Estimation of the Pose of a Triple-coil Sensor Above a Planar Conductor

In eddy current (EC) testing, measurement signals are sensitive to the tilt angle and liftoff between the sensor and the conductor, with tilt angle being a major source of noise. This article introduces a small-sized triple-coil sensor designed for estimating sensor pose. The proposed method is prospective to be applied to the control of sensor pose, enabling compensation for data obtained at different tilt angles. To expedite computations, a simplified analytical model for the inductance of the tilted coil is derived using the integral median theorem and validated against the original analytical model, finite-element analysis, and experimental measurements. An inversion method for pose estimation based on the Newton-Raphson method is implemented. The results show the effectiveness of the proposed method in both numerical simulations and experiments.