Research On Semi-active Vibration Control Method For Robotic Milling

With the transformation and upgrading of the manufacturing industry towards intelligence,the advantageous position of industrial robots has gradually become prominent.Industrial robots are widely used in industries such as assembly and processing due to their flexible structure and large workspace.In the field of aerospace,the processing of large parts is not suitable for machine tools,so industrial robots are required to replace machine tools to complete the processing of large aerospace structural parts.However,the serial structure of robots also leads to poor structural rigidity,which is prone to vibration during the working process,affecting the processing quality of parts.In order to solve the vibration problem during robot machining,this paper takes common milling robots as the research object,analyzes the chatter during their milling process,and proposes the application of tuned mass dampers to suppress the chatter during robot milling.The specific research content is as follows:Aiming at COMAU SMART5 NJ 165-3.0 milling robot,the MD-H kinematics model of milling robot is established,and the MD-H parameter table is given;The dynamic modeling method of the robot is explored.The linear torsion spring model is used to simplify the flexible joints of the robot,and the Newton Euler method method is used to establish the dynamic model of the robot;The modal analysis method for the robot was studied,and the theoretical modal analysis of the milling robot was conducted.The experimental modal of the robot was tested through hammer experiments,and the least square method was used to fit.Finally,the first three modes of the robot were obtained.Aiming at the problem of chatter during robotic milling,a semi active tuned mass damper technique was proposed to suppress robot chatter.The vibration suppression principle of tuned mass damper is introduced,and a mathematical model of milling robot tuned mass damper system is established.The optimization design method of milling robot and tuned mass damper is studied.The influence of mass ratio,damping ratio,and natural frequency ratio on vibration suppression effect is analyzed using MATLAB programming.System model of milling robot with tuned mass damper is established using MATLAB/SIMULINK.The vibration suppression effect of tuned mass damper is simulated.Aiming at the low-frequency chatter of robots,a cantilever variable stiffness tuned mass damper(CVS-TMD)design scheme was proposed,and the structural design of CVS-TMD was completed and a physical prototype was implemented;The adaptive vibration frequency control strategy is studied,the corresponding relationship between the cantilever and frequency of CVS-TMD is calibrated,and an adaptive sliding mode controller for CVS-TMD is designed.Aiming at the effectiveness of semi-active tuned mass damper in suppressing robot milling chatter,an experiment on robot milling chatter suppression was conducted.An experimental platform for robotic milling chatter suppression was established,and an experimental scheme for robotic milling chatter suppression was designed.The robot milling process parameters were determined;Multiple sets of CVS-TMD vibration suppression experiments were conducted under different robot postures.The vibration suppression effects were analyzed through FFT transformation,and the surface quality of the workpiece before and after installing CVS-TMD was compared.The final conclusion was that CVS-TMD can effectively suppress low-frequency chatter during robotic milling.