Research On The Improvement Of Geometric Accuracy Of Mobile Milling Robot And Cutting Experiment

Combined with the requirements of the new round of industrial revolution of Industry 4.0 for the deep integration of information technology and manufacturing,with the goal of intelligent,flexible and digital manufacturing process,it has great practical significance to improve the overall manufacturing technology level of China's high-end equipment products.The mobile milling robot can achieve large-scale component milling operations.The advantage is that it reduces the number of transfer times of the cabin and the transfer error of the reference,but there are also problems of lower precision and lower processing performance than the machine tool.Therefore,it is very important to study the improvement of robot geometric precision control and processing methods.Geometric accuracy is one of the important indicators for measuring mobile milling robots.Due to the constraints of low positioning accuracy of robots,general industrial robots still cannot meet the accuracy requirements of aerospace manufacturing.In this paper,the geometric precision improvement and cutting experiment of mobile milling robot are proposed.The main research contents are as follows:1)Complete the kinematics modeling of the mobile milling robot,and calibrate the robot body joints,including joint origin calibration and link calibration.According to the D-H theoretical model,the actual length of the robot is measured and calibrated by the laser tracker,and the geometric error of the joint is compensated and a model is established to complete the optimization process.Finally,the geometric accuracy improvement strategy of the mobile milling robot is proposed.2)Complete the calibration of the mobile milling robot,including the calibration of the omnidirectional intelligent mobile platform,the robot body,the end effector flange and the nose of the spindle.By optimizing the calibration method,a plurality of experimental schemes are selected to mill the workpiece,and then the kinematic relationship of the spindle end is placed in numerical control programming to achieve high-precision motion with redundant degrees of freedom.The "pitch compensation method" is used to calibrate the grating scale of the third joint of the mobile milling robot to complete the joint rotation angle compensation,according to the deviation between the actual data and the raster reading value,the rotation accuracy compensation value of the third joint is 0.013°,and finally the compensation table in the Siemens 840 Dsl CNC system is modified.3)Complete the construction of the automatic tool setting system of the KUKA series robot,according to use the automatic tool setting system software platform and carry out the automatic tool setting experiment.An automatic tool setting system was built for the KUKA series robot.The hardware system scheme was designed.The communication connection and parameter configuration were carried out for each part,and the corresponding button and tool setting method of the tool setting device was introduced.Finally,the spatial three-dimensional pose of the tool tip is obtained by automatic tool setting measurement.4)Establish a cutting experiment platform for mobile milling robots and an external measurement system,according to evaluate the accuracy compensation results of the joint rotation angle feedback of the mobile milling robot,and verify the positioning accuracy test.Further experiments on cutting of workpieces after precision compensation of joint rotation angle are carried out.Experimental results show that the compensation scheme enables the flatness error of the mobile milling robot to be stably controlled within 0.03 mm after milling,and the absolute positioning accuracy of the mobile milling robot has been significantly improved.