Improved Design of an Eddy-Current Speed Sensor Based on Harmonic Modeling Technique

This study proposes an improved design of an eddy-current speed sensor (ECSS) by adding a ferromagnetic core to the stator, resulting in a sensitivity enhancement ranging from three to sixty times compared to a reference model according to shaft materials. An improved analytical model (AM) based on harmonic modeling (HM) is developed to account for the effects of core permeability, validated through finite element analysis (FEA), demonstrating excellent agreement between the two methods. Based on this model, the optimal dimensions of the proposed design are obtained, and comprehensive analyses of shaft materials and excitation source parameters are performed. The results show that the magnetic shaft offers the highest sensitivity, while a nonmagnetic shaft with low conductivity ensures optimal linearity. Meanwhile, a nonmagnetic shaft with high conductivity leads to low sensitivity and higher linearity errors. Furthermore, a high-frequency excitation source enhances output linearity but necessitates careful selection based on the shaft materials. The dynamic characteristics of the proposed design under different operating conditions are analyzed using a coupled Ansys Twin Builder and Maxwell 2D model. The proposed design and AM significantly improve ECSS performance and the analyzing tool, providing a robust and practical solution for precise speed measurement in various applications.