A Surface Normal On-Machine Measuring Method Using Eddy-Current (EC) Sensor Array

Abstract

Normal vector measurements of the machining point and attitude adjustments of the end effector are key aspects to meet the technological requirements of hole verticality in auto-drilling and the residual wall thickness in mirror milling. In this paper, a surface normal on-machine measuring method using an EC sensor array is proposed. The influences of the object surface inclination and the sensor array arrangement on the performance of EC displacement sensors were investigated, and the sensor measuring errors from coupling interference were effectively eliminated. Moreover, a practical calibration algorithm was established in which the positions of the EC sensors in a normal vector calculation model were accurately corrected. The feasibility of the measuring method was validated through a calibration experiment, as well as a measurement experiment based on the calibration results. The accuracy of a normal vector measurement is improved when applying the accuracy compensation and position calibration algorithm of an EC array to engineering practices.