Experimental validation of a 3-D vision-based measurement system applied to robot calibration

one of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. a large number of robot measurement systems are now available commercially. yet, there is a dearth of systems that are portable, accurate and low cost. in this work a measurement system that can fill this gap in local calibration is presented. the measurement system consists of a single ccd camera mounted on the robot tool flange with a wide angle lens, and uses space resection models to measure the end-effector pose relative to a world coordinate system, considering radial distortions. scale factors and image center are obtained with innovative techniques, making use of a multiview approach. the target plate consists of a grid of white dots impressed on a black photographic paper, and mounted on the sides of a 90-degree angle plate. results show that the achieved average accuracy varies from 0.2mm to 0.4mm, at distances from the target from 600mm to 1000mm respectively, with different camera orientations.