Evaluation of coded excitations for autonomous airborne ultrasonic inspection

Zhang, Dayi and Watson, Robert and Dobie, Gordon and MacLeod, Charles and Lines, David and Galbraith, Walter and Mineo, Carmelo and Pierce, Gareth (2019) Evaluation of coded excitations for autonomous airborne ultrasonic inspection. In: 2019 IEEE International Ultrasonics Symposium, 2019-10-06 - 2019-10-09, SECC. (https://doi.org/10.1109/ULTSYM.2019.8926048)

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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.