基于视觉测量的XY-Theta并联平台分步运动学标定

Step Kinematic Calibration of a XY-Theta Parallel Stage Using Vision-based Metrology

针对一种用于丝网印刷的平面3自由度(Three-degree-of-freedom,3-DOF)并联平台,提出一种基于视觉测量的分步递进的运动学标定方法,解决这类特殊平面并联平台的运动学标定问题。结合矢量法和解析法,建立终端位置和姿态误差与几何误差之间的映射关系,得到误差雅可比矩阵。兼顾测量成本和实用性,搭建双相机全位姿视觉测量系统,通过高精度光刻玻璃进行标定。基于精密视觉测量,对并联平台的重复定位精度进行评估,在此基础上,设计一种分步递进的误差测量、参数辨识、误差补偿试验方案。标定后,终端最大位置误差从标定前的316μm下降至9μm,最大姿态误差从标定前的3.5×10–3°降至1.7×10–3°,该试验结果表明并联平台的终端定位精度得到了显著改善,验证了分步递进的运动标定方法的有效性。

A step and gradual kinematic calibration method using vision-based metrology is proposed for a three-degree-of-freedom （3-DOF） planar parallel stage for screen printing, and it solves the kinematic calibration problem of this class of special planar parallel alignment stages. The mapping relationship between the errors of position and orientation and the errors of geometrical parameters is derived by a combination of vector method and analytical method. The Jacobian matrix is obtained. The vision-based and full-pose measuring device including two cameras is set up by taking into account both measurement costs and applicability, and the device is calibrated by a high accuracy lithography glass-board. By using precision vision-based metrology, based on the repeatability of the parallel alignment stage, a step and gradual kinematic calibration including step measurement, step identification and step compensation is designed. After calibration, the maximum position and orientation errors are reduced from 316 μm and 3.5×10-3° to 9 μm and 1.7×10-3°, respectively. The results show that the positioning accuracy after calibration is significantly improved and verify the effectiveness of the step and gradual kinematic calibration method.