Global calibration of visual inspection system based on universal robots

Abstract

An on-line and flexible visual inspection system based on universal robots was introduced for the car body-in-white (BIW) and two practical global calibration methods by using a laser tracker and a measuring arm were described in complexity field environments. The method based on a measuring posture realized the coordinate transformation between the sensor coordinates and the system reference coordinate by combining the sensor coordinates with the target coordinates through the mechanical constraint. And the method based on the robot kinematics realized the global calibration at arbitrary postures by establishing a robot coordinate frame in fields and by obtaining hand-eye calibration relation through the coordiate transformation. Experimental results show that the standard deviations of repeatability for the measurement equipment and the system are 0.07 mm and 0.13 mm respectively, which indicates that both the methods can meet the requirement of monitoring the manufacture dimension changes of BIW. Futhermore, the coordinate measuring errors of the system are ±0.2 mm and ±0.8 mm from the two methods, respectively.