On the Measuring System for the Position of Industrial Robots' End-Effectors based on Monocular Vision

The requirement of intelligent manufacturing technology for the accuracy of industrial robots becomes higher and higher. To improve the accuracy of industrial robots, kinematic calibration as a valid method is generally used, which requires the data of the end-effector's position. Unlike the existing method mainly depending on precision instruments such as laser trackers, a measurement system for the position of industrial robot's end-effector based on monocular vision is proposed, which includes an industrial camera, a standard sphere. Firstly, the Modified Denavit-Hartenberg (MDH) method is used to build the kinematic model of the industrial robot, and the industrial camera is installed on the end-effector of the industrial robot, which is used to measure the position of the standard sphere placed near the base of the industrial robot. Then the data of the ray from the optical center of the camera to the standard sphere's center are acquired by moving the industrial robot with different poses. The center of the standard sphere can be calculated by triangulation method. With the error model of the robot established, an objective function based on the kinematic model and the distance from the ray to the standard sphere center is obtained, and optimization methods are used to identify the kinematic parameters of the industrial robot.