解决约束平面偏移问题的机械臂闭环标定

基于平面约束的工业机械臂闭环标定，拟合平面与实际约束平面之间存在一定偏差，直接影响标定精度.针对此问题提出消除偏差的方法及误差模型.建立平面坐标系，得到约束平面的准确方程，通过接触式测量头对约束平面进行测量，在平面坐标系中描述测量点的位置；建立最小完整连续运动学模型，从而减少冗余参数的影响；利用双目视觉定位约束平面并规划理论测量点位置，实现自动化测量；通过改进的最小二乘法对参数误差进行辨识.实验结果表明，修正运动学参数后，机械臂绝对位置精度由1.234 mm提高到0.405 mm.该方法成本低、精度高、效率高，且简化了误差模型，适用于工业机械臂的现场标定，为机械臂生产厂家实现批量化标定及后期设备维护提供了思路.

Closed loop calibration of industrial robot for solving constraint plane wandering

The fitting plane wanders from real constraint plane when an industrial robot is calibrated based on planar constraint, which influences the accuracy of closed loop calibration directly. A method was proposed as well as the corresponding error model. The planar coordinate system (PCS) was built to achieve the exact equation of constraint plane. A trigger probe was used to measure the constraint plane, and the position of each measurement point was described in PCS. A complete, minimal and continuous kinematic model was established to reduce the influence of redundant parameters. The stereo vision system was applied to locate the constraint plane and plan the theoretic position of measurement points to realize automatic measurement. The identification of all kinematic parameters were accomplished by the modified least squares. Results showed that based on the proposed calibration method and error model, the absolute positioning accuracy of the industrial robot was enhanced from 1.234 mm to 0.405 mm after the modification of kinematic parameters. The proposed method has the advantages of low cost, high accuracy and high efficiency, and can simplify the error model. It is applicable for the on-site calibration of industrial robot and provides a reference for robot manufacturer to achieve batch calibration and subsequent equipment maintenance.