Numerical and Experimental Investigations of Motion-induced Eddy Current for Contactless Speed Estimation based on Distributed Current Source Model

This paper presents a distributed current source (DCS) model for calculating the motion-induced eddy-current (EC) in a conductor with uniform rectilinear motion and its generated magnetic flux density. By discretizing the conductor into elemental current sources, EC is formulated in state space as an optimization problem for investigating the effects of motion-induced EC on measurements in manufacturing. Along with a parametric study on the effects of motion velocity on the choice of sensing points, the results are numerically verified by comparing with finite element analysis which show excellent agreements. Mechanical scanning has some influence on detection results but can be alleviated by carefully selecting the sensing points. This study has led to the assembling of a prototype sensor for contactless speed estimation. Two sets of experiments were conducted on a CNC to evaluate the accuracy and response speed of the sensor which demonstrates high accuracy when measuring a stationary movement and fast response when dealing with a transient movement.