Stiffness Modeling Of Robotic Drilling System And Stiffness Performance Optimization Based On Robot Machining Pose Adjustment

Automate intelligent equipment using 6R serial robots as flexible carriers are playing an increasingly important role in the manufacturing industry.At present,most of the research objects of stiffness model are parallel mechanisms,and the contents of stiffness model rarely considered the stiffness of hole-making end-effectors.Based on the summary of the current research status in locally and abroad,the main contents of this article are as follows.(1)This thesis has built a robotic drilling system for hole-making tasks,including an industrial robot,a drilling end-effector,and a hole-making auxiliary workbench.Based on the Quaternion Algebra,parametric modeling of the general 6R tandem robot was carried out.The general method and steps of robot kinematics solution based on quaternion were studied.On this basis,the robot drilling workstation was laid out and the integrated design of the workstation was completed.(2)Based on VJM(the virtual joint method),the joint stiffness model of the hole-making robot was established.From the identified joint stiffness values,the maximum positional deviation of the drilling robot's theoretical and actual deformation values in the X direction of the coordinate axis under external force is27.73%,The maximum azimuth deviation is 6.74°,which can predict the deformation of the hole-making robot in the X-axis direction by more than 72%;the maximum position deviation in the Y-axis direction is 22.81%,and the maximum azimuth deviation is 10.69°,which can predict the deformation in the Y-axis direction is more than 77%;the maximum position deviation in the Z direction of the coordinate axis is 35.41%,and the maximum azimuth deviation is 10.99°,so the stiffness model can predict the deformation of the drilling robot in the Z-axis direction by more than 64%.In addition,based on the assumption of Euler-Bernoulli beam,the stiffness model of the end-effector was established;based on the principle of linear superposition,the overall stiffness model of the robotic drilling system was established,which improves the integrity of the rigidity model of the robotic hole-making system.(3)To evaluate the Cartesian stiffness performance at the end of the drilling system,the concept of Stiffness Ellipsoid was introduced.And the axial direction stiffness and cutting plane stiffness of the system were defined aims to evaluate the stiffness performance of the system during machining.Using the control variable method,the effect of robot machining posture and tool specifications to the end stiffness performance of the drilling system was explored.Besides,a method for optimizing the system's stiffness performance of the whole system combining the robot's machining posture,machining safety,and robot's kinematics performance was designed.Finally,a software system for the robotic drilling host computer was developed based on the PC interface.The drilling experiment showed that the maximum error of these hole diameter within 0.05 mm after stiffness optimization,which can satisfy the common hole-making requirements of aluminum materials in the aviation and automotive industries,and the effectiveness of system stiffness performance optimization for robot drilling was verified.