| Nowadays, the repeatability accuracy of the robot produced by robot manufacturers is very high, while its absolute accuracy is very low. As the robot off-line programming is applied widely, it's a key technique to improve the robot absolute accuracy. A kinematics calibration method is designed, that it adopts advanced laser tracking measurement system and model-based parameter identification to identify the accurate parameters of a 6R welding robot and increase the absolute accuracy.At first, aiming at the industrial robot calibration and combining the robot's real geometrical structure, the link coordinates system of the robot is established by D-H method. On this basis, detailed kinematics and kinematics inverse solutions are calculated, and the Jacobian matrix is also solved. Then, simulation test for the kinematics equation is taken with Matlab language. Through comparing the test result and the location data in the robot controller, the validity of the established kinematics model has been proved.Aiming at the robot's geometrical structure, the error sources influencing the robot's absolute accuracy are analyzed. Adopting an optimized kinematics model and the differential transform method, the error model for the robot calibration is solved, and the calculation programs are designed based on Matlab language and least squares algorithm. Through designing a simulation test for the error model, the reliability of the model has been proved.Finally, three calibration schemes are designed on the basis of error model, including the measure based on the standard hole, standard plane and laser tracking. Their advantage and shortage are compared and analysed from the method theory, data collection and calibration result, respectively. After compensating the kinematics parameters error into the robot controller, through measuring and analyzing the robot end-location, the calibration method improving the robot absolute accuracy has been proved. |
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