Dry coupled ultrasonic non-destructive evaluation using an over-actuated unmanned aerial vehicle

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Unmanned Aerial Vehicles (UAVs) are seeing increasing adoption to automated remote and in situ inspection of industrial assets, removing the need for hazardous manned access. Aerial manipulator architectures supporting pose-decoupled exertion of force and torque would further enable UAV deployment of contact-based transducers for sub-surface structural health assessment. Herein, for the first time, we introduce an over-actuated multirotor deploying a dry-coupled ultrasonic wheel probe as a novel means of wall thickness mapping. Using bi-axial tilting propellers in a unique tricopter layout, this system performs direct thrust vectoring for efficient omnidirectional flight and application of interaction forces. In laboratory testing we demonstrate stable and repeatable probe deployment in a variety of representative asset inspection operations. We obtain a mean absolute error in measured thickness of under 0.10 mm when measuring an aluminum sample with varying wall thickness. This is maintained over repeated exit and re-entry of surface contact, and when the sample is mounted vertically or on the underside of a 45° overhang. Furthermore, when rolling the probe dynamically across the sample surface in an area scanning modality, a mean absolute error in wall thickness below 0.28 mm is recorded. Multi-modal operational confidence bounds of the system are thereby quantitatively defined.
Original languageEnglish
Number of pages16
JournalIEEE Transactions on Automation Science and Engineering
Early online date26 Jul 2021
Publication statusE-pub ahead of print - 26 Jul 2021


  • inspection
  • ultrasound inspection
  • unmanned aerial vehicle (UAV)-based remote sensing
  • dry-coupled ultrasound inspection
  • remote inspection
  • non-destructive evaluation (NDE)
  • over-actuation

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