The 9 Points Calibration Using SCARA Robot

Abstract

The vision system is always applied to industrial in many applications. There are many applications that integrated with industrial robots by using vision system such as detecting position, and matching objects. Therefore, it is necessary to transfer from camera position in pixel coordination to robot position in world coordination. After calibration, robot can know the objects position and orientation, which be detected from vision system. In basic camera calibration to robot coordination, it needs at least 3 points of camera and robot positions. However, the accuracy from the algorithm will be low from human error, internal hardware such as intrinsic, extrinsic camera parameters, and installation error (Ex: tilt etc.). Thus, origianally, the process of calibration must have 3 steps, intrinsic camera calibration, extrinsic camera calibration and camera to robot base calibration. Moreover, the basic calibration cannot calculate TCP offset (Tool coordinate point offset). If tool has been installed to robot, the robot must change final position from MIF (Mechanical interface) to TIF (Tool interface). Thus, user must calculate the TCP offset before calculate camera calibration. However, there are many processes of calibration. In this paper, it will show the 9 points calibration's algorithm, which be applied from other applications of vision system. The paper will explain step-by-step how to solve the equation and how to apply with SCARA robot. Moreover, the paper will explain not only camera calibration, but also SCARA robot and TCP offset calculation.