Design and Research of Mutual-inductive Self-Nulling Orthogonal Eddy Current Sensor
To solve the problem that the sensor is prone to lift-off and shaking during eddy current testing(ECT)process,which causes defect misjudgment and leakage detection,the electromagnetic field theory was used to study the zero mutual inductance characteristic between the double pancake coils,thus designing a mutual-inductive self-nulling orthogonal eddy current(EC)sensor.Then an ECT system guided by an industrial six-axis robot was developed,and a series of experiments were carried out.Results show that the proposed EC sensor has better suppression of lift-off and shaking than the coaxial EC sensor when detecting defects in the cylinder structure,and surface cracks along the axial and circumferential directions of the cylinder can be clearly identified by rotating its excitation coil in the plane to 0° and 90°.The designed self-nulling EC sensor effectively solves the problem of misjudgment and leakage detection of defects caused by lift-off and shaking without relying on high-precision attitude calibration,which has important application significance for in-situ detection of the conductive structures in the external field.
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