视觉引导抓取机械手工作平面定位误差与修正

Positioning and Correcting Errors of Operation Planes of Visually Guided Grasping Manipulator

采取视觉的方法对工作台上的产品定位,提出了1种空间已知平面上的点的定位误差模型。首先,建立单目视觉定位模型,得出工作台平面上的点的横纵坐标与该点的像面坐标之间的关系,实现该平面上的点定位。然后,根据径向畸变模型建立定位误差模型。最后,通过实验,对工作台平面上144个角点进行定位,用这144个角点的定位误差数据拟合该定位误差模型中的待定系数,并用最终确立的定位误差模型补偿144个角点定位误差。实验结果显示:该定位误差模型的两个待定常数的拟合确定系数高达0.9以上,经过定位误差模型补偿修正以后,工作台平面144个角点的两个坐标方向的最大定位误差由2.15 mm、1.94 mm显著降低到0.62 mm、0.29 mm。实验结果证明提出的单目视觉定位误差模型的正确性,并证明了影响成像系统畸变的主要因素是径向畸变。

In order to locate the workpiece,a positioning error model is established. First,based on the ideal pinhole imaging model,the relationship between the horizontal and vertical coordinates of the points on a plane in space and the image coordinates can be acquired to position the points on the plane. The analysis concludes that the key factor which affects the positioning error is the radial distortion of the imaging system. The positioning error model is established based on the radial distortion model. Finally,through experiments and camera calibration,144 corners of a planar checkerboard are located and undetermined coefficients of the positioning error model are fitted. The error analysis results indicate that the R-square of the fitting is up to over 0.9. After compensation by the positioning error model,the positioning errors of the 144 corners of the planar checkerboard are greatly reduced from 2.15 mm and1.94 mm to 0.62 mm and 0.29 mm. The analysis proves that the positioning error model based on monocular vision raised in this paper is correct and that the radial distortion is the key factor which affects the positioning error.