Analysis and improvement of the positioning accuracy of rotary axes of compound machine tools based on pitch error compensation

Abstract

A method for pitch error compensation analysis and parameter identification for a rotary axis with special structures is proposed to improve the positioning accuracy of the rotary axes of compound machine tools. The characteristics of the planar linkage mechanism of a rotary axis are analyzed. Then, the error compensation trend is obtained according to the corresponding relationship between the angle and the displacement. An angular positioning error piecewise function is used to represent the ideal effect and actual performance of the pitch error compensation of the rotary axis. The rotation positioning accuracy test of the rotary axis is completed with a laser interferometer and rotary calibration device. By the measured angular positioning error of the non-compensated points, the Levenberg–Marquardt algorithm is used to identify the parameter of the piecewise function, and the optimized linkage parameters of the rotary axis are obtained. By the measured angular positioning error of the integer points of the rotary axis, the pitch error compensation value is modified. The distribution of the calculated and measured angular positioning error of the rotary axis under the pitch error compensation is consistent. The compensation results show that the positioning accuracy of the rotary axis can be greatly improved and that it meets the work requirement of the compound machine. The piecewise function of pitch error compensation, linkage parameter identification and improved method of pitch error compensation proposed in this article offer certain reference and application value. The results can improve the rotation positioning accuracy of the rotary axes of machine tools with planar linkages.