Calibration of 6-DOF Industrial Robots Based on Line Structured Light

Abstract To improve the accuracy of an industrial 6-DOF robot, this paper proposes a new calibration method based on a line structured light measurement system. The line structured light measurement system mounted on the end-effector is used as a tool to acquire the three-dimensional coordinate information of the centre of a standard sphere. Hand-eye calibration is used to establish the transformation between the robot and the measurement system. A combined kinematic model that includes both the kinematic parameters of the robot and the initial hand-eye relationship is established by applying the modified Denavit and Hartenberg (MDH) model. An error model is derived based on the principle that the coordinate of the sphere centre is invariant in the base frame of the robot. Consequently, the errors in the kinematic parameters of the robot and the hand-eye relationship can be identified by substituting the measurement results and the original parameters of the robot into the error model. The results of the simulations and experiments show that the accuracy of the robot is significantly improved by implementing the proposed calibration method. The proposed method is effective, simple, time-saving and low-cost and is therefore a suitable candidate for on-site calibration of industrial robots.