Research On Mode-coupling Chatter Analysis And Path Optimization Of Robot Milling

Industrial robots have become indispensable core equipment in automated production lines and are widely used in welding,handling,assembly,painting and polishing.In addition,a 6-DOF industrial robot is the main body of motion,and the robot processing system that holds the high-speed spindle at the end has been rapidly developed in the field of material removal.Such robotic processing systems can perform tasks such as milling,boring,grinding and cutting.Compared to traditional CNC machine tools,robotic processing systems have the advantages of high flexibility,large processing area,and low price.However,because the rigidity of the robot structure is weak,chatter vibration is very easy to occur.Therefore,in this paper,taking ABB IRB1200 robot as the research object,starting from the milling chatter of the robot,the mechanism of chatter vibration is analyzed and the robot machining path planning method to avoid chatter is studied.The details are as follows:(1)Summarize the research status of robot machining chatter at home and abroad.Robots differ from machine tools in that their stiffness is much less than 1N/μm,and chatter is one of the major obstacles to the use of robots in machining.(2)Kinematic modeling and analysis of ABB robots.The D-H parameter method was used to establish the coordinate system to obtain the motion equation of the robot,and then a detailed derivation of the Jacobian matrix was performed.(3)Analyze the mechanism of milling chatter in robots.There are two forms of chatter in robot milling,where mode coupling chatter dominates.Based on the criteria of system stability,the conditions forjudging the chatter of robot milling are proposed.(4)Robotic chatter criterion parameter identification for milling.Experiments identify robot structural stiffness,modal analysis experiments determine the natural frequency of the robot structure,and theoretically calculate the stiffness of the robot’s milling process.(5)Optimized selection of passive cutting parameters for robot milling.The singlevariable experiment determines the effects of various parameters(spindle speed,depth of cut,feedrate,tool overhang,forward and reverse milling,cutting materials)on the milling chatter of the robot.(6)Robot path optimization based on stiffness orientation method.By analyzing the chattering mechanism of the robot’s milling process,it is found that different machining paths have a certain influence on whether or not chatter occurs in robot milling.Combining the results of kinematics and modal analysis of the robot,starting from the chatter mechanism,the machining path to avoid or reduce chatter is optimized.