| With the sustained improvement of China's comprehensive national strength,great accomplishments have been made in space industry.More and more types of large precision optical instruments have been developed,and more stringent requirements have been put forward for the assembly precision of aerospace products.These instruments often have the characteristics of large weight,high precision and complex adjustment process.Recently,the assembly task of products mainly depends on manual operation.Hence,assembly cycle,precision and reliability are strongly affected by the experience of the operators.Therefore,the introduction of large industrial robots into the aerospace manufacturing field and the development of high-precision automatic assembly technology can realize the high precision and reliability of aerospace equipment,and it is an effective way to solve the problems of high-precision assembly of aerospace products.This topic carries out the calibration technology research in the field of automatic assembly of large industrial robot,taking the assembly of space telescope as the background and the large industrial robot KUKA KR1000 Titan as the experimental object.The main research work is as follows:(1)The research status of robot calibration technology in the field of automatic assembly at home and abroad is studied in the topic.Besides,the robot system is introduced into the assembly task in the aerospace field.It improves the assembly efficiency,shortens the production cycle of space equipment,reduces the production cost,and solves the over-reliance of the traditional method on manual assembly experience.(2)The research of the topic completes the kinematics analysis and modeling simulation of the robot.The kinematics model of KUKA KR1000 Titan industrial robot was built by applying the classical D-H modeling method to it,and the forward and inverse kinematics analysis was carried out.The simulation of the established model was carried out by using MATLAB software,and the correctness of the kinematics model was verified.(3)The kinematics calibration model and precision compensation method of large industrial robot are proposed.Based on analysing the sources ofindustrial robots' kinematics parameter errors,the coordinate system transformation error and the target ball installation error were added to the error model,therefore the differential MD-H error model of robots was established,and the calibration model based on the minimum position error was deduced.Then the laser tracker is used to measure the flange connecting the target ball in real time to get the pose of the robot end.Moreover,the L-M algorithm and the L-S method are used to identify the parameters and compare the actual position and theoretical position.(4)Experimental study on robot kinematics calibration.In order to verify the effectiveness of the identification method,a KUKA KR1000 Titan manipulator combined with a Leica laser tracker was applied to complete the kinematics calibration experiment in the laboratory.The actual position and pose data of the end target ball were measured by laser tracker,and the error parameters were identified by using the improved iterative least square method.Finally,the robot was corrected and compensated according to the calculated deviation,and the kinematics calibration process is completed.The results of the experiment indicatethat the average error decreased from 1.122 mm to 0.340 mm and the average deviation has increased by about 70%.The absolute positioning accuracy rate significantly improved with the process of calibration compensation.In conclusion,the proposed calibration and precision compensation method of large industrial robotfor automatic assembly can accurately calculate the parameters in the calibration model,achievingsignificant results in precision compensation.Furthermore,it also has a certain universality,which is of great significance to the calibration and precision compensation of other large industrial robots. |
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