Analysis And Solution Of Jittter Oroblems Of Six-axis Tandem Light Robotic Arm-tip

The trajectory accuracy of six-axis tandem robotic arm is one of the important standards for measuring the precision and operating quality of the robotic arm.The jitter of the six-axis tandem robotic arm severely restricts its application in high-precision machining among its many influencing factors.The six-axis tandem light robotic arm is taken as the research object of this article.The jitter of robot arm-tip charecteristics and key influencing factors are systematically studied.And a solution combining mechanical theory and mechanics is proposed.The main research work carried out and completed in this paper are as follows:(1)The jitter signal feature acquisition test at of arm-tip was designed.Acquiring arm-tip jitter acceleration time signal of the robotic under specific conditions based on the LMS Test Lab(?) acoustic test system.The displacement time signal and spectrum function of the arm-tip jitter robot arm are acquired through the signal processing method.The frequency of arm-tip jitter is mainly concentrated at 9.6 Hz and the maximum amplitude of jitter is 0.3 mm.(2)Three experiments to investigate the robot arm-tip jitter were proposed to investigate the key factors that cause arm-tip jitter.First,the modal test of the robot arm and the arm-tip jitter test under different load conditions are disgened.Its used to verify whether the arm-tip jitter is caused by modal resonance.It is found that the natural frequency of the robot arm is different from the jitter frequency.At the same time,the jitter frequency of the arm-tip under different load conditions is still mainly concentrated at about 9.6 Hz.It can be proved that the jitter is not caused by the resonance of the robot arm.Then,the vibration analysis of the robotic arm drive system is performed in the ROS control system.The research found that the main cause of the robot arm-tip jitter is the forced end vibration and caused by the unstable and coupled output of the drive system of the main driving joint of the robotic arm.(3)A solution to the robot arm-tip jitter was proposed.A passive vibration damping method for a two-degree-of-freedom dynamic absorber based on the principle of first-order modal resonance is proposed,given the complexity of the factors that cause robot arm-tip jitter.It can realize the resonance between the robot arm-tip and the vibrator in the shock absorber to achieve the effect of specifically moving the jitter energy at the robot arm-tip.Moreover,it can be installed independently at the robot arm-tip without the need to modify the mechanical arm body.(4)A numerical simulation verification experiment and physical experiment verification of the robot arm-tip reduction is carried out.The influence of the rigidity of the solid joints on the overall stiffness of the robotic arm is studied.An experimental scheme for accurate acquisition of joint stiffness was designed.The two-degree-of-freedom dynamic shock absorber model installed robot arm-tip numerical model is simulated.The actual structure of the shock absorber is designed and installed at the robot arm-tip for field verification.The research results of simulation and experiment show that the vibration damper can reduce the average amplitude of jitter at the robot arm-tip by 50%.