Evaluation of Coded Excitations for Autonomous Airborne Ultrasonic Inspection

Abstract

Unmanned Aerial Vehicles (UAVs) are receiving increasing attention for use in Non-Destructive Testing due to their ability to access areas where manual inspection is not practical. Contact-based UAV ultrasonic inspections grant the opportunity to remotely monitor the structural health of an industrial asset with enhanced internal integrity information. Ultrasonic inspection is a Non-Destructive Testing (NDT) method conventionally used in corrosion mapping. Surface contacting ultrasonic transducers provide enhanced structural integrity information. However, due to near-surface aerodynamic effects, angular sensitivity of the ultrasound probe and alignment error during autonomous inspections, ultrasonic thickness measurements with low Signal-to-Noise Ratio (SNR) are common. Coded excitation consists of a series of binary bits, whereby the polarity of the voltage is varied following a set excitation sequence to produce desirable signal properties. Here, coded excitation is utilised to increase SNR and thereby reduce measurement uncertainty originating from non-ideal transducer alignment with asset surfaces during inspections. This paper evaluates the performance of two binary code sequences (8-bit Golay, 13-bit Barker) for use in autonomous airborne inspections.

Review of Current Simple Ultrasound Hardware Considerations, Designs, and Processing Opportunities

“…This is especially relevant in light of the recent development of device prototypes capable of producing ultrasound images using only piezoelectric organic lightemitting diodes (H. Yu et al 2020) and non-contact laser ultrasound systems (X. Zhang et al 2019). Developments like these have the potential to dramatically change the ultrasound hardware paradigm.…”

“…Other synthetic aperture techniques have been widely discussed, for example inRomero-Laorden et al (2013),Jeon et al (2019), and Lim, H. H. Kim, andYoon (2021), and an earlier article byBurckhardt, Grandchamp, and Hoffmann (1974). Similarly, monostatic synthetic aperture scanners (MSASs) and monostatic fixed focus scanners (MFFSs) are two approaches worth consideration in terms of improving image quality (NickBottenus et al 2015;Ylitalo and Ermert 1994;Heuvel et al 2017; S. Nikolov, J. Jensen, and Tomov 2008).At the pulser stage, barker codes (Dayi Zhang, R Watson, Dobie, et al 2019;Xiaochun Wang et al 2021(Isla and Cegla 2017).…”

Dry-Coupled Airborne Ultrasonic Inspection Using Coded Excitation

“…Previous research demonstrated a contactbased ultrasonic inspection, using a conventional transducer with a small amount of liquid couplant and deployed by an autonomous, multi-rotor UAV. The inspection was conducted by a UAV in an indoor laboratory [4], [5].…”