基于几何特征的铆接件精确装配视觉伺服控制方法

Visual servo control method of riveted parts precise assembly based on geometric features

针对目前铆接件机器人装配多采用示教再现方式实现,主要应用于固定工况的问题,为满足铆钉数量多、工况多变的铆接件装配需求,提出一种基于几何特征的铆接件精确装配视觉伺服控制方法。首先,通过将相机安装在机器人末端执行器平台,搭建基于机器人的铆接件自主对准的单目视觉系统,完成相机、机器人末端与基坐标系标定;其次,选取铆钉平面初始图像中的4个铆钉圆心作为特征点,以特征点之间的连线构造直线特征,利用直线特征与相机旋转运动间的交互矩阵设计基于线特征的铆接件姿态控制律,使得铆钉与铆钉孔轴线平行,从而保证装配过程中铆接件的相互平行;再次,选取铆钉平面初始图像中的4个铆钉圆心作为特征点,1个铆钉的轮廓作为圆面积特征,利用点特征与相机旋转运动的交互矩阵设计铆接件的姿态补偿项,进而利用点特征和圆面积特征与相机平移运动间的交互矩阵设计与姿态控制律相解耦的位置控制律,实现铆钉与相应铆钉孔轴线的重合。最后,采用六自由度机器人进行铆接件自主对准装配仿真。结果表明,以铆接件内部铆钉固有的图像特征作为控制输入,所设计的控制器能够实现铆接件的自主高精度对准。方法对于工业生产中多点对准装配的工况具有广泛的应用价值。

A visual servo control method was proposed for precise assembly of riveted parts based on geometric features,which can be applicable to the cases with many rivets and variable working conditions and is different from the existing teaching and reproducing methods.First,by installing the camera on the end effector platform of the robot,a monocular vision system based on the autonomous alignment of the riveted parts of the robot was built to complete the calibration of the camera,the robot end,and the base coordinate system.Second,four rivet centers in the initial image of the rivet plane were selected as the feature points,and then the line feature was constructed by the line between the feature points.A riveting part attitude control law was designed by using the interaction matrix between the line feature and the camera rotation motion,which made the rivet parallel to the axis of the rivet hole,thus ensuring that the riveting parts were parallel to each other during the assembly process;Third,by selecting four rivet centers in the initial image of rivet plane as feature points and the contour of one rivet as the circular area feature,the attitude compensation term of riveted parts was designed by using the interaction matrix between point feature and camera rotation motion.Then,the position control law was designed by using the interaction matrix between point feature,circular area feature,and camera translation motion,which was decoupled from the attitude control law and made the axis of rivet coincide with the axis of corresponding rivet hole.Finally,the six DOFs robot was used for the autonomous alignment assembly simulation of the riveted parts.The results show that the designed controller can achieve the autonomous high-precision alignment of the riveted parts by using the image features inherent in the rivets inside the riveted parts as inputs,and the method has wide application value for the multi-point alignment assembly conditions in industrial production.