Design and Optimization of an Eddy Current Speed Sensor for Rotating Rods

This paper presents the design and optimization of a novel eddy current speed sensor for rotating rods and cylindrical shafts. The sensor consists of one excitation coil and two pick-up coils. All coils are stationary; we consider air coils, and we also use a magnetic yoke. We utilize a copper coating on an iron rod to increase the sensitivity, and we compare the performance with the performance achieved for an uncoated iron rod. 3D FEM is utilized for analyzing and for optimizing the design of the proposed sensor. The main advantages of the novel sensors are their simplicity, their low cost and their robust configuration. A linearity error of 0.5% has been achieved. The level of accuracy is limited by mechanical factors. A 1D analytical model has also been developed for rapid analysis and optimization of the sensor. An aluminum rod was also used in the measurements for a comparison with the results achieved with the iron rod.

I. Introduction

The electrification of transportation, e.g., electric cars, railways and airplanes, and also renewable energies are continuously increasing, and this especially involves replacing rotating mechanical elements with their electrical counterparts. Traction motors, electrically-assisted turbo chargers and other rotating elements need speed sensing for control purposes, and for diagnosing and preventing mechanical and electrical faults [1]–[8]. The simplicity of the sensor is of no less importance than its precision. Speed and position sensors often need compensation of mechanical issues, e.g., lift off and eccentricity. It is therefore a key advantage to use a sensor with a simple design for speed measurements.