| As the representative of intelligent manufacturing equipment,industrial robot is the focus of high-end Manufacturing Industry,and its R & D,manufacture and application are the important symbol of a country's science and technology innovation level.At present,the precision of repeated positioning of industrial robot can reach 0.01 mm ? 0.1 mm,but its absolute positioning accuracy is only millimeter.And the research shows that the end stiffness of the industrial robot is only 1 / 50 of that of the NC machine tool,and its absolute positioning accuracy is greatly influenced by the load,so it can not meet the needs of high-end manufacturing tasks.Therefore,this paper takes Staubli TX60 six-axis industrial robot as the research object,and focuses on the research of multi-level calibration technology for high-end manufacturing applications,the calibration of industrial robot is completed from three levels of geometric parameter error,stiffness parameter error and residual error.The purpose is to improve the precision performance of industrial robots in variable load environment,which is expected to promote the wide application of industrial robots in high-end manufacturing and the rapid development of industrial robots industry in China.Firstly,the first level of hierarchical calibration is realized by using CPA,Circle Point Analysis and error model.The absolute positioning error of the industrial robot is reduced by43.99%,which is obviously better than the traditional CPA method.Secondly,for the error model method,the redundant parameter analysis method based on the error sensitivity is used to replace the traditional redundant parameter analysis method,and the position error of the industrial robot is reduced by 80.34% by the pose error model method.At the same time,compared with error model method,the robot calibrated by CPA method has better global characteristics.Secondly,on the basis of geometric parameter calibration,this paper uses joint stiffness calibration method and residual error calibration method based on Chebyshev polynomials fitting to complete stiffness error calibration and residual error calibration of delamination error calibration.The joint stiffness error model successfully reduced the combined position error by53.97% under the applied load.The residual error calibration based on the Chebyshev polynomials finally reduced the integrated position error of the industrial robot by 80.64%,and the model accuracy finally reached 0.0123 mm.The validity of the multi-level calibration method for the position error of the serial industrial robot is proved,which meets the requirement of the high-end manufacturing for the position error of the industrial robot,it provides a good basis for realizing high precision compensation of industrial robot.Finally,the current calibration and measurement system of serial industrial robots is improved by improving the conversion method of basic coordinate system and improving the measurement accuracy of laser tracker by using sequential multi-station measurement method.In view of the shortcomings of the existing methods of base coordinate system transformation,a new method based on multi-point fitting and axis vector measurement is proposed,the experimental results show that the measuring time is reduced to 26.12% of the multi-point fitting method and the conversion error is only 0.215 mm higher than that of the multi-point fitting method,the synthetic error of the conversion is 0.5204 mm,because the base coordinate system will be further corrected in the process of geometric parameter calibration,the higher error is within the allowable range,but the measurement efficiency is greatly improved.In order to improve the precision of industrial robot measurement,the sequential multi-station measurement method is used.The experiment shows that the precision of the measurement method is 0.023 mm,which meets the calibration requirement of large-scale industrial robot,and validates the validity of the measurement method and the measurement system. |
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