关键词: 工业机器人, 基准球, 奇异值分解, 视觉测量, 手眼关系, 现场校准

Abstract: Robot flexible coordinate measurement system can fulfill rapid online measurement of large workpieces. It is an important quality monitoring equipment on the automatic production line. Field calibration technology is one of the key technologies of the flexible coordinate measurement system. The calibration accuracy affects the measurement system precision directly. The hand-eye relationship between the robot flange coordinate and the vision sensor coordinate, the parameters calibration of the robot kinematics model and the establishment of the robot base coordinate system are the three main contents of the field calibration. The hand-eye relationship is established directly by using laser tracking and intermediate targets. Thus transformation accuracy is irrelevant to the robot’s kinematics error. The fast calibration of link parameters based on constant distance model is achieved by fixed calibration spheres. According to robot kinematics model and measuring results of laser tracker, transformation matrix is solved through registration based on singular value decomposition. Robot coordinate system is established precisely. After primary calibration by using the laser tracker, rapid online calibration can be realized with the reference sphere so that the influence of the model parameter variations on the measurement system can be decreased. The experiments show that the error of the whole measurement system is smaller than 0.2 mm after calibration.

Key words: Field calibration, Hand-eye relationship, Singular value decomposition, Vision measurement, Industrial robot, Reference sphere