| As a typical representative of advanced manufacturing equipment,six-axis series industrial robot has many advantages,such as multi-degree of freedom,flexible manipulation,multi-function and so on.It is the most widely used and basic manufacturing equipment at domestic and abroad.At present,the main core components and underlying core technology of most domestic robotics enterprises still rely on foreign manufacturers to provide,only through the assembly of the whole machine,application level development to obtain a limited market share.Therefore,the research and manufacture of the key parts of the robot are the key issues to be solved and improved urgently,such as the diversified modeling of the robot,the kinematics error analysis and the performance evaluation of the overall accuracy of the robot.The main purpose of this paper is to find a convenient and easy-to-operate calibration method to improve the accuracy of tool center point of the industrial robots.Kinematics calibration is the most effective method to improve the accuracy of tool center point.Calibration includes:modeling,error measurement,parameter identification and error compensation.How to realize these processes quickly and effectively is a major prerequisite for future industrial robots in high-precision applications.The main technical problems and conclusions of this paper are as follows:1.Establish the MDH kinematical error model based on the roundness error measurement of the double ball bar instrument.Considering about the practical application,the measurement of the double ball bar instrument is convenient and easy to operate,and the another reason is relatively cheap.Establish an error model suitable for this measurement.The planar roundness error measured by a double ball bar is used as an evaluation method for the absolute accuracy of industrial robots.2.To carry out the simulation of kinematics error model algorithm,Jacobian iteration method and least squares method are mainly used to identify the error parameters,and the results of identification are fed back to the joint space for compensation to verify its effectiveness.In the simulation experiment,after four iterations,the average value of the position error vector mode is reduced to nanometer range.3.Develop roundness error measurement and compensation of six-axis industrial robot on the whole working platform,analyze the effect of roundness error compensation in each local plane area,and verify that the measurement of plane roundness error proposed in this paper can be used as an effective calibration method.Through the overall analysis of roundness errors in 30 sub-regions,the best and worst working areas of industrnal robots in the working platform are obtained.The average measurement error of the double ball bar instrument is reduced from 54?m to 7 ?m after calibration,and the standard deviation is reduced from 0.1210mm to 0.0975mm.Laser interferometer was used to verify the position and attitude accuracy of the calibrated end of industrial robot.After calibration,the positioning errors measured by laser interferometer decreased by 10%and 78.8%on the X and Y axes respectively. |
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