Sensitivity and Lift-Off Robustness of Magnetic Resonance Circuit Topologies for Enhanced WPT-Based ECT Systems

Electromagnetic sensors’ response is affected by lift-off variations, which are caused by nonmagnetic coating thickness, surface roughness or sensor vibrations. These variations affect eddy current testing (ECT) sensitivity, defect quantification and reconstruction of material properties. This paper compares different magnetic resonance circuit (MRC) topologies as signal conditioning for improving ECT system response to various lift-offs. The MRC is designed to operate at maximum energy, with the potential of several resonances, which lead to enhanced response for optimal and multiple feature extraction, improving signal-to-noise ratio (SNR) and increasing sensitivity to cracks. The proposed paper designs and investigates the effect of different MRC topologies connected to ECT systems to inspect a steel block with surface cracks. The performance comparison of the proposed systems provides the advantages and limitations of different MRC approaches for multiple resonance potentials, higher SNR and response sensitivity at different lift-off distances. The advanced MRC, featuring series and shunt topologies in each transmit and receive coil, is the most immune to noise, with an SNR of 49.9 dB at a 3.4 mm lift-off using its first peak frequency feature. Its response is less crack-sensitive, with a sensitivity of up to 1.5% at 0.6 mm lift-off.