Error Analysis And Compensation Of 3D Laser Ball Bar

The development of intelligent manufacturing,especially in the aviation,automobile and other manufacturing fields,needs more industrial robots and higher positioning accuracy of industrial robots.The motion accuracies of industrial robots are mainly measured by laser trackers.However,the measuring and tracking systems of laser trackers are complicated and manufacturing costs are very high,and the instruments are very difficult to popularize.A kind of passive laser tracking measurement method with simple structure and high accuracy meeting measurement demand of industrial robots was proposed to measure the spatial position accuracy of moving targets,and a kind of passive laser tracker also was developed,which was called 3D laser ball bar.In order to improve the measurement accuracy of 3D laser ball bar,the main error compensation methods were established in this paper.Firstly,according to measuring principle and opto-mechanical structure of 3D laser ball bar,the main error sources are analyzed and the multi-body system error modeling method was used to establish the error compensation model.Secondly,measurement methods of model parameters were proposed.For example,a multi-tooth indexing table and a high precision photoelectric autocollimator were used to calibrate the angular error of the 2D rotary stages.After using harmonic error compensation method to fit the discrete angular error,the angular measurement errors were reduced to ±1".The non-intersection between the standing axis and transit axis was directly measured by the two-face test,and a precision three-axis machine tool was used to measure the base length,the non-perpendicularity between standing axis and transit axis,and the non-perpendicularity between laser axis and transit axis.Finally,a collimator system was developed to measure the motion error of the telescopic device.A direct coordinate calibration experiment was designed and conducted on a precision three-axis machine tools.After errors compensation,the experimental results indicated that the systematic error caused by the non-orthogonality was reduced from 120 ?m to 28 ?m in a plane of 180 mm×180 mm,the positioning error of the X-axis was reduced from 20 ?m to 8 ?m,and the positioning error of the Z-axis was reduced from 60 ?m to 25 ?m.Finally,the measurement program of the 3D laser ball bar was designed based on the C# language.The functions of program consist of the model of data acquisition and processing,the model of coordinate transformations between robots and 3D laser ball bar coordinate,the model of angular error self-calibration and compensation of the two rotary stages,the model of robot spatial error measurement based on the ISO 9283,and the model of dynamic tracking trajectory of robots.The human-machine friendly interactive program also realized real-time display of system measurement results and status of each part.