Relationship Model Of Tested Surface Geometric Feature And Eddy Current Displacement Sensor Measuring Error And Error Compensation

Due to the ability of noncontact measurement, insensitivity of tested surface finish and appropriateness for on-site measurement, eddy current displacement sensor provides an effective method for displacement measurement of metal parts in engineering industry. Optimal measuring accuracy is obtained when measuring plane because that eddy current displacement measuring method is based on the mutual inductance of the plate conductor and the coil. However, the research object of eddy current displacement measurement is changing from plane to complex curved surface, which means there is still some key problems restricted the measurement accuracy involved when measuring non planar surface. Aiming at solve the key problems of eddy-current measurement in singular geometry area, the model of relationship between tested surface geometric feature and eddy current displacement sensor measuring error and error compensation are researched. The major research work is as follows:Due to the edge feature extraction problem in irregular surface measurement using eddy current senor, the influence mechanism of edge feature to output signal is qualitatively analyzed. An inverse method of edge feature is proposed considering lift-off height and scanning speed. Furthermore, an inverse algorithm of edge feature position is built based on the identification of mutational point in electric signal curve. The influence of lift-off height and scanning speed to edge position is researched in experiments, which is verified with experimental calibration results.In order to analyze the influence of tested surface geometric feature to coil impendence and eddy-current field distribution, the model of relationship between sensor electromagnetic properties and tested surface geometric features is built. The theoretical numerical calculation for eddy current sensor measuring surface parts is conducted via the finite element method, which analyzes and proves the variation trend of current density in parts and coil impedance under the influence of different tested surface shape and measuring distance.According to the overall scheme of surface measurement by eddy current displacement sensor, an experimental curved surface displacement measuring calibration system is established. Experiments reveal the impact of different testing surface profiles on the signal output of the sensor, and the errors generated. Then calibration experiments of cylindrical and spherical parts with different curvature are conducted. Also the relationship of the measuring height, the radius of curvature and the output signal is quantitatively analyzed, which provides the basis for building the error compensation model..By displacement detection experiments, the positioning stability, measurement accuracy, repeatability and linearity of the eddy current displacement sensor are analyzed. Then the error influential factors which affect the measurement accuracy in previous experiments are further discussed. The results indicate that the stability, linearity and repeatability of the eddy current sensor are reliable. The edge position inversion algorithm and curved surface measurement error calibration technology that proposed in this research provide theoretical basis and lay the foundation for parts scanning measurement and surface normal vector measurement.