Multiparameter Eddy-Current Sensor Design for Conductivity Estimation and Simultaneous Distance and Thickness Measurements

Smart sensing is a prerequisite to information sharing in intelligent manufacturing where online measurements of multiple parameters are essential to infer system properties for process analysis and product-quality control. This paper presents methods to develop a novel eddy-current (EC) sensor capable of simultaneously measuring multiple parameters of a nonferrous electrically conductive workpiece (WP). Unlike traditional EC-sensors that base principles on lumped-parameter impedance or voltage change, the proposed method (referred to here as a multiparameter EC-sensor) directly measures the EC-generated magnetic flux density (MFD) to determine the displacement, thickness, and electrical conductivity of the WP. Specifically, an analytical model that characterizes the impedance and MFD field generated by the induced EC is presented, from which the design criteria for developing a multiparameter EC-sensor are established. The proposed methods, along with a prototype MFD-based EC sensor, have been validated and evaluated experimentally for simultaneous distance and thickness measurements and conductivity estimation of a titanium thin-walledWP in a lathe-turning process.