The necessity to inspect essential infrastructure such as oil and gas pipelines for wear, and deterioration highlights the critical role of enhancing Non-Destructive Testing (NDT) methods. Routine inspection for wall thinning is essential for monitoring the structural integrity of these assets and preventing serious accidents. Given the challenges of manned access to these assets, Unmanned Aerial Vehicles (UAVs) equipped with high-resolution cameras are increasingly being adopted as a safer and more efficient alternative for remote inspections. However, their inability to detect sub-surface defects or assess thickness under coatings restricts their applicability. Pulsed Eddy Current (PEC) technology provides a promising solution, capable of assessing thickness beneath coatings and addressing the shortcomings of camera-based inspections. Traditional PEC systems are effective but bulky and difficult to incorporate within mobile platforms, limiting their versatility and ease of deplorability. This paper presents a novel, compact PEC sensor system to address these challenges, enhancing PEC inspections for mobile platforms. The system can be effectively mounted on a crawler-hybrid UAV, facilitating detailed 360-degree inspections of pipe surfaces. Findings detail the autonomous deployment of this PEC system via a UAV for the non-intrusive assessment of wall thickness. Finite element analysis was used for the design and performance evaluation of the PEC system. Integrated with a multirotor-crawler UAV engineered for navigating through complex pipeline environments, this mobile PEC system can conduct thorough evaluations of steel pipeline wall thinning. The system delivers a sensing method that achieves accurate thickness measurements, with errors under 4.8%, facilitating reliable and comprehensive asset inspections.

Guided wave Electro Magnetic Acoustic Transducers (EMATs) offer an elegant method for structural inspection and localisation relative to geometric features, such as welds. This paper presents a Lorentz force EMAT construction framework, where a numerical model has been developed for optimising Printed Circuit Board (PCB) coil parameters as well as a methodology for optimising magnet array parameters to a user’s needs. This framework was validated experimentally to show its effectiveness through comparison to an industry built EMAT. The framework was then used to design and manufacture a Side-Shifted Unidirectional Periodic Permanent Magnet (PPM) EMAT for use on a mobile robotic system, which uses guided waves for ranging to build internal maps of a given subject, identifying welded sections, defects and other structural elements. The unidirectional transducer setup was shown to operate in simulation and was then manufactured to compare to the bidirectional transmitter and two-receiver configurations on a localisation system. The unidirectional setup was shown to have clear benefits over the bidirectional setup for mapping an unknown environment using guided waves as there were no dead spots of mapping where signal direction could not be interpreted. Additionally, overall package size was significantly reduced, which in turn allows more measurements to be taken within confined spaces and increases robotic crawler mobility.

Guided wave ranging measurements offers an elegant method to localize an inspection robot relative to the geometric features, such as welds, of a structure under test. This paper characterizes the suitability of various EMAT generated guided wave modes when reflecting from butt welds for the purpose of choosing a low frequency mode suitable for accurate ranging. Wave modes were tested in 10mm mild steel plate in experiment and simulation, the method of data extraction is discussed as well as the determination of the wave mode best suited for weld ranging by means of comparison of the reflection coefficients. The authors conclude SH1 at a frequency-thickness product of 2 MHz.mm, is shown to be a highly suitable wave mode for gaining a large reflection from a weld, with an average reflection co-efficient of approximately 0.45 across four different sized weld crowns. A ranging over 1 meter experimentally was demonstrated to have a 2.65% error using our method. This work will enable simultaneous detailed mapping through ranging and inspection of large welded structures by mobile robotic inspection systems using EMAT’s.