Dry-coupled ultrasonic thickness measurement deployed using an over-actuated unmanned aerial vehicle
R J Watson, M Kamel, D Zhang, C N MacLeod, G Dobie, S G Pierce and J I Nieto
Modern industrial inspection activities are witnessing an increasing adoption of robotically enabled remote evaluation solutions, especially in scenarios where the task requires a human operator to enter an inaccessible or otherwise dangerous locale. This can include a number of strategies, such as inclined surface crawlers or climbers and underwater rovers, but of particular interest in recent years are multi-rotor unmanned aerial vehicles (UAVs). Conventional under-actuated UAVs are now routinely used for visual surface inspections of a range of structures (including wind turbines, bridges and petrochemical storage tanks), but lack the ability to physically interact with their environment due to an inability to produce horizontal thrust when hovering horizontally. Employing over-actuated control (for example by introducing tilt capability into the rotors), enables the generation of arbitrarily oriented thrust and therefore allows the possibility of contact measurements of a structure while hovering next to it. This work details the successful deployment of a dry coupled ultrasonic probe from an over-actuated UAV. Thickness measurements were performed on a sample of aluminium plate using a 5 MHz dual-element piezoelectric transducer, proving the concept of UAV deployed ultrasonic measurements not requiring liquid or gel couplant or relying upon magnetic adhesion.
