Calibration of robotic area sensing system for dimensional measurement of automotive part surfaces

This paper presents new calibration methods for a robotic area sensing system developed for industrial manufacturing inspection. A pixel-to-pixel calibration scheme is introduced to obtain standoff and baseline distance of the developed area sensor. In the three-dimensional (3D) space, the area sensor also has an offset angle in a plane parallel to the reference plane. Calibration of this offset angle improves the measurement accuracy. This pixel-to-pixel scheme is particularly useful for calibrating a 3D optical area sensor with off-the-shelf lenses. An exploding vector method was also developed to transform the measured depth map to a 3D point cloud. A robotic area sensing system was developed by integrating an area sensor prototype and a robot sensor planning system. Calibration of the integrated system includes robot calibration, part calibration, and robot hand-eye calibration. Calibration error of the robot system is related to the area sensor positioning accuracy in the robotic system. Experimental results show a successful practice of the developed robotic area sensing system. Measurement performance of the developed system can be improved if advanced lenses are adopted.