Trajectory Accuracy Compensation And Analysis On Chatter Stability Of Robotic Milling

Machinery manufacturing technology continues to develop currently and industrial robots have gradually expanded and deepened their applications in the field of intelligent manufacturing due to their low cost,high flexibility,and high automation.The integrated machining system composed of industrial robots and electric spindles also has the advantages of large working space and high flexibility than the large-scale CNC machining centers used in machining applications in aerospace,shipbuilding and other fields,especially suitable for the machining of large components.So that the application of industrial robots has received extensive attention.However,chatter,low absolute positioning accuracy and a series of problems caused by the low stiffness characteristics of the serial industrial robot structure have become the key restricting factors for the promotion of robot machining.In order to achieve the stability of the robot's machining,improve its trajectory accuracy,promote the effective improvement of the processing and avoid the chatter hazard,the main research work in this paper is as follows.The kinematic analysis of the robot is a prerequisite for the research of robot-related problems.Based on the standard DH parameter method,this paper establishes the spatial kinematics description of the COMAU industrial robot.By expressing the transformation relationship between the connecting rods and giving mathematical expressions,the positive kinematics problems are deduced and explained.The Jacobian matrix required for the stiffness matrix calculation in the experimental process and stiffness identification is solved,providing the basic theoretical analysis for subsequent research.Identify the stiffness of the robot joints based on the stiffness model.By in-depth analysis of the potential problems of the stiffness identification experiment,experimental conditions of stiffness identification and the experimental parameters such as load force and robot poses are optimized through MATLAB to standardize the selection process of the experiment parameters.Based on the optimization results,the identification experiment is conducted to realize the precise identification of the stiffness matrix.The verification experiment proves the accuracy of the optimization results,which provides relevant parameters for subsequent research.Aiming at the poor absolute positioning accuracy of industrial robots,real-time accuracy compensation on the running trajectory is accomplished.Through the laser tracker which is used to monitor,read and send the target ball position coordinates in real time and C5G OPEN control system of the COMAU robot,an online real-time compensation system for the robot trajectory is established based on the PID control algorithm,realizing the closed-loop compensation of trajectory accuracy in robot motion.The effectiveness of the system has been verified through experiments and it meets the requirements of high-precision trajectory compensation.The chatter stability analysis is carried out for the robot milling.Based on the analysis of the milling force modeling,the experimental modal parameter identification of the system is carried out,and the critical cutting parameters are solved by using it to draw the stability lobe diagram.Select the corresponding milling parameters to perform actual milling experiments to verify the accuracy of the image,and provide a reasonable reference for the selection of parameters for robot milling.