibration sound is the best indicator of substrate conditions — especially shallow delamination conditions

17 Further research Scan regions by coin-tappingScan regions by coin-tapping Apply spatial pattern recognitionApply spatial pattern recognition Characterize structural condition via transfer functionCharacterize structural condition via transfer function

18 Robot with sensors microphone accelerometer

19 force sound free-vibration normal, supportedpatched, supported normal, unsupportedpatched, unsupported


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