Research On Stiffness Characteristic Analysis And Optimization Of 6-Dof Industrial Robot

Not only can industrial robots perform precision machining work in harsh working environments,they can also achieve a wide range of machining operations relative to traditional machine tools.As a result,industrial robots are being used in a wide range of manufacturing applications,including automotive and components,aerospace,rail transportation,and machining and manufacturing.However,multidegree-of-freedom tandem industrial robots have the disadvantage of low structural stiffness compared to machine tool machining,resulting in large deformation at the end of the robot when drilling,low drilling accuracy and poor quality.This paper focuses on the relationship between the six degrees of freedom tandem industrial robot posture and robot stiffness,using the FANUC R-2000 i C/165 F robot as the object of in-depth research,as follows.Firstly,according to the basic parameters of FANUC R-2000 i C/165 F robot,the kinematics model of the robot is constructed by using the modified D-H modeling method,and the solution method of forward and inverse kinematics equations is derived.The correctness of the kinematics model and kinematics equations is verified by MATLAB simulation;Jacobian matrix is constructed according to kinematics theory,and verified by vector product method and MATLAB robot toolbox solution method.Secondly,an equivalent model of joint stiffness was developed based on the joint drive system,and the joint stiffness of the robot was measured using modal measurement experiments combined with Adams software.The robot stiffness model was established,and the maximum eigenvalue of the stiffness matrix of the robot end flexibility ellipsoid was used as the robot orientation stiffness evaluation index,and its correctness and reasonableness were verified by finite element simulation analysis.Again,the robot stiffness performance evaluation index is used as the objective function of the mathematical model of the optimisation problem,and the robot posture is optimised under the constant drilling position,so as to achieve the purpose of improving the overall robot stiffness,and the effectiveness and correctness of the optimisation method is verified through simulation analysis.The change of each joint of the robot under the end force is analysed,and it is concluded that the corresponding joint is more affected by the axial force when the end is subjected to the external force;then a joint deformation compensation model is established,and it is verified through experiments that the model can improve the positioning accuracy and reduce the end deformation under the end force.Finally,an evaluation method of the area of the surface tear defect of the drilled hole is proposed for the surface tear of CFRP workpiece.The robot automatic drilling experimental platform was built,and orthogonal test of drilling processing parameters was designed.The optimal process parameters were obtained as follows: presser foot pressure 850 N,spindle speed 3000r/min,and feed speed 60mm/min.Based on the optimized processing parameters,the drilling experiments before and after the robot stiffness optimization were carried out,and the drilling axial force,hole roundness,hole surface tear defects and hole wall roughness before and after the stiffness optimization were analyzed.The results show that the drilling quality can be effectively improved after the robot stiffness optimization.