基于单拉线编码器测量系统的几何标定及精度分析

Geometric Calibration and Accuracy Analysis Based on Single Draw-Wire Encoder

提出一种基于单拉线编码器测量系统的几何误差标定方法,通过在测量系统引入被测点位姿参数建立位姿求解模型,基于闭环矢量链建立测量系统误差辨识模型,采用最小二乘法对几何误差参数进行辨识。验证实例表明,标定后测量系统中几何参数最大绝对误差只有1×10-8μm,从而证明标定算法的有效性与高精度。进一步分析测量系统中动滑轮圆周度和转轴角度误差,拉线弹性变形,拉线编码器误差对测量系统精度的影响。分析结果表明,当拉线编码器的测量误差为0.0046mm,动滑轮的转轴误差为0.1°时,最优标定点数目为35个,测量系统的测量误差最大为0.037mm。

This paper proposes a geometric error calibration method based on single draw - wire encoder measurement system. By introducing the pose parameters of measured point to the measurement system, pose solution model was built. Then, error identification model was established based on closedloop vector chain. Besides, least square method was used to identify the error parameter. The testing example verifies the validity and high precision of the calibration method as the maximum absolute error of geometric parameter of the measurement system was only 1× 10^-8 μm after calibration. Further analysis was carried out to find influences on the precision of measurement system by different kinds of error, such as circular degree of pulley, rotation error, elastic deformation, error of draw- wire encoder. The analysis result indicates that when the error of draw wire encoder is 0. 004 6 mm, and the rotation error of the pulley is 0.1°, the optimum number of calibration pose is 35, and the maximum measuring error of the system is 0. 037 mm.