Research On6R Articulated Robot Calibration Methods And Experiments

As the improvement of productivity and rapid development of technology, there is an increasingly demand of high performance of6R articulated industrial robot based automated flexible production line from the manufacturing industry. Therefore, developing and establishing the analytical and experimental methods for robot calibration with self-intellectual property becomes the basic requirement to the manufacturing equipments.This paper took6R articulated industrial robots as researching objects. Based on the targets of improving static pose performance, we conducted the studies on robot calibration methods and experiments. Starting from the evaluation and measuring methods of pose performance, we firstly analyzed the sources of the pose errors for the robot end-effector. In order to model and simulate the influence to the pose errors from geometric parameters and non-geometric parameters, we established the robot kinematic error model and stiffness model, respectively. Meanwhile, based on parameters optimization solving methods, we built relevant experimental platform to identify the key parameters and compensate the pose errors of end-effector. Finally, according to the needs of enterprise, we established experimental platform for the industrial robot performance testing to provide an effective approach of measuring and evaluating the performance of self-developed6R articulated robots. The main contents of this paper included:According to the methods and principles of robot calibration, firstly, we derived and analyzed the static pose performance of6R articulated robot. Considering the testing criteria of pose performance in ISO9283, we used laser tracking system to establish the related experiment platform which worked as a supplement for the testing approach. For more, we designed a pose performance testing end-effector, whose flexible measuring accuracy was simulated and evaluated in terms of Monte-Carlo method.Taking into account of the characteristics of6R robot kinematics, we established the kinematic error model by MD-H and POE methods, respectively. Took15kg spray painting robot as the measuring object, we used the laser tracking system to build the experiment platform for the calibration of geometric parameters. In terms of using the Least-Squares optimization method, we identified and compensated the errors of geometric parameters. Further, we analyzed and evaluated the results for pose accuracy before and after the compensation.Considering the compliant feature of6R articulated robot, we analyzed the robot stiffness model and proposed a6-dimensional joints deformation assumption based robot stiffness model which was built on the kinematics of rigid body and rotational joint deformation assumption based stiffness model. Took KUKA KR16L as the researching object, we established the experiment platform to identify the joints stiffness. Further, we applied the Monte-Carlo method to simulate the errors of geometric parameters and to verify the estimation results. Meanwhile, we took the15kg spray painting robot in maintenance state as the researching object and built the experiment platform to identify the6-dimensional joint stiffness matrices. By means of using the iterated weighted Least-Squares optimization techniques, we obtained results. To verify the6-dimensional joints stiffness, we tested the pose accuracy and vibration characteristic of the end-effector before and after the compensation procedure.Considering the lightweight feature of self-developed15kg spray painting robot, we used the fixture theory to identify the links stiffness and evaluated its effect on end-effector pose accuracy. First, we derived the relationship between stiffness of link-fixture system and stiffness of the link. Then, we applied the laser tracking system and loading system to establish the identification experiment platform. Further, by using the non-linear Least-Squares optimization method, we estimated the stiffness matrices of link4,5and6. To evaluate their effects on pose accuracy, we proposed the evaluation approach by means of robot kinematics theory, Monte-Carlo method and Enumeration method to analyze its distribution status within working envelop. Finally, according to the influence feature, we simulated the stiffness status and evaluated the rationality for a specified painting trajectory.According to the needs of testing and evaluating the performance of industrial robot from enterprise, we tested the important performance characteristics for3typical6R articulated robots in flexible production line, such as pose accuracy, pose repeatability and path velocity characteristics. The tests were based on the criteria within ISO9283and the experiment platform was built in terms of the laser tracking system. Finally, the testing results were evaluated and compared numerically.