Calibration Of Industrial Robot Based On Relative Error Model And Trajectory Compensation

There are various brands of industrial robots in the market.These robots have the same disadvantage: the repetitive accuracy of robot is good,but the absolute accuracy is bad.Industrial robots are programmable,versatile and efficient.It can be used in many fields,such as laser cutting,spraying,welding,handing,assembling,gauging and so on.With the development of modern manufacturing industry,industrial robots play an irreplaceable role in the process of automation.Therefore,the accuracy of industrial robot is particularly important.It is necessary to calibrate industrial robot to improve the absolute location accuracy of robot.This paper present a calibration method of six-axis robot based on relative error model and trajectory compensation.The position of standard glass sphere is measured in different poses in the workspace by NON-BAR laser measuring equipment installed at the end of robot.Based on the data of measuring,the relative error model is established to solve the kinematics parameter error of robot.Then the results of the kinematics parameter error are applied to actual robot by trajectory compensation.Based on the scheme described above,several problems are studied in this thesis.(1)Robot error measurement based on NON-BAR measurement equipment.In the paper,the six-axis robot is calibrated by the data of offset value and joint angle.The offset value is from NON-BAR and the joint angle is from robot teaching device.The NON-BAR induction probe is clamped at the end of the flange of robot by a fixture.Through controlling the robot,we can measure the offset value of the standard glass sphere in different poses.(2)Establishment of relative error model and solution of robot kinematics parameter errors.This paper establishes the kinematics model of robot based on DH model,and adds the NON-BAR sensor as the seventh joint to the robot kinematics model.Then this paper establishes the relative error model according to the characteristic of NON-BAR,and solves the kinematics parameter error by the least square method.(3)Calibration result compensation scheme based on trajectory compensation.Most industrial robots do not open the right to modify all kinematics parameters,so this paper presents a method to correct the error of the robot by trajectory compensation.With the help of robot off-line programming software,this paper compensates the kinematics parameter errors to the square robot model,and obtains the joint angle by inverse solution.Then the modified trajectory is obtained by substituting the joint angle into the original robot model.Finally,the revised trajectory command is input into the actual robot to improve the accuracy of the robot's end trajectory.