Geometric Error Calibration And Experimental Research Of Propeller Industrial Robot Milling Platform

Marine propeller is one of the important parts of the ship power system,the main means of machining the propeller is currently CNC machine tools.Industrial robots,which have the advantages of high precision,high efficiency and high flexibility,are gradually used in the field of machining.The geometric accuracy and structural rigidity of the robot are the important factors that affect the accuracy of the positioning,then influence the machining precision.Therefore,it is necessary to analyze the geometry and rigidity of the robot.When robots machine complex complex surface features of the propeller,it is need to adopt robot programming off-line.In view of the need for medium-sized propeller machining,the robot's working space is estimated and the power and torque required for the spindle are calculated,and the model of industrial robots and electric spindles are selected.The control system and mechanical integration of the robot machining platform are designed,and then Marine propeller robot milling platform.is established.Taking ABB IRB 6660 robot as the research object,the geometric error of the robot body in Cartesian space and joint space are analyzed.Based on the D-H model,the mapping relationship between the robot end-to-base coordinate system is established,and then the positive and inverse kinematics equation of the robot are derived.Based on the laser tracker to carry out the geometric calibration of the robot,it is necessary to establish the conversion relationship between the coordinate system and the base coordinate system,and the target can not be placed in the center of the robot flange,so the error model based on the distance difference is established.The kinematic parameters of the two groups are calibrated by CPA method and L-M method,and the positioning accuracy of the robot is improved.Based on the traditional stiffness model of the robot,the robot's joint stiffness identification experiment is carried out by means of laser tracker and dynamometer.In the experiment,the appropriate robot postures are selected,and the deformation of the robot end is measured.The deformation and force of the robot end are transformed into the flange coordinate system,and the joint stiffness of the robot is identified.Finally,the deformation of the robot is predicted in the verification experiment,and the correctness of the identification result is verified compared with the actual deformation.At last,In the machining of the propeller,robot off-line programming is carried out.Coordinate systems in the machining platform are analyzed,and the workpiece coordinate system and tool coordinate system are calibrated.Based on UG software the trajectory is carreid out to generate the path file of the propeller machining,and the path flie is transformed into RAPID language,which is derived to verify the correctness of the conversion.Finally,Machining parameters are designed to carry out milling of the non-overlapping area of propeller blade surface.