Binocular Vision-based Three-dimensional Contouring Error Calibration Method for NC Machine Tools

doi:10.3901/JME.2019.10.001

Abstract

Abstract: Contouring error is a key indicator for evaluating the dynamic characteristic of NC machine tools. Accurate periodic assessment of contouring error of machine tools guarantees the improvement of the machine tool manufacturing precision. To overcome the limitations of measurement range, measurement dimensions and measurement trajectory forms of the existing measurement equipment, a binocular vision-based three-dimensional contouring error calibration system and method is proposed, realizing the three-dimensional error measurement of an arbitrary trajectory in conditions of wide motion range. First, a cooperative target with high uniform illumination and high-precision enhancement marker is designed and then installed on the workbench, in which the circle marker which can be imaged with high quality is utilized to characterize the movement position of NC machine tools. Then, an eccentricity compensation algorithm is implant to calculate the position of the marker in image coordinate frame, solving the circular affine distortion in image processing. Thereafter, a data transformation method based on global modeling of camera imaging is proposed, and the three-dimensional coordinate of the marker are constructed and converted into the machine tool coordinate frame. Finally, the contouring error can be calculated by comparing the measurement curve with nominal curve. Experiments for the detection of contouring error of three-leaved rose curve is performed in a self-established five-axis machine tool. The feasibility and accuracy of the proposed vision measurement method are verified by the cross grid-encoder. The results show that the maximum error of vision measurement method for a feed rate of 1 500 mm/min is 9.97 μm and the average measurement error is 3.36 μm.

Key words: binocular vision, contouring error, five-axis machine tool, image processing, machine tool errors

CLC Number:

LIU Wei, LI Xiao, LI Hui, PAN Yi, JIA Zhenyuan. Binocular Vision-based Three-dimensional Contouring Error Calibration Method for NC Machine Tools[J]. Journal of Mechanical Engineering, 2019, 55(10): 1-9.

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