Pose Calibration And Trajectory Adjustment Of Spray Painting Robot Based On Virtual Camera

During spray painting process of robot, the pose error of the workpiece will lead to a decline in the coating quality and negative effects on the appearance of products. Usually dedicated fixtures are employed to eliminate the pose error. Another solution is to measure of the pose error by contact measurement method and then adjust the spray painting trajectory. But in the business of quickly automobile repairing, the dedicated fixtures are costly and the measurement method is inefficient. To deal with such workpiece pose calibration issue and spray painting trajectory adjustment problem during robot operations, this thesis propose a scheme of workpiece pose calibration and spray trajectory adjustment based on virtual camera. The thesis primarily studies on several aspect:Regarding to the error between actual pose and ideal pose, this thesis analyzes the influence on the spray painting result, caused by pose error of the workpiece, and proposes a system of the workpiece pose calibration and spray painting trajectory adjustment based on virtual camera. Meanwhile the systematic design is accomplished and the principle and workflow of the scheme is described.The camera model is derived from the relationship between the inner coordinate system of the camera and the world coordinate system. The SURF algorithm is applied to extract the feature points of the target image and the reference image, and the matching result is optimized by using RANSAC algorithm.Based on the essential matrix between the target image and the reference image, this thesis proposes a method to calculate the relative pose between the virtual camera and the real camera. A criterion is proposed afterwards to exclude the undesirable redundant solutions after analyzing the multi-solution condition. The formula of trajectory adjustment is derived based on the result of the pose calibration.The design of the hardware and software of the spray painting robot is accomplished and the automatic spray painting operation of robot is realized on the workpiece. The experiments under different pose error conditions of the workpiece verify the effectiveness of the calibration method: the translational calibration error is within 3cm, and rotational calibration error is within 1°. The results of the trajectory adjustment simulations and experiments reveal that this spray painting robot with novel pose calibration and trajectory adjustment system is capable of practical spray painting applications.