A tracking approach of a moving ferromagnetic object using triaxial search coil data

In this article, we propose a novel method for tracking a moving ferromagnetic object in terms of search coil data. The magnitude of the search coil data is proportional to the velocity of the moving target. By analyzing the characteristics of the search coil data, we found the movement of the ferromagnetic object converts the static magnetic field into signals with non-zero frequencies. The search coil data can provide a higher sensitivity to the model parameters than the magnetic gradient tensor data in detecting a moving magnetic object. Localization and estimation of the velocity and magnetic moment are implemented in steps due to the coupling among the object parameters. We use a least square method to estimate the trajectory of the moving object. The magnetic moment and velocity are estimated on the inferred object coordinates. A fourth-order polynomial is applied to fit the velocity curve to suppress errors from the inferred coordinates. We design three synthetic examples, with and without random noise, to validate the proposed method. The locations, velocities and magnetic moments of the moving ferromagnetic target can be well determined. The proposed method has also been applied to a field test, the strong overlap between the acquired target signal and the estimated target signal indicates that the proposed method can estimate the target moving trajectory, velocity and magnetic moment accurately.